[PATCH v16 00/20] Add generic memory shrinker to VirtIO-GPU and Panfrost DRM drivers

[PATCH v16 00/20] Add generic memory shrinker to VirtIO-GPU and Panfrost DRM drivers

[Dmitry Osipenko]

This series:

  1. Adds common drm-shmem memory shrinker
  2. Enables shrinker for VirtIO-GPU driver
  3. Switches Panfrost driver to the common shrinker
  4. Fixes bugs and improves drm-shmem code

Mesa: https://gitlab.freedesktop.org/digetx/mesa/-/commits/virgl-madvise
IGT:  https://gitlab.freedesktop.org/digetx/igt-gpu-tools/-/commits/virtio-madvise
      https://gitlab.freedesktop.org/digetx/igt-gpu-tools/-/commits/panfrost-madvise

Changelog:

v16:- Added more comments to the code for the new drm-shmem flags

    - Added r-bs from Boris Brezillon

    - Fixed typos and made impovements pointed out by Boris Brezillon

    - Replaced kref with refcount_t as was suggested by Boris Brezillon

    - Corrected placement of got_sgt flag in the Lima driver, also renamed
      flag to got_pages_sgt

    - Removed drm_gem_shmem_resv_assert_held() and made drm_gem_shmem_free()
      to free pages without a new func that doesn't touch resv lock, as was
      suggested by Boris Brezillon

    - Added pages_pin_count to drm_gem_shmem_print_info()

v15:- Moved drm-shmem reference counters to use kref that allows to
      optimize unlocked functions, like was suggested by Boris Brezillon.

    - Changed drm/gem/shmem function names to use _locked postfix and
      dropped the _unlocked, making the naming scheme consistent across
      DRM code, like was suggested by Boris Brezillon.

    - Added patch that fixes UAF in drm-shmem for drivers that import
      dma-buf and then release buffer in the import error code path.

    - Added patch that makes drm-shmem use new flag for SGT's get_pages()
      refcounting, preventing unbalanced refcounting when GEM is freed.

    - Fixed guest blob pinning in virtio-gpu driver that was missed
      previously in the shrinker patch.

    - Moved VC4 and virtio-gpu drivers to use drm_gem_put() in
      GEM-creation error code paths, which is now required by drm-shmem
      and was missed in a previous patch versions.

    - Virtio-GPU now attaches shmem pages to host on first use and not
      when BO is created. In older patch versions there was a potential
      race condition in the BO creation code path where both
      get_sgt()+object_attach() should've been made under same resv lock,
      otherwise pages could be evicted before attachment is invoked.

    - Virtio-GPU and drm-shmem shrinker patches are split into smaller
      ones.

v14:- All the prerequisite reservation locking patches landed upstream,
      previously were a part of this series in v13 and older.

        https://lore.kernel.org/dri-devel/20230529223935.2672495-1-dmitry.osipenko@collabora.com/

    - Added patches to improve locked/unlocked function names, like was
      suggested by Boris Brezillon for v13.

    - Made all exported drm-shmem symbols GPL, like was previously
      discussed with Thomas Zimmermann on this series.

    - Improved virtio-gpu shrinker patch. Now it won't detach purged BO
      when userspace closes GEM. Crosvm (and not qemu) checks res_id on
      CMD_CTX_DETACH_RESOURCE and prints noisy error message if ID is
      invalid, which wasn't noticed before.

v13:- Updated virtio-gpu shrinker patch to use drm_gem_shmem_object_pin()
      directly instead of drm_gem_pin() and dropped patch that exported
      drm_gem_pin() functions, like was requested by Thomas Zimmermann in
      v12.

v12:- Fixed the "no previous prototype for function" warning reported by
      kernel build bot for v11.

    - Fixed the missing reservation lock reported by Intel CI for VGEM
      driver. Other drivers using drm-shmem were affected similarly to
      VGEM. The problem was in the dma-buf attachment code path that led
      to drm-shmem pinning function which assumed the held reservation lock
      by drm_gem_pin(). In the past that code path was causing trouble for
      i915 driver and we've changed the locking scheme for the attachment
      code path in the dma-buf core to let exporters to handle the locking
      themselves. After a closer investigation, I realized that my assumption
      about testing of dma-buf export code path using Panfrost driver was
      incorrect. Now I created additional local test to exrecise the Panfrost
      export path. I also reproduced the issue reported by the Intel CI for
      v10. It's all fixed now by making the drm_gem_shmem_pin() to take the
      resv lock by itself.

    - Patches are based on top of drm-tip, CC'd intel-gfx CI for testing.

v11:- Rebased on a recent linux-next. Added new patch as a result:

        drm/shmem-helper: Export drm_gem_shmem_get_pages_sgt_locked()

        It's needed by the virtio-gpu driver to swap-in/unevict shmem
        object, previously get_pages_sgt() didn't use locking.

    - Separated the "Add memory shrinker" patch into smaller parts to ease
      the reviewing, as was requested by Thomas Zimmermann:

        drm/shmem-helper: Factor out pages alloc/release from
          drm_gem_shmem_get/put_pages()
        drm/shmem-helper: Add pages_pin_count field
        drm/shmem-helper: Switch drm_gem_shmem_vmap/vunmap to use pin/unpin
        drm/shmem-helper: Factor out unpinning part from drm_gem_shmem_purge()

    - Addessed the v10 review comments from Thomas Zimmermann: return errno
      instead of bool, sort code alphabetically, rename function and etc
      minor changes.

    - Added new patch to remove the "map->is_iomem" from drm-shmem, as
      was suggested by Thomas Zimmermann.

    - Added acks and r-b's that were given to v10.

v10:- Was partially applied to misc-fixes/next.

      https://lore.kernel.org/dri-devel/6c16f303-81df-7ebe-85e9-51bb40a8b301@collabora.com/T/

Dmitry Osipenko (20):
  drm/shmem-helper: Fix UAF in error path when freeing SGT of imported
    GEM
  drm/shmem-helper: Use flag for tracking page count bumped by
    get_pages_sgt()
  drm/gem: Change locked/unlocked postfix of drm_gem_v/unmap() function
    names
  drm/gem: Add _locked postfix to functions that have unlocked
    counterpart
  drm/v3d: Replace open-coded drm_gem_shmem_free() with
    drm_gem_object_put()
  drm/virtio: Replace drm_gem_shmem_free() with drm_gem_object_put()
  drm/shmem-helper: Make all exported symbols GPL
  drm/shmem-helper: Refactor locked/unlocked functions
  drm/shmem-helper: Remove obsoleted is_iomem test
  drm/shmem-helper: Add and use pages_pin_count
  drm/shmem-helper: Use refcount_t for pages_use_count
  drm/shmem-helper: Add and use lockless drm_gem_shmem_get_pages()
  drm/shmem-helper: Switch drm_gem_shmem_vmap/vunmap to use pin/unpin
  drm/shmem-helper: Use refcount_t for vmap_use_count
  drm/shmem-helper: Add memory shrinker
  drm/shmem-helper: Export drm_gem_shmem_get_pages_sgt_locked()
  drm/virtio: Pin display framebuffer BO
  drm/virtio: Attach shmem BOs dynamically
  drm/virtio: Support memory shrinking
  drm/panfrost: Switch to generic memory shrinker

 drivers/gpu/drm/drm_client.c                  |   6 +-
 drivers/gpu/drm/drm_gem.c                     |  26 +-
 drivers/gpu/drm/drm_gem_framebuffer_helper.c  |   6 +-
 drivers/gpu/drm/drm_gem_shmem_helper.c        | 596 +++++++++++++++---
 drivers/gpu/drm/drm_internal.h                |   4 +-
 drivers/gpu/drm/drm_prime.c                   |   4 +-
 drivers/gpu/drm/lima/lima_gem.c               |  11 +-
 drivers/gpu/drm/lima/lima_sched.c             |   4 +-
 drivers/gpu/drm/panfrost/Makefile             |   1 -
 drivers/gpu/drm/panfrost/panfrost_device.h    |   4 -
 drivers/gpu/drm/panfrost/panfrost_drv.c       |  29 +-
 drivers/gpu/drm/panfrost/panfrost_dump.c      |   4 +-
 drivers/gpu/drm/panfrost/panfrost_gem.c       |  36 +-
 drivers/gpu/drm/panfrost/panfrost_gem.h       |   9 -
 .../gpu/drm/panfrost/panfrost_gem_shrinker.c  | 122 ----
 drivers/gpu/drm/panfrost/panfrost_job.c       |  18 +-
 drivers/gpu/drm/panfrost/panfrost_mmu.c       |   4 +-
 drivers/gpu/drm/panfrost/panfrost_perfcnt.c   |   6 +-
 drivers/gpu/drm/v3d/v3d_bo.c                  |  26 +-
 drivers/gpu/drm/virtio/virtgpu_drv.h          |  22 +-
 drivers/gpu/drm/virtio/virtgpu_gem.c          |  80 +++
 drivers/gpu/drm/virtio/virtgpu_ioctl.c        |  57 +-
 drivers/gpu/drm/virtio/virtgpu_kms.c          |   8 +
 drivers/gpu/drm/virtio/virtgpu_object.c       | 147 ++++-
 drivers/gpu/drm/virtio/virtgpu_plane.c        |  17 +-
 drivers/gpu/drm/virtio/virtgpu_submit.c       |  15 +-
 drivers/gpu/drm/virtio/virtgpu_vq.c           |  40 ++
 include/drm/drm_device.h                      |  10 +-
 include/drm/drm_gem.h                         |   6 +-
 include/drm/drm_gem_shmem_helper.h            | 141 ++++-
 include/uapi/drm/virtgpu_drm.h                |  14 +
 31 files changed, 1095 insertions(+), 378 deletions(-)
 delete mode 100644 drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c

-- 
2.41.0

[PATCH v16 01/20] drm/shmem-helper: Fix UAF in error path when freeing SGT of imported GEM

[Dmitry Osipenko]

Freeing drm-shmem GEM right after creating it using
drm_gem_shmem_prime_import_sg_table() frees SGT of the imported dma-buf
and then dma-buf frees this SGT second time.

The v3d_prime_import_sg_table() is example of a error code path where
dma-buf's SGT is freed by drm-shmem and then it's freed second time by
dma_buf_unmap_attachment() in drm_gem_prime_import_dev().

Add drm-shmem GEM flag telling that this is imported SGT shall not be
treated as own SGT, fixing the use-after-free bug.

Cc: stable@vger.kernel.org
Fixes: 2194a63a818d ("drm: Add library for shmem backed GEM objects")
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 13 ++++++++++++-
 include/drm/drm_gem_shmem_helper.h     |  7 +++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index e435f986cd13..6693d4061ca1 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -141,7 +141,7 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
 
 	if (obj->import_attach) {
 		drm_prime_gem_destroy(obj, shmem->sgt);
-	} else {
+	} else if (!shmem->imported_sgt) {
 		dma_resv_lock(shmem->base.resv, NULL);
 
 		drm_WARN_ON(obj->dev, shmem->vmap_use_count);
@@ -765,6 +765,17 @@ drm_gem_shmem_prime_import_sg_table(struct drm_device *dev,
 
 	shmem->sgt = sgt;
 
+	/*
+	 * drm_gem_shmem_prime_import_sg_table() can be called from a
+	 * driver specific ->import_sg_table() implementations that
+	 * may fail, in that case drm_gem_shmem_free() will be invoked
+	 * without assigned drm_gem_object::import_attach.
+	 *
+	 * This flag lets drm_gem_shmem_free() differentiate whether
+	 * SGT belongs to dmabuf and shall not be freed by drm-shmem.
+	 */
+	shmem->imported_sgt = true;
+
 	drm_dbg_prime(dev, "size = %zu\n", size);
 
 	return &shmem->base;
diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
index bf0c31aa8fbe..ec70a98a8fe1 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -73,6 +73,13 @@ struct drm_gem_shmem_object {
 	 */
 	unsigned int vmap_use_count;
 
+	/**
+	 * @imported_sgt:
+	 *
+	 * True if SG table belongs to imported dma-buf.
+	 */
+	bool imported_sgt : 1;
+
 	/**
 	 * @pages_mark_dirty_on_put:
 	 *
-- 
2.41.0

[PATCH v16 02/20] drm/shmem-helper: Use flag for tracking page count bumped by get_pages_sgt()

[Dmitry Osipenko]

Use separate flag for tracking page count bumped by shmem->sgt to avoid
imbalanced page counter during of drm_gem_shmem_free() time. It's fragile
to assume that populated shmem->pages at a freeing time means that the
count was bumped by drm_gem_shmem_get_pages_sgt(), using a flag removes
the ambiguity.

Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 11 ++++++++++-
 drivers/gpu/drm/lima/lima_gem.c        |  1 +
 include/drm/drm_gem_shmem_helper.h     |  7 +++++++
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 6693d4061ca1..848435e08eb2 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -152,8 +152,10 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
 			sg_free_table(shmem->sgt);
 			kfree(shmem->sgt);
 		}
-		if (shmem->pages)
+		if (shmem->pages) {
 			drm_gem_shmem_put_pages(shmem);
+			drm_WARN_ON(obj->dev, !shmem->got_pages_sgt);
+		}
 
 		drm_WARN_ON(obj->dev, shmem->pages_use_count);
 
@@ -693,6 +695,13 @@ static struct sg_table *drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_
 	if (ret)
 		goto err_free_sgt;
 
+	/*
+	 * This flag prevents imbalanced pages_use_count during
+	 * drm_gem_shmem_free(), where pages_use_count=1 only if
+	 * drm_gem_shmem_get_pages_sgt() was used by a driver.
+	 */
+	shmem->got_pages_sgt = true;
+
 	shmem->sgt = sgt;
 
 	return sgt;
diff --git a/drivers/gpu/drm/lima/lima_gem.c b/drivers/gpu/drm/lima/lima_gem.c
index 4f9736e5f929..67c39b95e30e 100644
--- a/drivers/gpu/drm/lima/lima_gem.c
+++ b/drivers/gpu/drm/lima/lima_gem.c
@@ -48,6 +48,7 @@ int lima_heap_alloc(struct lima_bo *bo, struct lima_vm *vm)
 
 		bo->base.pages = pages;
 		bo->base.pages_use_count = 1;
+		bo->base.got_pages_sgt = true;
 
 		mapping_set_unevictable(mapping);
 	}
diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
index ec70a98a8fe1..a53c0874b3c4 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -73,6 +73,13 @@ struct drm_gem_shmem_object {
 	 */
 	unsigned int vmap_use_count;
 
+	/**
+	 * @got_pages_sgt:
+	 *
+	 * True if SG table was retrieved using drm_gem_shmem_get_pages_sgt()
+	 */
+	bool got_pages_sgt : 1;
+
 	/**
 	 * @imported_sgt:
 	 *
-- 
2.41.0

Re: [PATCH v16 02/20] drm/shmem-helper: Use flag for tracking page count bumped by get_pages_sgt()

[Boris Brezillon]

On Sun,  3 Sep 2023 20:07:18 +0300
Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:

> Use separate flag for tracking page count bumped by shmem->sgt to avoid
> imbalanced page counter during of drm_gem_shmem_free() time. It's fragile
> to assume that populated shmem->pages at a freeing time means that the
> count was bumped by drm_gem_shmem_get_pages_sgt(), using a flag removes
> the ambiguity.
> 
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> ---
>  drivers/gpu/drm/drm_gem_shmem_helper.c | 11 ++++++++++-
>  drivers/gpu/drm/lima/lima_gem.c        |  1 +
>  include/drm/drm_gem_shmem_helper.h     |  7 +++++++
>  3 files changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index 6693d4061ca1..848435e08eb2 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -152,8 +152,10 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
>  			sg_free_table(shmem->sgt);
>  			kfree(shmem->sgt);
>  		}
> -		if (shmem->pages)
> +		if (shmem->pages) {
>  			drm_gem_shmem_put_pages(shmem);
> +			drm_WARN_ON(obj->dev, !shmem->got_pages_sgt);
> +		}

Already mentioned in v15, but I keep thinking the following:

		if (shmem->sgt) {
			// existing code in the preceding
			// if (shmem->sgt) branch
			...

			/*
			 * Release the implicit pages ref taken in
			 * drm_gem_shmem_get_pages_sgt_locked().
			 */
			drm_gem_shmem_put_pages(shmem);
		}

does exactly the same without requiring the addition of a new field.

>  
>  		drm_WARN_ON(obj->dev, shmem->pages_use_count);
>  
> @@ -693,6 +695,13 @@ static struct sg_table *drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_
>  	if (ret)
>  		goto err_free_sgt;
>  
> +	/*
> +	 * This flag prevents imbalanced pages_use_count during
> +	 * drm_gem_shmem_free(), where pages_use_count=1 only if
> +	 * drm_gem_shmem_get_pages_sgt() was used by a driver.
> +	 */
> +	shmem->got_pages_sgt = true;
> +
>  	shmem->sgt = sgt;
>  
>  	return sgt;
> diff --git a/drivers/gpu/drm/lima/lima_gem.c b/drivers/gpu/drm/lima/lima_gem.c
> index 4f9736e5f929..67c39b95e30e 100644
> --- a/drivers/gpu/drm/lima/lima_gem.c
> +++ b/drivers/gpu/drm/lima/lima_gem.c
> @@ -48,6 +48,7 @@ int lima_heap_alloc(struct lima_bo *bo, struct lima_vm *vm)
>  
>  		bo->base.pages = pages;
>  		bo->base.pages_use_count = 1;
> +		bo->base.got_pages_sgt = true;
>  
>  		mapping_set_unevictable(mapping);
>  	}
> diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
> index ec70a98a8fe1..a53c0874b3c4 100644
> --- a/include/drm/drm_gem_shmem_helper.h
> +++ b/include/drm/drm_gem_shmem_helper.h
> @@ -73,6 +73,13 @@ struct drm_gem_shmem_object {
>  	 */
>  	unsigned int vmap_use_count;
>  
> +	/**
> +	 * @got_pages_sgt:
> +	 *
> +	 * True if SG table was retrieved using drm_gem_shmem_get_pages_sgt()
> +	 */
> +	bool got_pages_sgt : 1;
> +
>  	/**
>  	 * @imported_sgt:
>  	 *

Re: [PATCH v16 02/20] drm/shmem-helper: Use flag for tracking page count bumped by get_pages_sgt()

[Dmitry Osipenko]

On 9/5/23 10:40, Boris Brezillon wrote:
> On Sun,  3 Sep 2023 20:07:18 +0300
> Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
> 
>> Use separate flag for tracking page count bumped by shmem->sgt to avoid
>> imbalanced page counter during of drm_gem_shmem_free() time. It's fragile
>> to assume that populated shmem->pages at a freeing time means that the
>> count was bumped by drm_gem_shmem_get_pages_sgt(), using a flag removes
>> the ambiguity.
>>
>> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
>> ---
>>  drivers/gpu/drm/drm_gem_shmem_helper.c | 11 ++++++++++-
>>  drivers/gpu/drm/lima/lima_gem.c        |  1 +
>>  include/drm/drm_gem_shmem_helper.h     |  7 +++++++
>>  3 files changed, 18 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
>> index 6693d4061ca1..848435e08eb2 100644
>> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
>> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
>> @@ -152,8 +152,10 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
>>  			sg_free_table(shmem->sgt);
>>  			kfree(shmem->sgt);
>>  		}
>> -		if (shmem->pages)
>> +		if (shmem->pages) {
>>  			drm_gem_shmem_put_pages(shmem);
>> +			drm_WARN_ON(obj->dev, !shmem->got_pages_sgt);
>> +		}
> 
> Already mentioned in v15, but I keep thinking the following:
> 
> 		if (shmem->sgt) {
> 			// existing code in the preceding
> 			// if (shmem->sgt) branch
> 			...
> 
> 			/*
> 			 * Release the implicit pages ref taken in
> 			 * drm_gem_shmem_get_pages_sgt_locked().
> 			 */
> 			drm_gem_shmem_put_pages(shmem);
> 		}
> 
> does exactly the same without requiring the addition of a new field.

I'll factor out these "flag" patches into separate patchset since they
cause too many questions. This is a fix for a minor bug that existed for
many years and is difficult to trigger in practice, it can wait.

For now will be better to focus on finishing and landing the refcnt and
shrinker patches, the rest of drm-shmem core improvements can be done
afterwards.

-- 
Best regards,
Dmitry

Re: [PATCH v16 02/20] drm/shmem-helper: Use flag for tracking page count bumped by get_pages_sgt()

[Boris Brezillon]

On Tue, 12 Sep 2023 02:41:58 +0300
Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:

> On 9/5/23 10:40, Boris Brezillon wrote:
> > On Sun,  3 Sep 2023 20:07:18 +0300
> > Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
> >   
> >> Use separate flag for tracking page count bumped by shmem->sgt to avoid
> >> imbalanced page counter during of drm_gem_shmem_free() time. It's fragile
> >> to assume that populated shmem->pages at a freeing time means that the
> >> count was bumped by drm_gem_shmem_get_pages_sgt(), using a flag removes
> >> the ambiguity.
> >>
> >> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> >> ---
> >>  drivers/gpu/drm/drm_gem_shmem_helper.c | 11 ++++++++++-
> >>  drivers/gpu/drm/lima/lima_gem.c        |  1 +
> >>  include/drm/drm_gem_shmem_helper.h     |  7 +++++++
> >>  3 files changed, 18 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> >> index 6693d4061ca1..848435e08eb2 100644
> >> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> >> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> >> @@ -152,8 +152,10 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
> >>  			sg_free_table(shmem->sgt);
> >>  			kfree(shmem->sgt);
> >>  		}
> >> -		if (shmem->pages)
> >> +		if (shmem->pages) {
> >>  			drm_gem_shmem_put_pages(shmem);
> >> +			drm_WARN_ON(obj->dev, !shmem->got_pages_sgt);
> >> +		}  
> > 
> > Already mentioned in v15, but I keep thinking the following:
> > 
> > 		if (shmem->sgt) {
> > 			// existing code in the preceding
> > 			// if (shmem->sgt) branch
> > 			...
> > 
> > 			/*
> > 			 * Release the implicit pages ref taken in
> > 			 * drm_gem_shmem_get_pages_sgt_locked().
> > 			 */
> > 			drm_gem_shmem_put_pages(shmem);
> > 		}
> > 
> > does exactly the same without requiring the addition of a new field.  
> 
> I'll factor out these "flag" patches into separate patchset since they
> cause too many questions.

So patch 1 and 2 in this series right?

> This is a fix for a minor bug that existed for
> many years

I'm not denying the fact there's a bug, but I'm convinced this can be
fixed without adding new flags. If there's something wrong with the
suggested solution, I'd be interested to hear more about it.

> and is difficult to trigger in practice, it can wait.

Triggering it with a real fault is hard, but you can manually fake
errors at any point in the initialization process and check what
happens.

> 
> For now will be better to focus on finishing and landing the refcnt and
> shrinker patches, the rest of drm-shmem core improvements can be done
> afterwards.
> 

Sounds good to me.

[PATCH v16 03/20] drm/gem: Change locked/unlocked postfix of drm_gem_v/unmap() function names

[Dmitry Osipenko]

Make drm/gem API function names consistent by having locked function
use the _locked postfix in the name, while the unlocked variants don't
use the _unlocked postfix. Rename drm_gem_v/unmap() function names to
make them consistent with the rest of the API functions.

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/drm_client.c                 |  6 +++---
 drivers/gpu/drm/drm_gem.c                    | 20 ++++++++++----------
 drivers/gpu/drm/drm_gem_framebuffer_helper.c |  6 +++---
 drivers/gpu/drm/drm_internal.h               |  4 ++--
 drivers/gpu/drm/drm_prime.c                  |  4 ++--
 drivers/gpu/drm/lima/lima_sched.c            |  4 ++--
 drivers/gpu/drm/panfrost/panfrost_dump.c     |  4 ++--
 drivers/gpu/drm/panfrost/panfrost_perfcnt.c  |  6 +++---
 include/drm/drm_gem.h                        |  4 ++--
 9 files changed, 29 insertions(+), 29 deletions(-)

diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c
index 037e36f2049c..29306657117a 100644
--- a/drivers/gpu/drm/drm_client.c
+++ b/drivers/gpu/drm/drm_client.c
@@ -265,7 +265,7 @@ void drm_client_dev_restore(struct drm_device *dev)
 static void drm_client_buffer_delete(struct drm_client_buffer *buffer)
 {
 	if (buffer->gem) {
-		drm_gem_vunmap_unlocked(buffer->gem, &buffer->map);
+		drm_gem_vunmap(buffer->gem, &buffer->map);
 		drm_gem_object_put(buffer->gem);
 	}
 
@@ -349,7 +349,7 @@ drm_client_buffer_vmap(struct drm_client_buffer *buffer,
 	 * fd_install step out of the driver backend hooks, to make that
 	 * final step optional for internal users.
 	 */
-	ret = drm_gem_vmap_unlocked(buffer->gem, map);
+	ret = drm_gem_vmap(buffer->gem, map);
 	if (ret)
 		return ret;
 
@@ -371,7 +371,7 @@ void drm_client_buffer_vunmap(struct drm_client_buffer *buffer)
 {
 	struct iosys_map *map = &buffer->map;
 
-	drm_gem_vunmap_unlocked(buffer->gem, map);
+	drm_gem_vunmap(buffer->gem, map);
 }
 EXPORT_SYMBOL(drm_client_buffer_vunmap);
 
diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index 6129b89bb366..fae5832bb0bd 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -1173,7 +1173,7 @@ void drm_gem_unpin(struct drm_gem_object *obj)
 		obj->funcs->unpin(obj);
 }
 
-int drm_gem_vmap(struct drm_gem_object *obj, struct iosys_map *map)
+int drm_gem_vmap_locked(struct drm_gem_object *obj, struct iosys_map *map)
 {
 	int ret;
 
@@ -1190,9 +1190,9 @@ int drm_gem_vmap(struct drm_gem_object *obj, struct iosys_map *map)
 
 	return 0;
 }
-EXPORT_SYMBOL(drm_gem_vmap);
+EXPORT_SYMBOL(drm_gem_vmap_locked);
 
-void drm_gem_vunmap(struct drm_gem_object *obj, struct iosys_map *map)
+void drm_gem_vunmap_locked(struct drm_gem_object *obj, struct iosys_map *map)
 {
 	dma_resv_assert_held(obj->resv);
 
@@ -1205,27 +1205,27 @@ void drm_gem_vunmap(struct drm_gem_object *obj, struct iosys_map *map)
 	/* Always set the mapping to NULL. Callers may rely on this. */
 	iosys_map_clear(map);
 }
-EXPORT_SYMBOL(drm_gem_vunmap);
+EXPORT_SYMBOL(drm_gem_vunmap_locked);
 
-int drm_gem_vmap_unlocked(struct drm_gem_object *obj, struct iosys_map *map)
+int drm_gem_vmap(struct drm_gem_object *obj, struct iosys_map *map)
 {
 	int ret;
 
 	dma_resv_lock(obj->resv, NULL);
-	ret = drm_gem_vmap(obj, map);
+	ret = drm_gem_vmap_locked(obj, map);
 	dma_resv_unlock(obj->resv);
 
 	return ret;
 }
-EXPORT_SYMBOL(drm_gem_vmap_unlocked);
+EXPORT_SYMBOL(drm_gem_vmap);
 
-void drm_gem_vunmap_unlocked(struct drm_gem_object *obj, struct iosys_map *map)
+void drm_gem_vunmap(struct drm_gem_object *obj, struct iosys_map *map)
 {
 	dma_resv_lock(obj->resv, NULL);
-	drm_gem_vunmap(obj, map);
+	drm_gem_vunmap_locked(obj, map);
 	dma_resv_unlock(obj->resv);
 }
-EXPORT_SYMBOL(drm_gem_vunmap_unlocked);
+EXPORT_SYMBOL(drm_gem_vunmap);
 
 /**
  * drm_gem_lock_reservations - Sets up the ww context and acquires
diff --git a/drivers/gpu/drm/drm_gem_framebuffer_helper.c b/drivers/gpu/drm/drm_gem_framebuffer_helper.c
index 3bdb6ba37ff4..3808f47310bf 100644
--- a/drivers/gpu/drm/drm_gem_framebuffer_helper.c
+++ b/drivers/gpu/drm/drm_gem_framebuffer_helper.c
@@ -362,7 +362,7 @@ int drm_gem_fb_vmap(struct drm_framebuffer *fb, struct iosys_map *map,
 			ret = -EINVAL;
 			goto err_drm_gem_vunmap;
 		}
-		ret = drm_gem_vmap_unlocked(obj, &map[i]);
+		ret = drm_gem_vmap(obj, &map[i]);
 		if (ret)
 			goto err_drm_gem_vunmap;
 	}
@@ -384,7 +384,7 @@ int drm_gem_fb_vmap(struct drm_framebuffer *fb, struct iosys_map *map,
 		obj = drm_gem_fb_get_obj(fb, i);
 		if (!obj)
 			continue;
-		drm_gem_vunmap_unlocked(obj, &map[i]);
+		drm_gem_vunmap(obj, &map[i]);
 	}
 	return ret;
 }
@@ -411,7 +411,7 @@ void drm_gem_fb_vunmap(struct drm_framebuffer *fb, struct iosys_map *map)
 			continue;
 		if (iosys_map_is_null(&map[i]))
 			continue;
-		drm_gem_vunmap_unlocked(obj, &map[i]);
+		drm_gem_vunmap(obj, &map[i]);
 	}
 }
 EXPORT_SYMBOL(drm_gem_fb_vunmap);
diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
index ba12acd55139..243d9aa52881 100644
--- a/drivers/gpu/drm/drm_internal.h
+++ b/drivers/gpu/drm/drm_internal.h
@@ -175,8 +175,8 @@ void drm_gem_print_info(struct drm_printer *p, unsigned int indent,
 
 int drm_gem_pin(struct drm_gem_object *obj);
 void drm_gem_unpin(struct drm_gem_object *obj);
-int drm_gem_vmap(struct drm_gem_object *obj, struct iosys_map *map);
-void drm_gem_vunmap(struct drm_gem_object *obj, struct iosys_map *map);
+int drm_gem_vmap_locked(struct drm_gem_object *obj, struct iosys_map *map);
+void drm_gem_vunmap_locked(struct drm_gem_object *obj, struct iosys_map *map);
 
 /* drm_debugfs.c drm_debugfs_crc.c */
 #if defined(CONFIG_DEBUG_FS)
diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 63b709a67471..57ac5623f09a 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -682,7 +682,7 @@ int drm_gem_dmabuf_vmap(struct dma_buf *dma_buf, struct iosys_map *map)
 {
 	struct drm_gem_object *obj = dma_buf->priv;
 
-	return drm_gem_vmap(obj, map);
+	return drm_gem_vmap_locked(obj, map);
 }
 EXPORT_SYMBOL(drm_gem_dmabuf_vmap);
 
@@ -698,7 +698,7 @@ void drm_gem_dmabuf_vunmap(struct dma_buf *dma_buf, struct iosys_map *map)
 {
 	struct drm_gem_object *obj = dma_buf->priv;
 
-	drm_gem_vunmap(obj, map);
+	drm_gem_vunmap_locked(obj, map);
 }
 EXPORT_SYMBOL(drm_gem_dmabuf_vunmap);
 
diff --git a/drivers/gpu/drm/lima/lima_sched.c b/drivers/gpu/drm/lima/lima_sched.c
index ffd91a5ee299..843487128544 100644
--- a/drivers/gpu/drm/lima/lima_sched.c
+++ b/drivers/gpu/drm/lima/lima_sched.c
@@ -371,7 +371,7 @@ static void lima_sched_build_error_task_list(struct lima_sched_task *task)
 		} else {
 			buffer_chunk->size = lima_bo_size(bo);
 
-			ret = drm_gem_vmap_unlocked(&bo->base.base, &map);
+			ret = drm_gem_vmap(&bo->base.base, &map);
 			if (ret) {
 				kvfree(et);
 				goto out;
@@ -379,7 +379,7 @@ static void lima_sched_build_error_task_list(struct lima_sched_task *task)
 
 			memcpy(buffer_chunk + 1, map.vaddr, buffer_chunk->size);
 
-			drm_gem_vunmap_unlocked(&bo->base.base, &map);
+			drm_gem_vunmap(&bo->base.base, &map);
 		}
 
 		buffer_chunk = (void *)(buffer_chunk + 1) + buffer_chunk->size;
diff --git a/drivers/gpu/drm/panfrost/panfrost_dump.c b/drivers/gpu/drm/panfrost/panfrost_dump.c
index e7942ac449c6..0f30bbea9895 100644
--- a/drivers/gpu/drm/panfrost/panfrost_dump.c
+++ b/drivers/gpu/drm/panfrost/panfrost_dump.c
@@ -209,7 +209,7 @@ void panfrost_core_dump(struct panfrost_job *job)
 			goto dump_header;
 		}
 
-		ret = drm_gem_vmap_unlocked(&bo->base.base, &map);
+		ret = drm_gem_vmap(&bo->base.base, &map);
 		if (ret) {
 			dev_err(pfdev->dev, "Panfrost Dump: couldn't map Buffer Object\n");
 			iter.hdr->bomap.valid = 0;
@@ -236,7 +236,7 @@ void panfrost_core_dump(struct panfrost_job *job)
 		vaddr = map.vaddr;
 		memcpy(iter.data, vaddr, bo->base.base.size);
 
-		drm_gem_vunmap_unlocked(&bo->base.base, &map);
+		drm_gem_vunmap(&bo->base.base, &map);
 
 		iter.hdr->bomap.valid = 1;
 
diff --git a/drivers/gpu/drm/panfrost/panfrost_perfcnt.c b/drivers/gpu/drm/panfrost/panfrost_perfcnt.c
index ba9b6e2b2636..52befead08c6 100644
--- a/drivers/gpu/drm/panfrost/panfrost_perfcnt.c
+++ b/drivers/gpu/drm/panfrost/panfrost_perfcnt.c
@@ -106,7 +106,7 @@ static int panfrost_perfcnt_enable_locked(struct panfrost_device *pfdev,
 		goto err_close_bo;
 	}
 
-	ret = drm_gem_vmap_unlocked(&bo->base, &map);
+	ret = drm_gem_vmap(&bo->base, &map);
 	if (ret)
 		goto err_put_mapping;
 	perfcnt->buf = map.vaddr;
@@ -165,7 +165,7 @@ static int panfrost_perfcnt_enable_locked(struct panfrost_device *pfdev,
 	return 0;
 
 err_vunmap:
-	drm_gem_vunmap_unlocked(&bo->base, &map);
+	drm_gem_vunmap(&bo->base, &map);
 err_put_mapping:
 	panfrost_gem_mapping_put(perfcnt->mapping);
 err_close_bo:
@@ -195,7 +195,7 @@ static int panfrost_perfcnt_disable_locked(struct panfrost_device *pfdev,
 		  GPU_PERFCNT_CFG_MODE(GPU_PERFCNT_CFG_MODE_OFF));
 
 	perfcnt->user = NULL;
-	drm_gem_vunmap_unlocked(&perfcnt->mapping->obj->base.base, &map);
+	drm_gem_vunmap(&perfcnt->mapping->obj->base.base, &map);
 	perfcnt->buf = NULL;
 	panfrost_gem_close(&perfcnt->mapping->obj->base.base, file_priv);
 	panfrost_mmu_as_put(pfdev, perfcnt->mapping->mmu);
diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
index bc9f6aa2f3fe..110a9c0ea42b 100644
--- a/include/drm/drm_gem.h
+++ b/include/drm/drm_gem.h
@@ -518,8 +518,8 @@ struct page **drm_gem_get_pages(struct drm_gem_object *obj);
 void drm_gem_put_pages(struct drm_gem_object *obj, struct page **pages,
 		bool dirty, bool accessed);
 
-int drm_gem_vmap_unlocked(struct drm_gem_object *obj, struct iosys_map *map);
-void drm_gem_vunmap_unlocked(struct drm_gem_object *obj, struct iosys_map *map);
+int drm_gem_vmap(struct drm_gem_object *obj, struct iosys_map *map);
+void drm_gem_vunmap(struct drm_gem_object *obj, struct iosys_map *map);
 
 int drm_gem_objects_lookup(struct drm_file *filp, void __user *bo_handles,
 			   int count, struct drm_gem_object ***objs_out);
-- 
2.41.0

[PATCH v16 04/20] drm/gem: Add _locked postfix to functions that have unlocked counterpart

[Dmitry Osipenko]

Add _locked postfix to drm_gem functions that have unlocked counterpart
functions to make GEM functions naming more consistent and intuitive in
regards to the locking requirements.

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/drm_gem.c | 6 +++---
 include/drm/drm_gem.h     | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index fae5832bb0bd..8c0268944199 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -1488,10 +1488,10 @@ drm_gem_lru_scan(struct drm_gem_lru *lru,
 EXPORT_SYMBOL(drm_gem_lru_scan);
 
 /**
- * drm_gem_evict - helper to evict backing pages for a GEM object
+ * drm_gem_evict_locked - helper to evict backing pages for a GEM object
  * @obj: obj in question
  */
-int drm_gem_evict(struct drm_gem_object *obj)
+int drm_gem_evict_locked(struct drm_gem_object *obj)
 {
 	dma_resv_assert_held(obj->resv);
 
@@ -1503,4 +1503,4 @@ int drm_gem_evict(struct drm_gem_object *obj)
 
 	return 0;
 }
-EXPORT_SYMBOL(drm_gem_evict);
+EXPORT_SYMBOL(drm_gem_evict_locked);
diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
index 110a9c0ea42b..d8dedb1f0968 100644
--- a/include/drm/drm_gem.h
+++ b/include/drm/drm_gem.h
@@ -542,7 +542,7 @@ unsigned long drm_gem_lru_scan(struct drm_gem_lru *lru,
 			       unsigned long *remaining,
 			       bool (*shrink)(struct drm_gem_object *obj));
 
-int drm_gem_evict(struct drm_gem_object *obj);
+int drm_gem_evict_locked(struct drm_gem_object *obj);
 
 #ifdef CONFIG_LOCKDEP
 /**
-- 
2.41.0

[PATCH v16 05/20] drm/v3d: Replace open-coded drm_gem_shmem_free() with drm_gem_object_put()

[Dmitry Osipenko]

The drm_gem_shmem_free() doesn't put GEM's kref to zero, which becomes
important with addition of the shrinker support to drm-shmem that will
use kref=0 in order to prevent taking lock during special GEM-freeing
time in order to avoid spurious lockdep warning about locking ordering
vs fs_reclaim code paths.

Replace open-coded drm_gem_shmem_free() with drm_gem_object_put() that
drops kref to zero before freeing GEM.

Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/v3d/v3d_bo.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/v3d/v3d_bo.c b/drivers/gpu/drm/v3d/v3d_bo.c
index 8b3229a37c6d..70c1095d6eec 100644
--- a/drivers/gpu/drm/v3d/v3d_bo.c
+++ b/drivers/gpu/drm/v3d/v3d_bo.c
@@ -33,16 +33,18 @@ void v3d_free_object(struct drm_gem_object *obj)
 	struct v3d_dev *v3d = to_v3d_dev(obj->dev);
 	struct v3d_bo *bo = to_v3d_bo(obj);
 
-	v3d_mmu_remove_ptes(bo);
+	if (drm_mm_node_allocated(&bo->node)) {
+		v3d_mmu_remove_ptes(bo);
 
-	mutex_lock(&v3d->bo_lock);
-	v3d->bo_stats.num_allocated--;
-	v3d->bo_stats.pages_allocated -= obj->size >> PAGE_SHIFT;
-	mutex_unlock(&v3d->bo_lock);
+		mutex_lock(&v3d->bo_lock);
+		v3d->bo_stats.num_allocated--;
+		v3d->bo_stats.pages_allocated -= obj->size >> PAGE_SHIFT;
+		mutex_unlock(&v3d->bo_lock);
 
-	spin_lock(&v3d->mm_lock);
-	drm_mm_remove_node(&bo->node);
-	spin_unlock(&v3d->mm_lock);
+		spin_lock(&v3d->mm_lock);
+		drm_mm_remove_node(&bo->node);
+		spin_unlock(&v3d->mm_lock);
+	}
 
 	/* GPU execution may have dirtied any pages in the BO. */
 	bo->base.pages_mark_dirty_on_put = true;
@@ -142,7 +144,7 @@ struct v3d_bo *v3d_bo_create(struct drm_device *dev, struct drm_file *file_priv,
 	return bo;
 
 free_obj:
-	drm_gem_shmem_free(shmem_obj);
+	drm_gem_object_put(&shmem_obj->base);
 	return ERR_PTR(ret);
 }
 
@@ -160,7 +162,7 @@ v3d_prime_import_sg_table(struct drm_device *dev,
 
 	ret = v3d_bo_create_finish(obj);
 	if (ret) {
-		drm_gem_shmem_free(&to_v3d_bo(obj)->base);
+		drm_gem_object_put(obj);
 		return ERR_PTR(ret);
 	}
 
-- 
2.41.0

Re: [PATCH v16 05/20] drm/v3d: Replace open-coded drm_gem_shmem_free() with drm_gem_object_put()

[Boris Brezillon]

On Sun,  3 Sep 2023 20:07:21 +0300
Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:

> The drm_gem_shmem_free() doesn't put GEM's kref to zero, which becomes
> important with addition of the shrinker support to drm-shmem that will
> use kref=0 in order to prevent taking lock during special GEM-freeing
> time in order to avoid spurious lockdep warning about locking ordering
> vs fs_reclaim code paths.

As for patch 4, I don't mind the change (I actually think it's better
to have a single error path with a free function handling partially
initialized GEM objects, which is exactly what your patch is doing), but
I disagree with the explanation, especially after you dropped
"drm/shmem-helper: Add and use drm_gem_shmem_resv_assert_held() helper"
and went for a drm_gem_shmem_do_release_pages_locked() helper called in
drm_gem_shmem_free().

> 
> Replace open-coded drm_gem_shmem_free() with drm_gem_object_put() that
> drops kref to zero before freeing GEM.
> 
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> ---
>  drivers/gpu/drm/v3d/v3d_bo.c | 22 ++++++++++++----------
>  1 file changed, 12 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/v3d/v3d_bo.c b/drivers/gpu/drm/v3d/v3d_bo.c
> index 8b3229a37c6d..70c1095d6eec 100644
> --- a/drivers/gpu/drm/v3d/v3d_bo.c
> +++ b/drivers/gpu/drm/v3d/v3d_bo.c
> @@ -33,16 +33,18 @@ void v3d_free_object(struct drm_gem_object *obj)
>  	struct v3d_dev *v3d = to_v3d_dev(obj->dev);
>  	struct v3d_bo *bo = to_v3d_bo(obj);
>  
> -	v3d_mmu_remove_ptes(bo);
> +	if (drm_mm_node_allocated(&bo->node)) {
> +		v3d_mmu_remove_ptes(bo);
>  
> -	mutex_lock(&v3d->bo_lock);
> -	v3d->bo_stats.num_allocated--;
> -	v3d->bo_stats.pages_allocated -= obj->size >> PAGE_SHIFT;
> -	mutex_unlock(&v3d->bo_lock);
> +		mutex_lock(&v3d->bo_lock);
> +		v3d->bo_stats.num_allocated--;
> +		v3d->bo_stats.pages_allocated -= obj->size >> PAGE_SHIFT;
> +		mutex_unlock(&v3d->bo_lock);
>  
> -	spin_lock(&v3d->mm_lock);
> -	drm_mm_remove_node(&bo->node);
> -	spin_unlock(&v3d->mm_lock);
> +		spin_lock(&v3d->mm_lock);
> +		drm_mm_remove_node(&bo->node);
> +		spin_unlock(&v3d->mm_lock);
> +	}
>  
>  	/* GPU execution may have dirtied any pages in the BO. */
>  	bo->base.pages_mark_dirty_on_put = true;
> @@ -142,7 +144,7 @@ struct v3d_bo *v3d_bo_create(struct drm_device *dev, struct drm_file *file_priv,
>  	return bo;
>  
>  free_obj:
> -	drm_gem_shmem_free(shmem_obj);
> +	drm_gem_object_put(&shmem_obj->base);
>  	return ERR_PTR(ret);
>  }
>  
> @@ -160,7 +162,7 @@ v3d_prime_import_sg_table(struct drm_device *dev,
>  
>  	ret = v3d_bo_create_finish(obj);
>  	if (ret) {
> -		drm_gem_shmem_free(&to_v3d_bo(obj)->base);
> +		drm_gem_object_put(obj);
>  		return ERR_PTR(ret);
>  	}
>  

[PATCH v16 06/20] drm/virtio: Replace drm_gem_shmem_free() with drm_gem_object_put()

[Dmitry Osipenko]

Prepare virtio_gpu_object_create() to addition of memory shrinker support
by replacing open-coded drm_gem_shmem_free() with drm_gem_object_put() that
decrements GEM refcount to 0, which becomes important for drm-shmem because
it will start to use GEM's refcount during the shmem's BO freeing time in
order to prevent spurious lockdep warning about resv lock ordering vs
fs_reclaim code paths.

Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/virtio/virtgpu_object.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c
index c7e74cf13022..343b13428125 100644
--- a/drivers/gpu/drm/virtio/virtgpu_object.c
+++ b/drivers/gpu/drm/virtio/virtgpu_object.c
@@ -244,6 +244,6 @@ int virtio_gpu_object_create(struct virtio_gpu_device *vgdev,
 err_put_id:
 	virtio_gpu_resource_id_put(vgdev, bo->hw_res_handle);
 err_free_gem:
-	drm_gem_shmem_free(shmem_obj);
+	drm_gem_object_put(&bo->base.base);
 	return ret;
 }
-- 
2.41.0

Re: [PATCH v16 06/20] drm/virtio: Replace drm_gem_shmem_free() with drm_gem_object_put()

[Boris Brezillon]

On Sun,  3 Sep 2023 20:07:22 +0300
Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:

> Prepare virtio_gpu_object_create() to addition of memory shrinker support
> by replacing open-coded drm_gem_shmem_free() with drm_gem_object_put() that
> decrements GEM refcount to 0, which becomes important for drm-shmem because
> it will start to use GEM's refcount during the shmem's BO freeing time in
> order to prevent spurious lockdep warning about resv lock ordering vs
> fs_reclaim code paths.

I think I'm okay with the change (assuming virtio_gpu_free_object()
can deal with partially initialized objects), not with the explanation
:-). I don't really see why we need to take the resv lock in
drm_gem_shmem_free(). As said in my v15 review, I think we should
replace the drm_gem_shmem_put_pages() call we have in
drm_gem_shmem_free() by a call to a new drm_gem_shmem_free_pages()
helper that does exactly what drm_gem_shmem_put_pages() does without
the refcounting/locking, because all that should remain at the time
drm_gem_shmem_free() is called is the implicit pages ref owned by
shmem->sgt, and there's no risk of other threads accessing the GEM
object at that point.

> 
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> ---
>  drivers/gpu/drm/virtio/virtgpu_object.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c
> index c7e74cf13022..343b13428125 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_object.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_object.c
> @@ -244,6 +244,6 @@ int virtio_gpu_object_create(struct virtio_gpu_device *vgdev,
>  err_put_id:
>  	virtio_gpu_resource_id_put(vgdev, bo->hw_res_handle);
>  err_free_gem:
> -	drm_gem_shmem_free(shmem_obj);
> +	drm_gem_object_put(&bo->base.base);
>  	return ret;
>  }

Re: [PATCH v16 06/20] drm/virtio: Replace drm_gem_shmem_free() with drm_gem_object_put()

[Dmitry Osipenko]

On 9/5/23 10:20, Boris Brezillon wrote:
> On Sun,  3 Sep 2023 20:07:22 +0300
> Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
> 
>> Prepare virtio_gpu_object_create() to addition of memory shrinker support
>> by replacing open-coded drm_gem_shmem_free() with drm_gem_object_put() that
>> decrements GEM refcount to 0, which becomes important for drm-shmem because
>> it will start to use GEM's refcount during the shmem's BO freeing time in
>> order to prevent spurious lockdep warning about resv lock ordering vs
>> fs_reclaim code paths.
> 
> I think I'm okay with the change (assuming virtio_gpu_free_object()
> can deal with partially initialized objects), not with the explanation
> :-). I don't really see why we need to take the resv lock in
> drm_gem_shmem_free(). As said in my v15 review, I think we should
> replace the drm_gem_shmem_put_pages() call we have in
> drm_gem_shmem_free() by a call to a new drm_gem_shmem_free_pages()
> helper that does exactly what drm_gem_shmem_put_pages() does without
> the refcounting/locking, because all that should remain at the time
> drm_gem_shmem_free() is called is the implicit pages ref owned by
> shmem->sgt, and there's no risk of other threads accessing the GEM
> object at that point.

Apparently I forgot to drop these drm_gem_object_put() patches by
accident in v16, the drm_gem_shmem_free() doesn't touch resv lock
anymore. Will re-check for v17.

-- 
Best regards,
Dmitry

[PATCH v16 07/20] drm/shmem-helper: Make all exported symbols GPL

[Dmitry Osipenko]

Make all drm-shmem exported symbols GPL to make them consistent with
the rest of drm-shmem symbols.

Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 848435e08eb2..5c777adf1bcb 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -228,7 +228,7 @@ void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem)
 			  shmem->pages_mark_accessed_on_put);
 	shmem->pages = NULL;
 }
-EXPORT_SYMBOL(drm_gem_shmem_put_pages);
+EXPORT_SYMBOL_GPL(drm_gem_shmem_put_pages);
 
 static int drm_gem_shmem_pin_locked(struct drm_gem_shmem_object *shmem)
 {
@@ -273,7 +273,7 @@ int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem)
 
 	return ret;
 }
-EXPORT_SYMBOL(drm_gem_shmem_pin);
+EXPORT_SYMBOL_GPL(drm_gem_shmem_pin);
 
 /**
  * drm_gem_shmem_unpin - Unpin backing pages for a shmem GEM object
@@ -292,7 +292,7 @@ void drm_gem_shmem_unpin(struct drm_gem_shmem_object *shmem)
 	drm_gem_shmem_unpin_locked(shmem);
 	dma_resv_unlock(shmem->base.resv);
 }
-EXPORT_SYMBOL(drm_gem_shmem_unpin);
+EXPORT_SYMBOL_GPL(drm_gem_shmem_unpin);
 
 /*
  * drm_gem_shmem_vmap - Create a virtual mapping for a shmem GEM object
@@ -362,7 +362,7 @@ int drm_gem_shmem_vmap(struct drm_gem_shmem_object *shmem,
 
 	return ret;
 }
-EXPORT_SYMBOL(drm_gem_shmem_vmap);
+EXPORT_SYMBOL_GPL(drm_gem_shmem_vmap);
 
 /*
  * drm_gem_shmem_vunmap - Unmap a virtual mapping for a shmem GEM object
@@ -398,7 +398,7 @@ void drm_gem_shmem_vunmap(struct drm_gem_shmem_object *shmem,
 
 	shmem->vaddr = NULL;
 }
-EXPORT_SYMBOL(drm_gem_shmem_vunmap);
+EXPORT_SYMBOL_GPL(drm_gem_shmem_vunmap);
 
 static int
 drm_gem_shmem_create_with_handle(struct drm_file *file_priv,
@@ -437,7 +437,7 @@ int drm_gem_shmem_madvise(struct drm_gem_shmem_object *shmem, int madv)
 
 	return (madv >= 0);
 }
-EXPORT_SYMBOL(drm_gem_shmem_madvise);
+EXPORT_SYMBOL_GPL(drm_gem_shmem_madvise);
 
 void drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem)
 {
@@ -469,7 +469,7 @@ void drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem)
 
 	invalidate_mapping_pages(file_inode(obj->filp)->i_mapping, 0, (loff_t)-1);
 }
-EXPORT_SYMBOL(drm_gem_shmem_purge);
+EXPORT_SYMBOL_GPL(drm_gem_shmem_purge);
 
 /**
  * drm_gem_shmem_dumb_create - Create a dumb shmem buffer object
@@ -644,7 +644,7 @@ void drm_gem_shmem_print_info(const struct drm_gem_shmem_object *shmem,
 	drm_printf_indent(p, indent, "vmap_use_count=%u\n", shmem->vmap_use_count);
 	drm_printf_indent(p, indent, "vaddr=%p\n", shmem->vaddr);
 }
-EXPORT_SYMBOL(drm_gem_shmem_print_info);
+EXPORT_SYMBOL_GPL(drm_gem_shmem_print_info);
 
 /**
  * drm_gem_shmem_get_sg_table - Provide a scatter/gather table of pinned
-- 
2.41.0

Re: [PATCH v16 07/20] drm/shmem-helper: Make all exported symbols GPL

[Boris Brezillon]

On Sun,  3 Sep 2023 20:07:23 +0300
Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:

> Make all drm-shmem exported symbols GPL to make them consistent with
> the rest of drm-shmem symbols.
> 
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>

> ---
>  drivers/gpu/drm/drm_gem_shmem_helper.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index 848435e08eb2..5c777adf1bcb 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -228,7 +228,7 @@ void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem)
>  			  shmem->pages_mark_accessed_on_put);
>  	shmem->pages = NULL;
>  }
> -EXPORT_SYMBOL(drm_gem_shmem_put_pages);
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_put_pages);
>  
>  static int drm_gem_shmem_pin_locked(struct drm_gem_shmem_object *shmem)
>  {
> @@ -273,7 +273,7 @@ int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem)
>  
>  	return ret;
>  }
> -EXPORT_SYMBOL(drm_gem_shmem_pin);
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_pin);
>  
>  /**
>   * drm_gem_shmem_unpin - Unpin backing pages for a shmem GEM object
> @@ -292,7 +292,7 @@ void drm_gem_shmem_unpin(struct drm_gem_shmem_object *shmem)
>  	drm_gem_shmem_unpin_locked(shmem);
>  	dma_resv_unlock(shmem->base.resv);
>  }
> -EXPORT_SYMBOL(drm_gem_shmem_unpin);
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_unpin);
>  
>  /*
>   * drm_gem_shmem_vmap - Create a virtual mapping for a shmem GEM object
> @@ -362,7 +362,7 @@ int drm_gem_shmem_vmap(struct drm_gem_shmem_object *shmem,
>  
>  	return ret;
>  }
> -EXPORT_SYMBOL(drm_gem_shmem_vmap);
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_vmap);
>  
>  /*
>   * drm_gem_shmem_vunmap - Unmap a virtual mapping for a shmem GEM object
> @@ -398,7 +398,7 @@ void drm_gem_shmem_vunmap(struct drm_gem_shmem_object *shmem,
>  
>  	shmem->vaddr = NULL;
>  }
> -EXPORT_SYMBOL(drm_gem_shmem_vunmap);
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_vunmap);
>  
>  static int
>  drm_gem_shmem_create_with_handle(struct drm_file *file_priv,
> @@ -437,7 +437,7 @@ int drm_gem_shmem_madvise(struct drm_gem_shmem_object *shmem, int madv)
>  
>  	return (madv >= 0);
>  }
> -EXPORT_SYMBOL(drm_gem_shmem_madvise);
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_madvise);
>  
>  void drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem)
>  {
> @@ -469,7 +469,7 @@ void drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem)
>  
>  	invalidate_mapping_pages(file_inode(obj->filp)->i_mapping, 0, (loff_t)-1);
>  }
> -EXPORT_SYMBOL(drm_gem_shmem_purge);
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_purge);
>  
>  /**
>   * drm_gem_shmem_dumb_create - Create a dumb shmem buffer object
> @@ -644,7 +644,7 @@ void drm_gem_shmem_print_info(const struct drm_gem_shmem_object *shmem,
>  	drm_printf_indent(p, indent, "vmap_use_count=%u\n", shmem->vmap_use_count);
>  	drm_printf_indent(p, indent, "vaddr=%p\n", shmem->vaddr);
>  }
> -EXPORT_SYMBOL(drm_gem_shmem_print_info);
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_print_info);
>  
>  /**
>   * drm_gem_shmem_get_sg_table - Provide a scatter/gather table of pinned

[PATCH v16 08/20] drm/shmem-helper: Refactor locked/unlocked functions

[Dmitry Osipenko]

Add locked and remove unlocked postfixes from drm-shmem function names,
making names consistent with the drm/gem core code.

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c        | 64 +++++++++----------
 drivers/gpu/drm/lima/lima_gem.c               |  8 +--
 drivers/gpu/drm/panfrost/panfrost_drv.c       |  2 +-
 drivers/gpu/drm/panfrost/panfrost_gem.c       |  6 +-
 .../gpu/drm/panfrost/panfrost_gem_shrinker.c  |  2 +-
 drivers/gpu/drm/panfrost/panfrost_mmu.c       |  2 +-
 drivers/gpu/drm/v3d/v3d_bo.c                  |  4 +-
 drivers/gpu/drm/virtio/virtgpu_object.c       |  4 +-
 include/drm/drm_gem_shmem_helper.h            | 36 +++++------
 9 files changed, 64 insertions(+), 64 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 5c777adf1bcb..2b50d1a7f718 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -43,8 +43,8 @@ static const struct drm_gem_object_funcs drm_gem_shmem_funcs = {
 	.pin = drm_gem_shmem_object_pin,
 	.unpin = drm_gem_shmem_object_unpin,
 	.get_sg_table = drm_gem_shmem_object_get_sg_table,
-	.vmap = drm_gem_shmem_object_vmap,
-	.vunmap = drm_gem_shmem_object_vunmap,
+	.vmap = drm_gem_shmem_object_vmap_locked,
+	.vunmap = drm_gem_shmem_object_vunmap_locked,
 	.mmap = drm_gem_shmem_object_mmap,
 	.vm_ops = &drm_gem_shmem_vm_ops,
 };
@@ -153,7 +153,7 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
 			kfree(shmem->sgt);
 		}
 		if (shmem->pages) {
-			drm_gem_shmem_put_pages(shmem);
+			drm_gem_shmem_put_pages_locked(shmem);
 			drm_WARN_ON(obj->dev, !shmem->got_pages_sgt);
 		}
 
@@ -167,7 +167,7 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_free);
 
-static int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem)
+static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
 {
 	struct drm_gem_object *obj = &shmem->base;
 	struct page **pages;
@@ -201,12 +201,12 @@ static int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem)
 }
 
 /*
- * drm_gem_shmem_put_pages - Decrease use count on the backing pages for a shmem GEM object
+ * drm_gem_shmem_put_pages_locked - Decrease use count on the backing pages for a shmem GEM object
  * @shmem: shmem GEM object
  *
  * This function decreases the use count and puts the backing pages when use drops to zero.
  */
-void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem)
+void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
 {
 	struct drm_gem_object *obj = &shmem->base;
 
@@ -228,7 +228,7 @@ void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem)
 			  shmem->pages_mark_accessed_on_put);
 	shmem->pages = NULL;
 }
-EXPORT_SYMBOL_GPL(drm_gem_shmem_put_pages);
+EXPORT_SYMBOL_GPL(drm_gem_shmem_put_pages_locked);
 
 static int drm_gem_shmem_pin_locked(struct drm_gem_shmem_object *shmem)
 {
@@ -236,7 +236,7 @@ static int drm_gem_shmem_pin_locked(struct drm_gem_shmem_object *shmem)
 
 	dma_resv_assert_held(shmem->base.resv);
 
-	ret = drm_gem_shmem_get_pages(shmem);
+	ret = drm_gem_shmem_get_pages_locked(shmem);
 
 	return ret;
 }
@@ -245,7 +245,7 @@ static void drm_gem_shmem_unpin_locked(struct drm_gem_shmem_object *shmem)
 {
 	dma_resv_assert_held(shmem->base.resv);
 
-	drm_gem_shmem_put_pages(shmem);
+	drm_gem_shmem_put_pages_locked(shmem);
 }
 
 /**
@@ -295,7 +295,7 @@ void drm_gem_shmem_unpin(struct drm_gem_shmem_object *shmem)
 EXPORT_SYMBOL_GPL(drm_gem_shmem_unpin);
 
 /*
- * drm_gem_shmem_vmap - Create a virtual mapping for a shmem GEM object
+ * drm_gem_shmem_vmap_locked - Create a virtual mapping for a shmem GEM object
  * @shmem: shmem GEM object
  * @map: Returns the kernel virtual address of the SHMEM GEM object's backing
  *       store.
@@ -304,13 +304,13 @@ EXPORT_SYMBOL_GPL(drm_gem_shmem_unpin);
  * exists for the buffer backing the shmem GEM object. It hides the differences
  * between dma-buf imported and natively allocated objects.
  *
- * Acquired mappings should be cleaned up by calling drm_gem_shmem_vunmap().
+ * Acquired mappings should be cleaned up by calling drm_gem_shmem_vunmap_locked().
  *
  * Returns:
  * 0 on success or a negative error code on failure.
  */
-int drm_gem_shmem_vmap(struct drm_gem_shmem_object *shmem,
-		       struct iosys_map *map)
+int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem,
+			      struct iosys_map *map)
 {
 	struct drm_gem_object *obj = &shmem->base;
 	int ret = 0;
@@ -333,7 +333,7 @@ int drm_gem_shmem_vmap(struct drm_gem_shmem_object *shmem,
 			return 0;
 		}
 
-		ret = drm_gem_shmem_get_pages(shmem);
+		ret = drm_gem_shmem_get_pages_locked(shmem);
 		if (ret)
 			goto err_zero_use;
 
@@ -356,28 +356,28 @@ int drm_gem_shmem_vmap(struct drm_gem_shmem_object *shmem,
 
 err_put_pages:
 	if (!obj->import_attach)
-		drm_gem_shmem_put_pages(shmem);
+		drm_gem_shmem_put_pages_locked(shmem);
 err_zero_use:
 	shmem->vmap_use_count = 0;
 
 	return ret;
 }
-EXPORT_SYMBOL_GPL(drm_gem_shmem_vmap);
+EXPORT_SYMBOL_GPL(drm_gem_shmem_vmap_locked);
 
 /*
- * drm_gem_shmem_vunmap - Unmap a virtual mapping for a shmem GEM object
+ * drm_gem_shmem_vunmap_locked - Unmap a virtual mapping for a shmem GEM object
  * @shmem: shmem GEM object
  * @map: Kernel virtual address where the SHMEM GEM object was mapped
  *
  * This function cleans up a kernel virtual address mapping acquired by
- * drm_gem_shmem_vmap(). The mapping is only removed when the use count drops to
- * zero.
+ * drm_gem_shmem_vmap_locked(). The mapping is only removed when the use count
+ * drops to zero.
  *
  * This function hides the differences between dma-buf imported and natively
  * allocated objects.
  */
-void drm_gem_shmem_vunmap(struct drm_gem_shmem_object *shmem,
-			  struct iosys_map *map)
+void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem,
+				 struct iosys_map *map)
 {
 	struct drm_gem_object *obj = &shmem->base;
 
@@ -393,12 +393,12 @@ void drm_gem_shmem_vunmap(struct drm_gem_shmem_object *shmem,
 			return;
 
 		vunmap(shmem->vaddr);
-		drm_gem_shmem_put_pages(shmem);
+		drm_gem_shmem_put_pages_locked(shmem);
 	}
 
 	shmem->vaddr = NULL;
 }
-EXPORT_SYMBOL_GPL(drm_gem_shmem_vunmap);
+EXPORT_SYMBOL_GPL(drm_gem_shmem_vunmap_locked);
 
 static int
 drm_gem_shmem_create_with_handle(struct drm_file *file_priv,
@@ -426,7 +426,7 @@ drm_gem_shmem_create_with_handle(struct drm_file *file_priv,
 /* Update madvise status, returns true if not purged, else
  * false or -errno.
  */
-int drm_gem_shmem_madvise(struct drm_gem_shmem_object *shmem, int madv)
+int drm_gem_shmem_madvise_locked(struct drm_gem_shmem_object *shmem, int madv)
 {
 	dma_resv_assert_held(shmem->base.resv);
 
@@ -437,9 +437,9 @@ int drm_gem_shmem_madvise(struct drm_gem_shmem_object *shmem, int madv)
 
 	return (madv >= 0);
 }
-EXPORT_SYMBOL_GPL(drm_gem_shmem_madvise);
+EXPORT_SYMBOL_GPL(drm_gem_shmem_madvise_locked);
 
-void drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem)
+void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem)
 {
 	struct drm_gem_object *obj = &shmem->base;
 	struct drm_device *dev = obj->dev;
@@ -453,7 +453,7 @@ void drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem)
 	kfree(shmem->sgt);
 	shmem->sgt = NULL;
 
-	drm_gem_shmem_put_pages(shmem);
+	drm_gem_shmem_put_pages_locked(shmem);
 
 	shmem->madv = -1;
 
@@ -469,7 +469,7 @@ void drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem)
 
 	invalidate_mapping_pages(file_inode(obj->filp)->i_mapping, 0, (loff_t)-1);
 }
-EXPORT_SYMBOL_GPL(drm_gem_shmem_purge);
+EXPORT_SYMBOL_GPL(drm_gem_shmem_purge_locked);
 
 /**
  * drm_gem_shmem_dumb_create - Create a dumb shmem buffer object
@@ -566,7 +566,7 @@ static void drm_gem_shmem_vm_close(struct vm_area_struct *vma)
 	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
 
 	dma_resv_lock(shmem->base.resv, NULL);
-	drm_gem_shmem_put_pages(shmem);
+	drm_gem_shmem_put_pages_locked(shmem);
 	dma_resv_unlock(shmem->base.resv);
 
 	drm_gem_vm_close(vma);
@@ -613,7 +613,7 @@ int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct
 	}
 
 	dma_resv_lock(shmem->base.resv, NULL);
-	ret = drm_gem_shmem_get_pages(shmem);
+	ret = drm_gem_shmem_get_pages_locked(shmem);
 	dma_resv_unlock(shmem->base.resv);
 
 	if (ret)
@@ -681,7 +681,7 @@ static struct sg_table *drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_
 
 	drm_WARN_ON(obj->dev, obj->import_attach);
 
-	ret = drm_gem_shmem_get_pages(shmem);
+	ret = drm_gem_shmem_get_pages_locked(shmem);
 	if (ret)
 		return ERR_PTR(ret);
 
@@ -710,7 +710,7 @@ static struct sg_table *drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_
 	sg_free_table(sgt);
 	kfree(sgt);
 err_put_pages:
-	drm_gem_shmem_put_pages(shmem);
+	drm_gem_shmem_put_pages_locked(shmem);
 	return ERR_PTR(ret);
 }
 
diff --git a/drivers/gpu/drm/lima/lima_gem.c b/drivers/gpu/drm/lima/lima_gem.c
index 67c39b95e30e..ec8f718aa539 100644
--- a/drivers/gpu/drm/lima/lima_gem.c
+++ b/drivers/gpu/drm/lima/lima_gem.c
@@ -181,7 +181,7 @@ static int lima_gem_pin(struct drm_gem_object *obj)
 	if (bo->heap_size)
 		return -EINVAL;
 
-	return drm_gem_shmem_pin(&bo->base);
+	return drm_gem_shmem_object_pin(obj);
 }
 
 static int lima_gem_vmap(struct drm_gem_object *obj, struct iosys_map *map)
@@ -191,7 +191,7 @@ static int lima_gem_vmap(struct drm_gem_object *obj, struct iosys_map *map)
 	if (bo->heap_size)
 		return -EINVAL;
 
-	return drm_gem_shmem_vmap(&bo->base, map);
+	return drm_gem_shmem_object_vmap_locked(obj, map);
 }
 
 static int lima_gem_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
@@ -201,7 +201,7 @@ static int lima_gem_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
 	if (bo->heap_size)
 		return -EINVAL;
 
-	return drm_gem_shmem_mmap(&bo->base, vma);
+	return drm_gem_shmem_object_mmap(obj, vma);
 }
 
 static const struct drm_gem_object_funcs lima_gem_funcs = {
@@ -213,7 +213,7 @@ static const struct drm_gem_object_funcs lima_gem_funcs = {
 	.unpin = drm_gem_shmem_object_unpin,
 	.get_sg_table = drm_gem_shmem_object_get_sg_table,
 	.vmap = lima_gem_vmap,
-	.vunmap = drm_gem_shmem_object_vunmap,
+	.vunmap = drm_gem_shmem_object_vunmap_locked,
 	.mmap = lima_gem_mmap,
 	.vm_ops = &drm_gem_shmem_vm_ops,
 };
diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
index a2ab99698ca8..175443eacead 100644
--- a/drivers/gpu/drm/panfrost/panfrost_drv.c
+++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
@@ -436,7 +436,7 @@ static int panfrost_ioctl_madvise(struct drm_device *dev, void *data,
 		}
 	}
 
-	args->retained = drm_gem_shmem_madvise(&bo->base, args->madv);
+	args->retained = drm_gem_shmem_madvise_locked(&bo->base, args->madv);
 
 	if (args->retained) {
 		if (args->madv == PANFROST_MADV_DONTNEED)
diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
index 3c812fbd126f..59c8c73c6a59 100644
--- a/drivers/gpu/drm/panfrost/panfrost_gem.c
+++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
@@ -192,7 +192,7 @@ static int panfrost_gem_pin(struct drm_gem_object *obj)
 	if (bo->is_heap)
 		return -EINVAL;
 
-	return drm_gem_shmem_pin(&bo->base);
+	return drm_gem_shmem_object_pin(obj);
 }
 
 static const struct drm_gem_object_funcs panfrost_gem_funcs = {
@@ -203,8 +203,8 @@ static const struct drm_gem_object_funcs panfrost_gem_funcs = {
 	.pin = panfrost_gem_pin,
 	.unpin = drm_gem_shmem_object_unpin,
 	.get_sg_table = drm_gem_shmem_object_get_sg_table,
-	.vmap = drm_gem_shmem_object_vmap,
-	.vunmap = drm_gem_shmem_object_vunmap,
+	.vmap = drm_gem_shmem_object_vmap_locked,
+	.vunmap = drm_gem_shmem_object_vunmap_locked,
 	.mmap = drm_gem_shmem_object_mmap,
 	.vm_ops = &drm_gem_shmem_vm_ops,
 };
diff --git a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
index 6a71a2555f85..72193bd734e1 100644
--- a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
+++ b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
@@ -52,7 +52,7 @@ static bool panfrost_gem_purge(struct drm_gem_object *obj)
 		goto unlock_mappings;
 
 	panfrost_gem_teardown_mappings_locked(bo);
-	drm_gem_shmem_purge(&bo->base);
+	drm_gem_shmem_purge_locked(&bo->base);
 	ret = true;
 
 	dma_resv_unlock(shmem->base.resv);
diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
index c0123d09f699..7771769f0ce0 100644
--- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
+++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
@@ -535,7 +535,7 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
 err_map:
 	sg_free_table(sgt);
 err_pages:
-	drm_gem_shmem_put_pages(&bo->base);
+	drm_gem_shmem_put_pages_locked(&bo->base);
 err_unlock:
 	dma_resv_unlock(obj->resv);
 err_bo:
diff --git a/drivers/gpu/drm/v3d/v3d_bo.c b/drivers/gpu/drm/v3d/v3d_bo.c
index 70c1095d6eec..6a0e7b6177d5 100644
--- a/drivers/gpu/drm/v3d/v3d_bo.c
+++ b/drivers/gpu/drm/v3d/v3d_bo.c
@@ -58,8 +58,8 @@ static const struct drm_gem_object_funcs v3d_gem_funcs = {
 	.pin = drm_gem_shmem_object_pin,
 	.unpin = drm_gem_shmem_object_unpin,
 	.get_sg_table = drm_gem_shmem_object_get_sg_table,
-	.vmap = drm_gem_shmem_object_vmap,
-	.vunmap = drm_gem_shmem_object_vunmap,
+	.vmap = drm_gem_shmem_object_vmap_locked,
+	.vunmap = drm_gem_shmem_object_vunmap_locked,
 	.mmap = drm_gem_shmem_object_mmap,
 	.vm_ops = &drm_gem_shmem_vm_ops,
 };
diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c
index 343b13428125..97020ed56b81 100644
--- a/drivers/gpu/drm/virtio/virtgpu_object.c
+++ b/drivers/gpu/drm/virtio/virtgpu_object.c
@@ -106,8 +106,8 @@ static const struct drm_gem_object_funcs virtio_gpu_shmem_funcs = {
 	.pin = drm_gem_shmem_object_pin,
 	.unpin = drm_gem_shmem_object_unpin,
 	.get_sg_table = drm_gem_shmem_object_get_sg_table,
-	.vmap = drm_gem_shmem_object_vmap,
-	.vunmap = drm_gem_shmem_object_vunmap,
+	.vmap = drm_gem_shmem_object_vmap_locked,
+	.vunmap = drm_gem_shmem_object_vunmap_locked,
 	.mmap = drm_gem_shmem_object_mmap,
 	.vm_ops = &drm_gem_shmem_vm_ops,
 };
diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
index a53c0874b3c4..808083279fd5 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -113,16 +113,16 @@ struct drm_gem_shmem_object {
 struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t size);
 void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem);
 
-void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem);
+void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem);
 int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem);
 void drm_gem_shmem_unpin(struct drm_gem_shmem_object *shmem);
-int drm_gem_shmem_vmap(struct drm_gem_shmem_object *shmem,
-		       struct iosys_map *map);
-void drm_gem_shmem_vunmap(struct drm_gem_shmem_object *shmem,
-			  struct iosys_map *map);
+int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem,
+			      struct iosys_map *map);
+void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem,
+				 struct iosys_map *map);
 int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct *vma);
 
-int drm_gem_shmem_madvise(struct drm_gem_shmem_object *shmem, int madv);
+int drm_gem_shmem_madvise_locked(struct drm_gem_shmem_object *shmem, int madv);
 
 static inline bool drm_gem_shmem_is_purgeable(struct drm_gem_shmem_object *shmem)
 {
@@ -131,7 +131,7 @@ static inline bool drm_gem_shmem_is_purgeable(struct drm_gem_shmem_object *shmem
 		!shmem->base.dma_buf && !shmem->base.import_attach;
 }
 
-void drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem);
+void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem);
 
 struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_shmem_object *shmem);
 struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_shmem_object *shmem);
@@ -222,22 +222,22 @@ static inline struct sg_table *drm_gem_shmem_object_get_sg_table(struct drm_gem_
 }
 
 /*
- * drm_gem_shmem_object_vmap - GEM object function for drm_gem_shmem_vmap()
+ * drm_gem_shmem_object_vmap_locked - GEM object function for drm_gem_shmem_vmap_locked()
  * @obj: GEM object
  * @map: Returns the kernel virtual address of the SHMEM GEM object's backing store.
  *
- * This function wraps drm_gem_shmem_vmap(). Drivers that employ the shmem helpers should
- * use it as their &drm_gem_object_funcs.vmap handler.
+ * This function wraps drm_gem_shmem_vmap_locked(). Drivers that employ the shmem
+ * helpers should use it as their &drm_gem_object_funcs.vmap handler.
  *
  * Returns:
  * 0 on success or a negative error code on failure.
  */
-static inline int drm_gem_shmem_object_vmap(struct drm_gem_object *obj,
-					    struct iosys_map *map)
+static inline int drm_gem_shmem_object_vmap_locked(struct drm_gem_object *obj,
+						   struct iosys_map *map)
 {
 	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
 
-	return drm_gem_shmem_vmap(shmem, map);
+	return drm_gem_shmem_vmap_locked(shmem, map);
 }
 
 /*
@@ -245,15 +245,15 @@ static inline int drm_gem_shmem_object_vmap(struct drm_gem_object *obj,
  * @obj: GEM object
  * @map: Kernel virtual address where the SHMEM GEM object was mapped
  *
- * This function wraps drm_gem_shmem_vunmap(). Drivers that employ the shmem helpers should
- * use it as their &drm_gem_object_funcs.vunmap handler.
+ * This function wraps drm_gem_shmem_vunmap_locked(). Drivers that employ the shmem
+ * helpers should use it as their &drm_gem_object_funcs.vunmap handler.
  */
-static inline void drm_gem_shmem_object_vunmap(struct drm_gem_object *obj,
-					       struct iosys_map *map)
+static inline void drm_gem_shmem_object_vunmap_locked(struct drm_gem_object *obj,
+						      struct iosys_map *map)
 {
 	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
 
-	drm_gem_shmem_vunmap(shmem, map);
+	drm_gem_shmem_vunmap_locked(shmem, map);
 }
 
 /**
-- 
2.41.0

[PATCH v16 09/20] drm/shmem-helper: Remove obsoleted is_iomem test

[Dmitry Osipenko]

Everything that uses the mapped buffer should be agnostic to is_iomem.
The only reason for the is_iomem test is that we're setting shmem->vaddr
to the returned map->vaddr. Now that the shmem->vaddr code is gone, remove
the obsoleted is_iomem test to clean up the code.

Suggested-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 2b50d1a7f718..25e99468ced2 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -317,12 +317,6 @@ int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem,
 
 	if (obj->import_attach) {
 		ret = dma_buf_vmap(obj->import_attach->dmabuf, map);
-		if (!ret) {
-			if (drm_WARN_ON(obj->dev, map->is_iomem)) {
-				dma_buf_vunmap(obj->import_attach->dmabuf, map);
-				return -EIO;
-			}
-		}
 	} else {
 		pgprot_t prot = PAGE_KERNEL;
 
-- 
2.41.0

Re: [PATCH v16 09/20] drm/shmem-helper: Remove obsoleted is_iomem test

[Boris Brezillon]

On Sun,  3 Sep 2023 20:07:25 +0300
Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:

> Everything that uses the mapped buffer should be agnostic to is_iomem.
> The only reason for the is_iomem test is that we're setting shmem->vaddr
> to the returned map->vaddr. Now that the shmem->vaddr code is gone, remove
> the obsoleted is_iomem test to clean up the code.
> 
> Suggested-by: Thomas Zimmermann <tzimmermann@suse.de>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> ---
>  drivers/gpu/drm/drm_gem_shmem_helper.c | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index 2b50d1a7f718..25e99468ced2 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -317,12 +317,6 @@ int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem,
>  
>  	if (obj->import_attach) {
>  		ret = dma_buf_vmap(obj->import_attach->dmabuf, map);
> -		if (!ret) {
> -			if (drm_WARN_ON(obj->dev, map->is_iomem)) {
> -				dma_buf_vunmap(obj->import_attach->dmabuf, map);
> -				return -EIO;
> -			}
> -		}

Given there's nothing to unroll for the dmabuf case, I think it'd be
good to return directly and skip all the error paths. It would also
allow you to get rid of one indentation level for the !dmabuf path.

	if (obj->import_attach)
		return dma_buf_vmap(obj->import_attach->dmabuf, map);

	// non-dmabuf vmap logic here...



>  	} else {
>  		pgprot_t prot = PAGE_KERNEL;
>  

Re: [PATCH v16 09/20] drm/shmem-helper: Remove obsoleted is_iomem test

[Dmitry Osipenko]

On 9/5/23 09:46, Boris Brezillon wrote:
> On Sun,  3 Sep 2023 20:07:25 +0300
> Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
> 
>> Everything that uses the mapped buffer should be agnostic to is_iomem.
>> The only reason for the is_iomem test is that we're setting shmem->vaddr
>> to the returned map->vaddr. Now that the shmem->vaddr code is gone, remove
>> the obsoleted is_iomem test to clean up the code.
>>
>> Suggested-by: Thomas Zimmermann <tzimmermann@suse.de>
>> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
>> ---
>>  drivers/gpu/drm/drm_gem_shmem_helper.c | 6 ------
>>  1 file changed, 6 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
>> index 2b50d1a7f718..25e99468ced2 100644
>> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
>> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
>> @@ -317,12 +317,6 @@ int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem,
>>  
>>  	if (obj->import_attach) {
>>  		ret = dma_buf_vmap(obj->import_attach->dmabuf, map);
>> -		if (!ret) {
>> -			if (drm_WARN_ON(obj->dev, map->is_iomem)) {
>> -				dma_buf_vunmap(obj->import_attach->dmabuf, map);
>> -				return -EIO;
>> -			}
>> -		}
> 
> Given there's nothing to unroll for the dmabuf case, I think it'd be
> good to return directly and skip all the error paths. It would also
> allow you to get rid of one indentation level for the !dmabuf path.
> 
> 	if (obj->import_attach)
> 		return dma_buf_vmap(obj->import_attach->dmabuf, map);
> 
> 	// non-dmabuf vmap logic here...

There is a common error message there that uses the common ret. The
error unwinding could be improved, but then it should be a separate
patch as it's unrelated to the change made here.

-- 
Best regards,
Dmitry

[PATCH v16 10/20] drm/shmem-helper: Add and use pages_pin_count

[Dmitry Osipenko]

Add separate pages_pin_count for tracking of whether drm-shmem pages are
moveable or not. With the addition of memory shrinker support to drm-shmem,
the pages_use_count will no longer determine whether pages are hard-pinned
in memory, but whether pages exist and are soft-pinned (and could be swapped
out). The pages_pin_count > 1 will hard-pin pages in memory.

Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 24 ++++++++++++++++--------
 include/drm/drm_gem_shmem_helper.h     | 10 ++++++++++
 2 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 25e99468ced2..7e1e674e2c9f 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -236,18 +236,16 @@ static int drm_gem_shmem_pin_locked(struct drm_gem_shmem_object *shmem)
 
 	dma_resv_assert_held(shmem->base.resv);
 
+	if (refcount_inc_not_zero(&shmem->pages_pin_count))
+		return 0;
+
 	ret = drm_gem_shmem_get_pages_locked(shmem);
+	if (!ret)
+		refcount_set(&shmem->pages_pin_count, 1);
 
 	return ret;
 }
 
-static void drm_gem_shmem_unpin_locked(struct drm_gem_shmem_object *shmem)
-{
-	dma_resv_assert_held(shmem->base.resv);
-
-	drm_gem_shmem_put_pages_locked(shmem);
-}
-
 /**
  * drm_gem_shmem_pin - Pin backing pages for a shmem GEM object
  * @shmem: shmem GEM object
@@ -265,6 +263,9 @@ int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem)
 
 	drm_WARN_ON(obj->dev, obj->import_attach);
 
+	if (refcount_inc_not_zero(&shmem->pages_pin_count))
+		return 0;
+
 	ret = dma_resv_lock_interruptible(shmem->base.resv, NULL);
 	if (ret)
 		return ret;
@@ -288,8 +289,14 @@ void drm_gem_shmem_unpin(struct drm_gem_shmem_object *shmem)
 
 	drm_WARN_ON(obj->dev, obj->import_attach);
 
+	if (refcount_dec_not_one(&shmem->pages_pin_count))
+		return;
+
 	dma_resv_lock(shmem->base.resv, NULL);
-	drm_gem_shmem_unpin_locked(shmem);
+
+	if (refcount_dec_and_test(&shmem->pages_pin_count))
+		drm_gem_shmem_put_pages_locked(shmem);
+
 	dma_resv_unlock(shmem->base.resv);
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_unpin);
@@ -634,6 +641,7 @@ void drm_gem_shmem_print_info(const struct drm_gem_shmem_object *shmem,
 	if (shmem->base.import_attach)
 		return;
 
+	drm_printf_indent(p, indent, "pages_pin_count=%u\n", refcount_read(&shmem->pages_pin_count));
 	drm_printf_indent(p, indent, "pages_use_count=%u\n", shmem->pages_use_count);
 	drm_printf_indent(p, indent, "vmap_use_count=%u\n", shmem->vmap_use_count);
 	drm_printf_indent(p, indent, "vaddr=%p\n", shmem->vaddr);
diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
index 808083279fd5..1cd74ae5761a 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -39,6 +39,16 @@ struct drm_gem_shmem_object {
 	 */
 	unsigned int pages_use_count;
 
+	/**
+	 * @pages_pin_count:
+	 *
+	 * Reference count on the pinned pages table.
+	 * The pages allowed to be evicted and purged by memory
+	 * shrinker only when the count is zero, otherwise pages
+	 * are hard-pinned in memory.
+	 */
+	refcount_t pages_pin_count;
+
 	/**
 	 * @madv: State for madvise
 	 *
-- 
2.41.0

Re: [PATCH v16 10/20] drm/shmem-helper: Add and use pages_pin_count

[Boris Brezillon]

On Sun,  3 Sep 2023 20:07:26 +0300
Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:

> Add separate pages_pin_count for tracking of whether drm-shmem pages are
> moveable or not. With the addition of memory shrinker support to drm-shmem,
> the pages_use_count will no longer determine whether pages are hard-pinned
> in memory, but whether pages exist and are soft-pinned (and could be swapped
> out). The pages_pin_count > 1 will hard-pin pages in memory.
> 
> Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>

> ---
>  drivers/gpu/drm/drm_gem_shmem_helper.c | 24 ++++++++++++++++--------
>  include/drm/drm_gem_shmem_helper.h     | 10 ++++++++++
>  2 files changed, 26 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index 25e99468ced2..7e1e674e2c9f 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -236,18 +236,16 @@ static int drm_gem_shmem_pin_locked(struct drm_gem_shmem_object *shmem)
>  
>  	dma_resv_assert_held(shmem->base.resv);
>  
> +	if (refcount_inc_not_zero(&shmem->pages_pin_count))
> +		return 0;
> +
>  	ret = drm_gem_shmem_get_pages_locked(shmem);
> +	if (!ret)
> +		refcount_set(&shmem->pages_pin_count, 1);
>  
>  	return ret;
>  }
>  
> -static void drm_gem_shmem_unpin_locked(struct drm_gem_shmem_object *shmem)
> -{
> -	dma_resv_assert_held(shmem->base.resv);
> -
> -	drm_gem_shmem_put_pages_locked(shmem);
> -}
> -
>  /**
>   * drm_gem_shmem_pin - Pin backing pages for a shmem GEM object
>   * @shmem: shmem GEM object
> @@ -265,6 +263,9 @@ int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem)
>  
>  	drm_WARN_ON(obj->dev, obj->import_attach);
>  
> +	if (refcount_inc_not_zero(&shmem->pages_pin_count))
> +		return 0;
> +
>  	ret = dma_resv_lock_interruptible(shmem->base.resv, NULL);
>  	if (ret)
>  		return ret;
> @@ -288,8 +289,14 @@ void drm_gem_shmem_unpin(struct drm_gem_shmem_object *shmem)
>  
>  	drm_WARN_ON(obj->dev, obj->import_attach);
>  
> +	if (refcount_dec_not_one(&shmem->pages_pin_count))
> +		return;
> +
>  	dma_resv_lock(shmem->base.resv, NULL);
> -	drm_gem_shmem_unpin_locked(shmem);
> +
> +	if (refcount_dec_and_test(&shmem->pages_pin_count))
> +		drm_gem_shmem_put_pages_locked(shmem);
> +
>  	dma_resv_unlock(shmem->base.resv);
>  }
>  EXPORT_SYMBOL_GPL(drm_gem_shmem_unpin);
> @@ -634,6 +641,7 @@ void drm_gem_shmem_print_info(const struct drm_gem_shmem_object *shmem,
>  	if (shmem->base.import_attach)
>  		return;
>  
> +	drm_printf_indent(p, indent, "pages_pin_count=%u\n", refcount_read(&shmem->pages_pin_count));
>  	drm_printf_indent(p, indent, "pages_use_count=%u\n", shmem->pages_use_count);
>  	drm_printf_indent(p, indent, "vmap_use_count=%u\n", shmem->vmap_use_count);
>  	drm_printf_indent(p, indent, "vaddr=%p\n", shmem->vaddr);
> diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
> index 808083279fd5..1cd74ae5761a 100644
> --- a/include/drm/drm_gem_shmem_helper.h
> +++ b/include/drm/drm_gem_shmem_helper.h
> @@ -39,6 +39,16 @@ struct drm_gem_shmem_object {
>  	 */
>  	unsigned int pages_use_count;
>  
> +	/**
> +	 * @pages_pin_count:
> +	 *
> +	 * Reference count on the pinned pages table.
> +	 * The pages allowed to be evicted and purged by memory
> +	 * shrinker only when the count is zero, otherwise pages
> +	 * are hard-pinned in memory.
> +	 */
> +	refcount_t pages_pin_count;
> +
>  	/**
>  	 * @madv: State for madvise
>  	 *

[PATCH v16 11/20] drm/shmem-helper: Use refcount_t for pages_use_count

[Dmitry Osipenko]

Use atomic refcount_t helper for pages_use_count to optimize pin/unpin
functions by skipping reservation locking while GEM's pin refcount > 1.

Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c  | 35 +++++++++++--------------
 drivers/gpu/drm/lima/lima_gem.c         |  2 +-
 drivers/gpu/drm/panfrost/panfrost_mmu.c |  2 +-
 include/drm/drm_gem_shmem_helper.h      |  2 +-
 4 files changed, 19 insertions(+), 22 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 7e1e674e2c9f..a0faef3e762d 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -152,12 +152,12 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
 			sg_free_table(shmem->sgt);
 			kfree(shmem->sgt);
 		}
-		if (shmem->pages) {
+		if (refcount_read(&shmem->pages_use_count)) {
 			drm_gem_shmem_put_pages_locked(shmem);
 			drm_WARN_ON(obj->dev, !shmem->got_pages_sgt);
 		}
 
-		drm_WARN_ON(obj->dev, shmem->pages_use_count);
+		drm_WARN_ON(obj->dev, refcount_read(&shmem->pages_use_count));
 
 		dma_resv_unlock(shmem->base.resv);
 	}
@@ -174,14 +174,13 @@ static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
 
 	dma_resv_assert_held(shmem->base.resv);
 
-	if (shmem->pages_use_count++ > 0)
+	if (refcount_inc_not_zero(&shmem->pages_use_count))
 		return 0;
 
 	pages = drm_gem_get_pages(obj);
 	if (IS_ERR(pages)) {
 		drm_dbg_kms(obj->dev, "Failed to get pages (%ld)\n",
 			    PTR_ERR(pages));
-		shmem->pages_use_count = 0;
 		return PTR_ERR(pages);
 	}
 
@@ -197,6 +196,8 @@ static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
 
 	shmem->pages = pages;
 
+	refcount_set(&shmem->pages_use_count, 1);
+
 	return 0;
 }
 
@@ -212,21 +213,17 @@ void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
 
 	dma_resv_assert_held(shmem->base.resv);
 
-	if (drm_WARN_ON_ONCE(obj->dev, !shmem->pages_use_count))
-		return;
-
-	if (--shmem->pages_use_count > 0)
-		return;
-
+	if (refcount_dec_and_test(&shmem->pages_use_count)) {
 #ifdef CONFIG_X86
-	if (shmem->map_wc)
-		set_pages_array_wb(shmem->pages, obj->size >> PAGE_SHIFT);
+		if (shmem->map_wc)
+			set_pages_array_wb(shmem->pages, obj->size >> PAGE_SHIFT);
 #endif
 
-	drm_gem_put_pages(obj, shmem->pages,
-			  shmem->pages_mark_dirty_on_put,
-			  shmem->pages_mark_accessed_on_put);
-	shmem->pages = NULL;
+		drm_gem_put_pages(obj, shmem->pages,
+				  shmem->pages_mark_dirty_on_put,
+				  shmem->pages_mark_accessed_on_put);
+		shmem->pages = NULL;
+	}
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_put_pages_locked);
 
@@ -553,8 +550,8 @@ static void drm_gem_shmem_vm_open(struct vm_area_struct *vma)
 	 * mmap'd, vm_open() just grabs an additional reference for the new
 	 * mm the vma is getting copied into (ie. on fork()).
 	 */
-	if (!drm_WARN_ON_ONCE(obj->dev, !shmem->pages_use_count))
-		shmem->pages_use_count++;
+	drm_WARN_ON_ONCE(obj->dev,
+			 !refcount_inc_not_zero(&shmem->pages_use_count));
 
 	dma_resv_unlock(shmem->base.resv);
 
@@ -642,7 +639,7 @@ void drm_gem_shmem_print_info(const struct drm_gem_shmem_object *shmem,
 		return;
 
 	drm_printf_indent(p, indent, "pages_pin_count=%u\n", refcount_read(&shmem->pages_pin_count));
-	drm_printf_indent(p, indent, "pages_use_count=%u\n", shmem->pages_use_count);
+	drm_printf_indent(p, indent, "pages_use_count=%u\n", refcount_read(&shmem->pages_use_count));
 	drm_printf_indent(p, indent, "vmap_use_count=%u\n", shmem->vmap_use_count);
 	drm_printf_indent(p, indent, "vaddr=%p\n", shmem->vaddr);
 }
diff --git a/drivers/gpu/drm/lima/lima_gem.c b/drivers/gpu/drm/lima/lima_gem.c
index ec8f718aa539..4be2fccbf6d9 100644
--- a/drivers/gpu/drm/lima/lima_gem.c
+++ b/drivers/gpu/drm/lima/lima_gem.c
@@ -47,8 +47,8 @@ int lima_heap_alloc(struct lima_bo *bo, struct lima_vm *vm)
 		}
 
 		bo->base.pages = pages;
-		bo->base.pages_use_count = 1;
 		bo->base.got_pages_sgt = true;
+		refcount_set(&bo->base.pages_use_count, 1);
 
 		mapping_set_unevictable(mapping);
 	}
diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
index 7771769f0ce0..a91252053aa3 100644
--- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
+++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
@@ -487,7 +487,7 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
 			goto err_unlock;
 		}
 		bo->base.pages = pages;
-		bo->base.pages_use_count = 1;
+		refcount_set(&bo->base.pages_use_count, 1);
 	} else {
 		pages = bo->base.pages;
 		if (pages[page_offset]) {
diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
index 1cd74ae5761a..bd545428a7ee 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -37,7 +37,7 @@ struct drm_gem_shmem_object {
 	 * Reference count on the pages table.
 	 * The pages are put when the count reaches zero.
 	 */
-	unsigned int pages_use_count;
+	refcount_t pages_use_count;
 
 	/**
 	 * @pages_pin_count:
-- 
2.41.0

Re: [PATCH v16 11/20] drm/shmem-helper: Use refcount_t for pages_use_count

[Boris Brezillon]

On Sun,  3 Sep 2023 20:07:27 +0300
Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:

> Use atomic refcount_t helper for pages_use_count to optimize pin/unpin
> functions by skipping reservation locking while GEM's pin refcount > 1.
> 
> Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> ---
>  drivers/gpu/drm/drm_gem_shmem_helper.c  | 35 +++++++++++--------------
>  drivers/gpu/drm/lima/lima_gem.c         |  2 +-
>  drivers/gpu/drm/panfrost/panfrost_mmu.c |  2 +-
>  include/drm/drm_gem_shmem_helper.h      |  2 +-
>  4 files changed, 19 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index 7e1e674e2c9f..a0faef3e762d 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -152,12 +152,12 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
>  			sg_free_table(shmem->sgt);
>  			kfree(shmem->sgt);
>  		}
> -		if (shmem->pages) {
> +		if (refcount_read(&shmem->pages_use_count)) {

As explained in my v15 review, I'm not convinced this is the right
thing to do. We should instead move the
drm_gem_shmem_put_pages_locked() call in the preceding 'if (shmem->sgt)'
block, because the sgt creation logic is where this implicit pages ref
was taken. If shmem->sgt == NULL, there's no reason to call
drm_gem_shmem_put_pages_locked() and we should let the following
drm_WARN_ON(obj->dev, refcount_read(&shmem->pages_use_count)) complain.

Besides, I don't think this change should be part of the
uint -> refcount_t conversion.

>  			drm_gem_shmem_put_pages_locked(shmem);
>  			drm_WARN_ON(obj->dev, !shmem->got_pages_sgt);
>  		}
>  
> -		drm_WARN_ON(obj->dev, shmem->pages_use_count);
> +		drm_WARN_ON(obj->dev, refcount_read(&shmem->pages_use_count));
>  
>  		dma_resv_unlock(shmem->base.resv);
>  	}
> @@ -174,14 +174,13 @@ static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
>  
>  	dma_resv_assert_held(shmem->base.resv);
>  
> -	if (shmem->pages_use_count++ > 0)
> +	if (refcount_inc_not_zero(&shmem->pages_use_count))
>  		return 0;
>  
>  	pages = drm_gem_get_pages(obj);
>  	if (IS_ERR(pages)) {
>  		drm_dbg_kms(obj->dev, "Failed to get pages (%ld)\n",
>  			    PTR_ERR(pages));
> -		shmem->pages_use_count = 0;
>  		return PTR_ERR(pages);
>  	}
>  
> @@ -197,6 +196,8 @@ static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
>  
>  	shmem->pages = pages;
>  
> +	refcount_set(&shmem->pages_use_count, 1);
> +
>  	return 0;
>  }
>  
> @@ -212,21 +213,17 @@ void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
>  
>  	dma_resv_assert_held(shmem->base.resv);
>  
> -	if (drm_WARN_ON_ONCE(obj->dev, !shmem->pages_use_count))
> -		return;
> -
> -	if (--shmem->pages_use_count > 0)
> -		return;
> -
> +	if (refcount_dec_and_test(&shmem->pages_use_count)) {
>  #ifdef CONFIG_X86
> -	if (shmem->map_wc)
> -		set_pages_array_wb(shmem->pages, obj->size >> PAGE_SHIFT);
> +		if (shmem->map_wc)
> +			set_pages_array_wb(shmem->pages, obj->size >> PAGE_SHIFT);
>  #endif
>  
> -	drm_gem_put_pages(obj, shmem->pages,
> -			  shmem->pages_mark_dirty_on_put,
> -			  shmem->pages_mark_accessed_on_put);
> -	shmem->pages = NULL;
> +		drm_gem_put_pages(obj, shmem->pages,
> +				  shmem->pages_mark_dirty_on_put,
> +				  shmem->pages_mark_accessed_on_put);
> +		shmem->pages = NULL;
> +	}
>  }
>  EXPORT_SYMBOL_GPL(drm_gem_shmem_put_pages_locked);
>  
> @@ -553,8 +550,8 @@ static void drm_gem_shmem_vm_open(struct vm_area_struct *vma)
>  	 * mmap'd, vm_open() just grabs an additional reference for the new
>  	 * mm the vma is getting copied into (ie. on fork()).
>  	 */
> -	if (!drm_WARN_ON_ONCE(obj->dev, !shmem->pages_use_count))
> -		shmem->pages_use_count++;
> +	drm_WARN_ON_ONCE(obj->dev,
> +			 !refcount_inc_not_zero(&shmem->pages_use_count));
>  
>  	dma_resv_unlock(shmem->base.resv);
>  
> @@ -642,7 +639,7 @@ void drm_gem_shmem_print_info(const struct drm_gem_shmem_object *shmem,
>  		return;
>  
>  	drm_printf_indent(p, indent, "pages_pin_count=%u\n", refcount_read(&shmem->pages_pin_count));
> -	drm_printf_indent(p, indent, "pages_use_count=%u\n", shmem->pages_use_count);
> +	drm_printf_indent(p, indent, "pages_use_count=%u\n", refcount_read(&shmem->pages_use_count));
>  	drm_printf_indent(p, indent, "vmap_use_count=%u\n", shmem->vmap_use_count);
>  	drm_printf_indent(p, indent, "vaddr=%p\n", shmem->vaddr);
>  }
> diff --git a/drivers/gpu/drm/lima/lima_gem.c b/drivers/gpu/drm/lima/lima_gem.c
> index ec8f718aa539..4be2fccbf6d9 100644
> --- a/drivers/gpu/drm/lima/lima_gem.c
> +++ b/drivers/gpu/drm/lima/lima_gem.c
> @@ -47,8 +47,8 @@ int lima_heap_alloc(struct lima_bo *bo, struct lima_vm *vm)
>  		}
>  
>  		bo->base.pages = pages;
> -		bo->base.pages_use_count = 1;
>  		bo->base.got_pages_sgt = true;
> +		refcount_set(&bo->base.pages_use_count, 1);
>  
>  		mapping_set_unevictable(mapping);
>  	}
> diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> index 7771769f0ce0..a91252053aa3 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> @@ -487,7 +487,7 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
>  			goto err_unlock;
>  		}
>  		bo->base.pages = pages;
> -		bo->base.pages_use_count = 1;
> +		refcount_set(&bo->base.pages_use_count, 1);
>  	} else {
>  		pages = bo->base.pages;
>  		if (pages[page_offset]) {
> diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
> index 1cd74ae5761a..bd545428a7ee 100644
> --- a/include/drm/drm_gem_shmem_helper.h
> +++ b/include/drm/drm_gem_shmem_helper.h
> @@ -37,7 +37,7 @@ struct drm_gem_shmem_object {
>  	 * Reference count on the pages table.
>  	 * The pages are put when the count reaches zero.
>  	 */
> -	unsigned int pages_use_count;
> +	refcount_t pages_use_count;
>  
>  	/**
>  	 * @pages_pin_count:

[PATCH v16 12/20] drm/shmem-helper: Add and use lockless drm_gem_shmem_get_pages()

[Dmitry Osipenko]

Add lockless drm_gem_shmem_get_pages() helper that skips taking reservation
lock if pages_use_count is non-zero, leveraging from atomicity of the
refcount_t. Make drm_gem_shmem_mmap() to utilize the new helper.

Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index a0faef3e762d..d93ebfef20c7 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -227,6 +227,20 @@ void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_put_pages_locked);
 
+static int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem)
+{
+	int ret;
+
+	if (refcount_inc_not_zero(&shmem->pages_use_count))
+		return 0;
+
+	dma_resv_lock(shmem->base.resv, NULL);
+	ret = drm_gem_shmem_get_pages_locked(shmem);
+	dma_resv_unlock(shmem->base.resv);
+
+	return ret;
+}
+
 static int drm_gem_shmem_pin_locked(struct drm_gem_shmem_object *shmem)
 {
 	int ret;
@@ -610,10 +624,7 @@ int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct
 		return ret;
 	}
 
-	dma_resv_lock(shmem->base.resv, NULL);
-	ret = drm_gem_shmem_get_pages_locked(shmem);
-	dma_resv_unlock(shmem->base.resv);
-
+	ret = drm_gem_shmem_get_pages(shmem);
 	if (ret)
 		return ret;
 
-- 
2.41.0

Re: [PATCH v16 12/20] drm/shmem-helper: Add and use lockless drm_gem_shmem_get_pages()

[Boris Brezillon]

On Sun,  3 Sep 2023 20:07:28 +0300
Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:

> Add lockless drm_gem_shmem_get_pages() helper that skips taking reservation
> lock if pages_use_count is non-zero, leveraging from atomicity of the
> refcount_t. Make drm_gem_shmem_mmap() to utilize the new helper.
> 
> Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>

> ---
>  drivers/gpu/drm/drm_gem_shmem_helper.c | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index a0faef3e762d..d93ebfef20c7 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -227,6 +227,20 @@ void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
>  }
>  EXPORT_SYMBOL_GPL(drm_gem_shmem_put_pages_locked);
>  
> +static int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem)
> +{
> +	int ret;
> +
> +	if (refcount_inc_not_zero(&shmem->pages_use_count))
> +		return 0;
> +
> +	dma_resv_lock(shmem->base.resv, NULL);
> +	ret = drm_gem_shmem_get_pages_locked(shmem);
> +	dma_resv_unlock(shmem->base.resv);
> +
> +	return ret;
> +}
> +
>  static int drm_gem_shmem_pin_locked(struct drm_gem_shmem_object *shmem)
>  {
>  	int ret;
> @@ -610,10 +624,7 @@ int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct
>  		return ret;
>  	}
>  
> -	dma_resv_lock(shmem->base.resv, NULL);
> -	ret = drm_gem_shmem_get_pages_locked(shmem);
> -	dma_resv_unlock(shmem->base.resv);
> -
> +	ret = drm_gem_shmem_get_pages(shmem);
>  	if (ret)
>  		return ret;
>  

[PATCH v16 13/20] drm/shmem-helper: Switch drm_gem_shmem_vmap/vunmap to use pin/unpin

[Dmitry Osipenko]

The vmapped pages shall be pinned in memory and previously get/put_pages()
were implicitly hard-pinning/unpinning the pages. This will no longer be
the case with addition of memory shrinker because pages_use_count > 0 won't
determine anymore whether pages are hard-pinned (they will be soft-pinned),
while the new pages_pin_count will do the hard-pinning. Switch the
vmap/vunmap() to use pin/unpin() functions in a preparation of addition
of the memory shrinker support to drm-shmem.

Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 19 ++++++++++++-------
 include/drm/drm_gem_shmem_helper.h     |  2 +-
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index d93ebfef20c7..899f655a65bb 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -257,6 +257,14 @@ static int drm_gem_shmem_pin_locked(struct drm_gem_shmem_object *shmem)
 	return ret;
 }
 
+static void drm_gem_shmem_unpin_locked(struct drm_gem_shmem_object *shmem)
+{
+	dma_resv_assert_held(shmem->base.resv);
+
+	if (refcount_dec_and_test(&shmem->pages_pin_count))
+		drm_gem_shmem_put_pages_locked(shmem);
+}
+
 /**
  * drm_gem_shmem_pin - Pin backing pages for a shmem GEM object
  * @shmem: shmem GEM object
@@ -304,10 +312,7 @@ void drm_gem_shmem_unpin(struct drm_gem_shmem_object *shmem)
 		return;
 
 	dma_resv_lock(shmem->base.resv, NULL);
-
-	if (refcount_dec_and_test(&shmem->pages_pin_count))
-		drm_gem_shmem_put_pages_locked(shmem);
-
+	drm_gem_shmem_unpin_locked(shmem);
 	dma_resv_unlock(shmem->base.resv);
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_unpin);
@@ -345,7 +350,7 @@ int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem,
 			return 0;
 		}
 
-		ret = drm_gem_shmem_get_pages_locked(shmem);
+		ret = drm_gem_shmem_pin_locked(shmem);
 		if (ret)
 			goto err_zero_use;
 
@@ -368,7 +373,7 @@ int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem,
 
 err_put_pages:
 	if (!obj->import_attach)
-		drm_gem_shmem_put_pages_locked(shmem);
+		drm_gem_shmem_unpin_locked(shmem);
 err_zero_use:
 	shmem->vmap_use_count = 0;
 
@@ -405,7 +410,7 @@ void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem,
 			return;
 
 		vunmap(shmem->vaddr);
-		drm_gem_shmem_put_pages_locked(shmem);
+		drm_gem_shmem_unpin_locked(shmem);
 	}
 
 	shmem->vaddr = NULL;
diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
index bd545428a7ee..396958a98c34 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -137,7 +137,7 @@ int drm_gem_shmem_madvise_locked(struct drm_gem_shmem_object *shmem, int madv);
 static inline bool drm_gem_shmem_is_purgeable(struct drm_gem_shmem_object *shmem)
 {
 	return (shmem->madv > 0) &&
-		!shmem->vmap_use_count && shmem->sgt &&
+		!refcount_read(&shmem->pages_pin_count) && shmem->sgt &&
 		!shmem->base.dma_buf && !shmem->base.import_attach;
 }
 
-- 
2.41.0

Re: [PATCH v16 13/20] drm/shmem-helper: Switch drm_gem_shmem_vmap/vunmap to use pin/unpin

[Boris Brezillon]

On Sun,  3 Sep 2023 20:07:29 +0300
Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:

> The vmapped pages shall be pinned in memory and previously get/put_pages()
> were implicitly hard-pinning/unpinning the pages. This will no longer be
> the case with addition of memory shrinker because pages_use_count > 0 won't
> determine anymore whether pages are hard-pinned (they will be soft-pinned),
> while the new pages_pin_count will do the hard-pinning. Switch the
> vmap/vunmap() to use pin/unpin() functions in a preparation of addition
> of the memory shrinker support to drm-shmem.
> 
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>

> ---
>  drivers/gpu/drm/drm_gem_shmem_helper.c | 19 ++++++++++++-------
>  include/drm/drm_gem_shmem_helper.h     |  2 +-
>  2 files changed, 13 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index d93ebfef20c7..899f655a65bb 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -257,6 +257,14 @@ static int drm_gem_shmem_pin_locked(struct drm_gem_shmem_object *shmem)
>  	return ret;
>  }
>  
> +static void drm_gem_shmem_unpin_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	dma_resv_assert_held(shmem->base.resv);
> +
> +	if (refcount_dec_and_test(&shmem->pages_pin_count))
> +		drm_gem_shmem_put_pages_locked(shmem);
> +}
> +
>  /**
>   * drm_gem_shmem_pin - Pin backing pages for a shmem GEM object
>   * @shmem: shmem GEM object
> @@ -304,10 +312,7 @@ void drm_gem_shmem_unpin(struct drm_gem_shmem_object *shmem)
>  		return;
>  
>  	dma_resv_lock(shmem->base.resv, NULL);
> -
> -	if (refcount_dec_and_test(&shmem->pages_pin_count))
> -		drm_gem_shmem_put_pages_locked(shmem);
> -
> +	drm_gem_shmem_unpin_locked(shmem);
>  	dma_resv_unlock(shmem->base.resv);
>  }
>  EXPORT_SYMBOL_GPL(drm_gem_shmem_unpin);
> @@ -345,7 +350,7 @@ int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem,
>  			return 0;
>  		}
>  
> -		ret = drm_gem_shmem_get_pages_locked(shmem);
> +		ret = drm_gem_shmem_pin_locked(shmem);
>  		if (ret)
>  			goto err_zero_use;
>  
> @@ -368,7 +373,7 @@ int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem,
>  
>  err_put_pages:
>  	if (!obj->import_attach)
> -		drm_gem_shmem_put_pages_locked(shmem);
> +		drm_gem_shmem_unpin_locked(shmem);
>  err_zero_use:
>  	shmem->vmap_use_count = 0;
>  
> @@ -405,7 +410,7 @@ void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem,
>  			return;
>  
>  		vunmap(shmem->vaddr);
> -		drm_gem_shmem_put_pages_locked(shmem);
> +		drm_gem_shmem_unpin_locked(shmem);
>  	}
>  
>  	shmem->vaddr = NULL;
> diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
> index bd545428a7ee..396958a98c34 100644
> --- a/include/drm/drm_gem_shmem_helper.h
> +++ b/include/drm/drm_gem_shmem_helper.h
> @@ -137,7 +137,7 @@ int drm_gem_shmem_madvise_locked(struct drm_gem_shmem_object *shmem, int madv);
>  static inline bool drm_gem_shmem_is_purgeable(struct drm_gem_shmem_object *shmem)
>  {
>  	return (shmem->madv > 0) &&
> -		!shmem->vmap_use_count && shmem->sgt &&
> +		!refcount_read(&shmem->pages_pin_count) && shmem->sgt &&
>  		!shmem->base.dma_buf && !shmem->base.import_attach;
>  }
>  

[PATCH v16 14/20] drm/shmem-helper: Use refcount_t for vmap_use_count

[Dmitry Osipenko]

Use refcount_t helper for vmap_use_count to make refcounting consistent
with pages_use_count and pages_pin_count that use refcount_t. This will
allow to optimize unlocked vmappings by skipping reservation locking if
refcnt > 1 and also makes vmapping to benefit from the refcount_t's
overflow checks.

Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 28 +++++++++++---------------
 include/drm/drm_gem_shmem_helper.h     |  2 +-
 2 files changed, 13 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 899f655a65bb..4633a418faba 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -144,7 +144,7 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
 	} else if (!shmem->imported_sgt) {
 		dma_resv_lock(shmem->base.resv, NULL);
 
-		drm_WARN_ON(obj->dev, shmem->vmap_use_count);
+		drm_WARN_ON(obj->dev, refcount_read(&shmem->vmap_use_count));
 
 		if (shmem->sgt) {
 			dma_unmap_sgtable(obj->dev->dev, shmem->sgt,
@@ -345,23 +345,25 @@ int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem,
 
 		dma_resv_assert_held(shmem->base.resv);
 
-		if (shmem->vmap_use_count++ > 0) {
+		if (refcount_inc_not_zero(&shmem->vmap_use_count)) {
 			iosys_map_set_vaddr(map, shmem->vaddr);
 			return 0;
 		}
 
 		ret = drm_gem_shmem_pin_locked(shmem);
 		if (ret)
-			goto err_zero_use;
+			return ret;
 
 		if (shmem->map_wc)
 			prot = pgprot_writecombine(prot);
 		shmem->vaddr = vmap(shmem->pages, obj->size >> PAGE_SHIFT,
 				    VM_MAP, prot);
-		if (!shmem->vaddr)
+		if (!shmem->vaddr) {
 			ret = -ENOMEM;
-		else
+		} else {
 			iosys_map_set_vaddr(map, shmem->vaddr);
+			refcount_set(&shmem->vmap_use_count, 1);
+		}
 	}
 
 	if (ret) {
@@ -374,8 +376,6 @@ int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem,
 err_put_pages:
 	if (!obj->import_attach)
 		drm_gem_shmem_unpin_locked(shmem);
-err_zero_use:
-	shmem->vmap_use_count = 0;
 
 	return ret;
 }
@@ -403,14 +403,10 @@ void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem,
 	} else {
 		dma_resv_assert_held(shmem->base.resv);
 
-		if (drm_WARN_ON_ONCE(obj->dev, !shmem->vmap_use_count))
-			return;
-
-		if (--shmem->vmap_use_count > 0)
-			return;
-
-		vunmap(shmem->vaddr);
-		drm_gem_shmem_unpin_locked(shmem);
+		if (refcount_dec_and_test(&shmem->vmap_use_count)) {
+			vunmap(shmem->vaddr);
+			drm_gem_shmem_unpin_locked(shmem);
+		}
 	}
 
 	shmem->vaddr = NULL;
@@ -656,7 +652,7 @@ void drm_gem_shmem_print_info(const struct drm_gem_shmem_object *shmem,
 
 	drm_printf_indent(p, indent, "pages_pin_count=%u\n", refcount_read(&shmem->pages_pin_count));
 	drm_printf_indent(p, indent, "pages_use_count=%u\n", refcount_read(&shmem->pages_use_count));
-	drm_printf_indent(p, indent, "vmap_use_count=%u\n", shmem->vmap_use_count);
+	drm_printf_indent(p, indent, "vmap_use_count=%u\n", refcount_read(&shmem->vmap_use_count));
 	drm_printf_indent(p, indent, "vaddr=%p\n", shmem->vaddr);
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_print_info);
diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
index 396958a98c34..63e91e8f2d5c 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -81,7 +81,7 @@ struct drm_gem_shmem_object {
 	 * Reference count on the virtual address.
 	 * The address are un-mapped when the count reaches zero.
 	 */
-	unsigned int vmap_use_count;
+	refcount_t vmap_use_count;
 
 	/**
 	 * @got_pages_sgt:
-- 
2.41.0

Re: [PATCH v16 14/20] drm/shmem-helper: Use refcount_t for vmap_use_count

[Boris Brezillon]

On Sun,  3 Sep 2023 20:07:30 +0300
Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:

> Use refcount_t helper for vmap_use_count to make refcounting consistent
> with pages_use_count and pages_pin_count that use refcount_t. This will
> allow to optimize unlocked vmappings by skipping reservation locking if
> refcnt > 1

nit: this optimization doesn't exist in practice, because the resv
lock is taken by the core, and ->v[un]map() are called with this lock
held.

> and also makes vmapping to benefit from the refcount_t's
> overflow checks.
> 
> Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>

I agree with your 2 other points (consistency with other refcounting
primitives and safeness provided by refcount_t) so

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>

but I'd recommend rephrasing/dropping the part mentioning the lock-free
optimization.

> ---
>  drivers/gpu/drm/drm_gem_shmem_helper.c | 28 +++++++++++---------------
>  include/drm/drm_gem_shmem_helper.h     |  2 +-
>  2 files changed, 13 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index 899f655a65bb..4633a418faba 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -144,7 +144,7 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
>  	} else if (!shmem->imported_sgt) {
>  		dma_resv_lock(shmem->base.resv, NULL);
>  
> -		drm_WARN_ON(obj->dev, shmem->vmap_use_count);
> +		drm_WARN_ON(obj->dev, refcount_read(&shmem->vmap_use_count));
>  
>  		if (shmem->sgt) {
>  			dma_unmap_sgtable(obj->dev->dev, shmem->sgt,
> @@ -345,23 +345,25 @@ int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem,
>  
>  		dma_resv_assert_held(shmem->base.resv);
>  
> -		if (shmem->vmap_use_count++ > 0) {
> +		if (refcount_inc_not_zero(&shmem->vmap_use_count)) {
>  			iosys_map_set_vaddr(map, shmem->vaddr);
>  			return 0;
>  		}
>  
>  		ret = drm_gem_shmem_pin_locked(shmem);
>  		if (ret)
> -			goto err_zero_use;
> +			return ret;
>  
>  		if (shmem->map_wc)
>  			prot = pgprot_writecombine(prot);
>  		shmem->vaddr = vmap(shmem->pages, obj->size >> PAGE_SHIFT,
>  				    VM_MAP, prot);
> -		if (!shmem->vaddr)
> +		if (!shmem->vaddr) {
>  			ret = -ENOMEM;
> -		else
> +		} else {
>  			iosys_map_set_vaddr(map, shmem->vaddr);
> +			refcount_set(&shmem->vmap_use_count, 1);
> +		}
>  	}
>  
>  	if (ret) {
> @@ -374,8 +376,6 @@ int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem,
>  err_put_pages:
>  	if (!obj->import_attach)
>  		drm_gem_shmem_unpin_locked(shmem);
> -err_zero_use:
> -	shmem->vmap_use_count = 0;
>  
>  	return ret;
>  }
> @@ -403,14 +403,10 @@ void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem,
>  	} else {
>  		dma_resv_assert_held(shmem->base.resv);
>  
> -		if (drm_WARN_ON_ONCE(obj->dev, !shmem->vmap_use_count))
> -			return;
> -
> -		if (--shmem->vmap_use_count > 0)
> -			return;
> -
> -		vunmap(shmem->vaddr);
> -		drm_gem_shmem_unpin_locked(shmem);
> +		if (refcount_dec_and_test(&shmem->vmap_use_count)) {
> +			vunmap(shmem->vaddr);
> +			drm_gem_shmem_unpin_locked(shmem);
> +		}
>  	}
>  
>  	shmem->vaddr = NULL;
> @@ -656,7 +652,7 @@ void drm_gem_shmem_print_info(const struct drm_gem_shmem_object *shmem,
>  
>  	drm_printf_indent(p, indent, "pages_pin_count=%u\n", refcount_read(&shmem->pages_pin_count));
>  	drm_printf_indent(p, indent, "pages_use_count=%u\n", refcount_read(&shmem->pages_use_count));
> -	drm_printf_indent(p, indent, "vmap_use_count=%u\n", shmem->vmap_use_count);
> +	drm_printf_indent(p, indent, "vmap_use_count=%u\n", refcount_read(&shmem->vmap_use_count));
>  	drm_printf_indent(p, indent, "vaddr=%p\n", shmem->vaddr);
>  }
>  EXPORT_SYMBOL_GPL(drm_gem_shmem_print_info);
> diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
> index 396958a98c34..63e91e8f2d5c 100644
> --- a/include/drm/drm_gem_shmem_helper.h
> +++ b/include/drm/drm_gem_shmem_helper.h
> @@ -81,7 +81,7 @@ struct drm_gem_shmem_object {
>  	 * Reference count on the virtual address.
>  	 * The address are un-mapped when the count reaches zero.
>  	 */
> -	unsigned int vmap_use_count;
> +	refcount_t vmap_use_count;
>  
>  	/**
>  	 * @got_pages_sgt:

[PATCH v16 15/20] drm/shmem-helper: Add memory shrinker

[Dmitry Osipenko]

Introduce common drm-shmem shrinker for DRM drivers.

To start using drm-shmem shrinker drivers should do the following:

1. Implement evict() callback of GEM object where driver should check
   whether object is purgeable or evictable using drm-shmem helpers and
   perform the shrinking action

2. Initialize drm-shmem internals using drmm_gem_shmem_init(drm_device),
   which will register drm-shmem shrinker

3. Implement madvise IOCTL that will use drm_gem_shmem_madvise()

Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c        | 442 ++++++++++++++++--
 .../gpu/drm/panfrost/panfrost_gem_shrinker.c  |   9 +-
 include/drm/drm_device.h                      |  10 +-
 include/drm/drm_gem_shmem_helper.h            |  71 ++-
 4 files changed, 494 insertions(+), 38 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 4633a418faba..a0a6c7e505c8 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -20,6 +20,7 @@
 #include <drm/drm_device.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_gem_shmem_helper.h>
+#include <drm/drm_managed.h>
 #include <drm/drm_prime.h>
 #include <drm/drm_print.h>
 
@@ -88,8 +89,6 @@ __drm_gem_shmem_create(struct drm_device *dev, size_t size, bool private)
 	if (ret)
 		goto err_release;
 
-	INIT_LIST_HEAD(&shmem->madv_list);
-
 	if (!private) {
 		/*
 		 * Our buffers are kept pinned, so allocating them
@@ -128,6 +127,62 @@ struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_create);
 
+static bool drm_gem_shmem_is_evictable(struct drm_gem_shmem_object *shmem)
+{
+	dma_resv_assert_held(shmem->base.resv);
+
+	return (shmem->madv >= 0) && shmem->base.funcs->evict &&
+		refcount_read(&shmem->pages_use_count) &&
+		!refcount_read(&shmem->pages_pin_count) &&
+		!shmem->base.dma_buf && !shmem->base.import_attach &&
+		shmem->sgt && !shmem->evicted;
+}
+
+static void
+drm_gem_shmem_update_pages_state_locked(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
+	struct drm_gem_shmem *shmem_mm = obj->dev->shmem_mm;
+	struct drm_gem_shmem_shrinker *shmem_shrinker = &shmem_mm->shrinker;
+
+	dma_resv_assert_held(shmem->base.resv);
+
+	if (!shmem_shrinker || obj->import_attach)
+		return;
+
+	if (shmem->madv < 0)
+		drm_gem_lru_remove(&shmem->base);
+	else if (drm_gem_shmem_is_evictable(shmem) || drm_gem_shmem_is_purgeable(shmem))
+		drm_gem_lru_move_tail(&shmem_shrinker->lru_evictable, &shmem->base);
+	else if (shmem->evicted)
+		drm_gem_lru_move_tail(&shmem_shrinker->lru_evicted, &shmem->base);
+	else if (!shmem->pages)
+		drm_gem_lru_remove(&shmem->base);
+	else
+		drm_gem_lru_move_tail(&shmem_shrinker->lru_pinned, &shmem->base);
+}
+
+static void
+drm_gem_shmem_do_release_pages_locked(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
+
+	if (!shmem->pages) {
+		drm_WARN_ON(obj->dev, !shmem->evicted && shmem->madv >= 0);
+		return;
+	}
+
+#ifdef CONFIG_X86
+	if (shmem->map_wc)
+		set_pages_array_wb(shmem->pages, obj->size >> PAGE_SHIFT);
+#endif
+
+	drm_gem_put_pages(obj, shmem->pages,
+			  shmem->pages_mark_dirty_on_put,
+			  shmem->pages_mark_accessed_on_put);
+	shmem->pages = NULL;
+}
+
 /**
  * drm_gem_shmem_free - Free resources associated with a shmem GEM object
  * @shmem: shmem GEM object to free
@@ -142,8 +197,6 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
 	if (obj->import_attach) {
 		drm_prime_gem_destroy(obj, shmem->sgt);
 	} else if (!shmem->imported_sgt) {
-		dma_resv_lock(shmem->base.resv, NULL);
-
 		drm_WARN_ON(obj->dev, refcount_read(&shmem->vmap_use_count));
 
 		if (shmem->sgt) {
@@ -152,14 +205,27 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
 			sg_free_table(shmem->sgt);
 			kfree(shmem->sgt);
 		}
-		if (refcount_read(&shmem->pages_use_count)) {
-			drm_gem_shmem_put_pages_locked(shmem);
-			drm_WARN_ON(obj->dev, !shmem->got_pages_sgt);
+
+		/*
+		 * Destroying the object is a special case.. drm_gem_shmem_free()
+		 * calls many things that WARN_ON if the obj lock is not held.  But
+		 * acquiring the obj lock in drm_gem_shmem_release_pages_locked() can
+		 * cause a locking order inversion between reservation_ww_class_mutex
+		 * and fs_reclaim.
+		 *
+		 * This deadlock is not actually possible, because no one should
+		 * be already holding the lock when drm_gem_shmem_free() is called.
+		 * Unfortunately lockdep is not aware of this detail.  So when the
+		 * refcount drops to zero, don't touch the reservation lock.
+		 */
+		if (shmem->got_pages_sgt &&
+		    refcount_dec_and_test(&shmem->pages_use_count)) {
+			drm_gem_shmem_do_release_pages_locked(shmem);
+			shmem->got_pages_sgt = false;
 		}
 
 		drm_WARN_ON(obj->dev, refcount_read(&shmem->pages_use_count));
-
-		dma_resv_unlock(shmem->base.resv);
+		drm_WARN_ON(obj->dev, shmem->got_pages_sgt);
 	}
 
 	drm_gem_object_release(obj);
@@ -167,15 +233,26 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_free);
 
-static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
+static int
+drm_gem_shmem_acquire_pages(struct drm_gem_shmem_object *shmem, bool init)
 {
 	struct drm_gem_object *obj = &shmem->base;
 	struct page **pages;
 
 	dma_resv_assert_held(shmem->base.resv);
 
-	if (refcount_inc_not_zero(&shmem->pages_use_count))
+	if (shmem->madv < 0) {
+		drm_WARN_ON(obj->dev, shmem->pages);
+		return -ENOMEM;
+	}
+
+	if (shmem->pages) {
+		drm_WARN_ON(obj->dev, !shmem->evicted);
 		return 0;
+	}
+
+	if (drm_WARN_ON(obj->dev, !(init ^ refcount_read(&shmem->pages_use_count))))
+		return -EINVAL;
 
 	pages = drm_gem_get_pages(obj);
 	if (IS_ERR(pages)) {
@@ -196,8 +273,36 @@ static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
 
 	shmem->pages = pages;
 
+	return 0;
+}
+
+static void
+drm_gem_shmem_release_pages_locked(struct drm_gem_shmem_object *shmem)
+{
+	dma_resv_assert_held(shmem->base.resv);
+	drm_gem_shmem_do_release_pages_locked(shmem);
+}
+
+static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
+{
+	int err;
+
+	dma_resv_assert_held(shmem->base.resv);
+
+	if (shmem->madv < 0)
+		return -ENOMEM;
+
+	if (refcount_inc_not_zero(&shmem->pages_use_count))
+		return 0;
+
+	err = drm_gem_shmem_acquire_pages(shmem, true);
+	if (err)
+		return err;
+
 	refcount_set(&shmem->pages_use_count, 1);
 
+	drm_gem_shmem_update_pages_state_locked(shmem);
+
 	return 0;
 }
 
@@ -209,20 +314,11 @@ static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
  */
 void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
 {
-	struct drm_gem_object *obj = &shmem->base;
-
 	dma_resv_assert_held(shmem->base.resv);
 
 	if (refcount_dec_and_test(&shmem->pages_use_count)) {
-#ifdef CONFIG_X86
-		if (shmem->map_wc)
-			set_pages_array_wb(shmem->pages, obj->size >> PAGE_SHIFT);
-#endif
-
-		drm_gem_put_pages(obj, shmem->pages,
-				  shmem->pages_mark_dirty_on_put,
-				  shmem->pages_mark_accessed_on_put);
-		shmem->pages = NULL;
+		drm_gem_shmem_release_pages_locked(shmem);
+		drm_gem_shmem_update_pages_state_locked(shmem);
 	}
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_put_pages_locked);
@@ -251,8 +347,15 @@ static int drm_gem_shmem_pin_locked(struct drm_gem_shmem_object *shmem)
 		return 0;
 
 	ret = drm_gem_shmem_get_pages_locked(shmem);
-	if (!ret)
+	if (!ret) {
+		ret = drm_gem_shmem_swapin_locked(shmem);
+		if (ret) {
+			drm_gem_shmem_put_pages_locked(shmem);
+			return ret;
+		}
+
 		refcount_set(&shmem->pages_pin_count, 1);
+	}
 
 	return ret;
 }
@@ -448,29 +551,54 @@ int drm_gem_shmem_madvise_locked(struct drm_gem_shmem_object *shmem, int madv)
 
 	madv = shmem->madv;
 
+	drm_gem_shmem_update_pages_state_locked(shmem);
+
 	return (madv >= 0);
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_madvise_locked);
 
-void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem)
+int drm_gem_shmem_madvise(struct drm_gem_shmem_object *shmem, int madv)
+{
+	struct drm_gem_object *obj = &shmem->base;
+	int ret;
+
+	ret = dma_resv_lock_interruptible(obj->resv, NULL);
+	if (ret)
+		return ret;
+
+	ret = drm_gem_shmem_madvise_locked(shmem, madv);
+	dma_resv_unlock(obj->resv);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_madvise);
+
+static void drm_gem_shmem_unpin_pages_locked(struct drm_gem_shmem_object *shmem)
 {
 	struct drm_gem_object *obj = &shmem->base;
 	struct drm_device *dev = obj->dev;
 
 	dma_resv_assert_held(shmem->base.resv);
 
-	drm_WARN_ON(obj->dev, !drm_gem_shmem_is_purgeable(shmem));
+	if (shmem->evicted)
+		return;
 
 	dma_unmap_sgtable(dev->dev, shmem->sgt, DMA_BIDIRECTIONAL, 0);
+	drm_gem_shmem_release_pages_locked(shmem);
+	drm_vma_node_unmap(&obj->vma_node, dev->anon_inode->i_mapping);
+
 	sg_free_table(shmem->sgt);
 	kfree(shmem->sgt);
 	shmem->sgt = NULL;
+}
 
-	drm_gem_shmem_put_pages_locked(shmem);
+void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
 
-	shmem->madv = -1;
+	drm_WARN_ON(obj->dev, !drm_gem_shmem_is_purgeable(shmem));
 
-	drm_vma_node_unmap(&obj->vma_node, dev->anon_inode->i_mapping);
+	drm_gem_shmem_unpin_pages_locked(shmem);
 	drm_gem_free_mmap_offset(obj);
 
 	/* Our goal here is to return as much of the memory as
@@ -481,9 +609,59 @@ void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem)
 	shmem_truncate_range(file_inode(obj->filp), 0, (loff_t)-1);
 
 	invalidate_mapping_pages(file_inode(obj->filp)->i_mapping, 0, (loff_t)-1);
+
+	shmem->madv = -1;
+	shmem->evicted = false;
+	drm_gem_shmem_update_pages_state_locked(shmem);
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_purge_locked);
 
+/**
+ * drm_gem_shmem_swapin_locked() - Moves shmem GEM back to memory and enables
+ *                                 hardware access to the memory.
+ * @shmem: shmem GEM object
+ *
+ * This function moves shmem GEM back to memory if it was previously evicted
+ * by the memory shrinker. The GEM is ready to use on success.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_gem_shmem_swapin_locked(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
+	struct sg_table *sgt;
+	int err;
+
+	dma_resv_assert_held(shmem->base.resv);
+
+	if (shmem->evicted) {
+		err = drm_gem_shmem_acquire_pages(shmem, false);
+		if (err)
+			return err;
+
+		sgt = drm_gem_shmem_get_sg_table(shmem);
+		if (IS_ERR(sgt))
+			return PTR_ERR(sgt);
+
+		err = dma_map_sgtable(obj->dev->dev, sgt,
+				      DMA_BIDIRECTIONAL, 0);
+		if (err) {
+			sg_free_table(sgt);
+			kfree(sgt);
+			return err;
+		}
+
+		shmem->sgt = sgt;
+		shmem->evicted = false;
+
+		drm_gem_shmem_update_pages_state_locked(shmem);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_swapin_locked);
+
 /**
  * drm_gem_shmem_dumb_create - Create a dumb shmem buffer object
  * @file: DRM file structure to create the dumb buffer for
@@ -530,22 +708,34 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
 	vm_fault_t ret;
 	struct page *page;
 	pgoff_t page_offset;
+	bool pages_unpinned;
+	int err;
 
 	/* We don't use vmf->pgoff since that has the fake offset */
 	page_offset = (vmf->address - vma->vm_start) >> PAGE_SHIFT;
 
 	dma_resv_lock(shmem->base.resv, NULL);
 
-	if (page_offset >= num_pages ||
-	    drm_WARN_ON_ONCE(obj->dev, !shmem->pages) ||
-	    shmem->madv < 0) {
+	/* Sanity-check that we have the pages pointer when it should present */
+	pages_unpinned = (shmem->evicted || shmem->madv < 0 ||
+			  !refcount_read(&shmem->pages_use_count));
+	drm_WARN_ON_ONCE(obj->dev, !shmem->pages ^ pages_unpinned);
+
+	if (page_offset >= num_pages || (!shmem->pages && !shmem->evicted)) {
 		ret = VM_FAULT_SIGBUS;
 	} else {
+		err = drm_gem_shmem_swapin_locked(shmem);
+		if (err) {
+			ret = VM_FAULT_OOM;
+			goto unlock;
+		}
+
 		page = shmem->pages[page_offset];
 
 		ret = vmf_insert_pfn(vma, vmf->address, page_to_pfn(page));
 	}
 
+unlock:
 	dma_resv_unlock(shmem->base.resv);
 
 	return ret;
@@ -568,6 +758,7 @@ static void drm_gem_shmem_vm_open(struct vm_area_struct *vma)
 	drm_WARN_ON_ONCE(obj->dev,
 			 !refcount_inc_not_zero(&shmem->pages_use_count));
 
+	drm_gem_shmem_update_pages_state_locked(shmem);
 	dma_resv_unlock(shmem->base.resv);
 
 	drm_gem_vm_open(vma);
@@ -653,7 +844,9 @@ void drm_gem_shmem_print_info(const struct drm_gem_shmem_object *shmem,
 	drm_printf_indent(p, indent, "pages_pin_count=%u\n", refcount_read(&shmem->pages_pin_count));
 	drm_printf_indent(p, indent, "pages_use_count=%u\n", refcount_read(&shmem->pages_use_count));
 	drm_printf_indent(p, indent, "vmap_use_count=%u\n", refcount_read(&shmem->vmap_use_count));
+	drm_printf_indent(p, indent, "evicted=%d\n", shmem->evicted);
 	drm_printf_indent(p, indent, "vaddr=%p\n", shmem->vaddr);
+	drm_printf_indent(p, indent, "madv=%d\n", shmem->madv);
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_print_info);
 
@@ -715,6 +908,8 @@ static struct sg_table *drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_
 
 	shmem->sgt = sgt;
 
+	drm_gem_shmem_update_pages_state_locked(shmem);
+
 	return sgt;
 
 err_free_sgt:
@@ -802,6 +997,191 @@ drm_gem_shmem_prime_import_sg_table(struct drm_device *dev,
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_prime_import_sg_table);
 
+static struct drm_gem_shmem_shrinker *
+to_drm_gem_shmem_shrinker(struct shrinker *shrinker)
+{
+	return container_of(shrinker, struct drm_gem_shmem_shrinker, base);
+}
+
+static unsigned long
+drm_gem_shmem_shrinker_count_objects(struct shrinker *shrinker,
+				     struct shrink_control *sc)
+{
+	struct drm_gem_shmem_shrinker *shmem_shrinker =
+					to_drm_gem_shmem_shrinker(shrinker);
+	unsigned long count = shmem_shrinker->lru_evictable.count;
+
+	if (count >= SHRINK_EMPTY)
+		return SHRINK_EMPTY - 1;
+
+	return count ?: SHRINK_EMPTY;
+}
+
+void drm_gem_shmem_evict_locked(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
+
+	drm_WARN_ON(obj->dev, !drm_gem_shmem_is_evictable(shmem));
+	drm_WARN_ON(obj->dev, shmem->evicted);
+
+	drm_gem_shmem_unpin_pages_locked(shmem);
+
+	shmem->evicted = true;
+	drm_gem_shmem_update_pages_state_locked(shmem);
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_evict_locked);
+
+static bool drm_gem_shmem_shrinker_evict_locked(struct drm_gem_object *obj)
+{
+	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
+	int err;
+
+	if (!drm_gem_shmem_is_evictable(shmem) ||
+	    get_nr_swap_pages() < obj->size >> PAGE_SHIFT)
+		return false;
+
+	err = drm_gem_evict_locked(obj);
+	if (err)
+		return false;
+
+	return true;
+}
+
+static bool drm_gem_shmem_shrinker_purge_locked(struct drm_gem_object *obj)
+{
+	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
+	int err;
+
+	if (!drm_gem_shmem_is_purgeable(shmem))
+		return false;
+
+	err = drm_gem_evict_locked(obj);
+	if (err)
+		return false;
+
+	return true;
+}
+
+static unsigned long
+drm_gem_shmem_shrinker_scan_objects(struct shrinker *shrinker,
+				    struct shrink_control *sc)
+{
+	struct drm_gem_shmem_shrinker *shmem_shrinker;
+	unsigned long nr_to_scan = sc->nr_to_scan;
+	unsigned long remaining = 0;
+	unsigned long freed = 0;
+
+	shmem_shrinker = to_drm_gem_shmem_shrinker(shrinker);
+
+	/* purge as many objects as we can */
+	freed += drm_gem_lru_scan(&shmem_shrinker->lru_evictable,
+				  nr_to_scan, &remaining,
+				  drm_gem_shmem_shrinker_purge_locked);
+
+	/* evict as many objects as we can */
+	if (freed < nr_to_scan)
+		freed += drm_gem_lru_scan(&shmem_shrinker->lru_evictable,
+					  nr_to_scan - freed, &remaining,
+					  drm_gem_shmem_shrinker_evict_locked);
+
+	return (freed > 0 && remaining > 0) ? freed : SHRINK_STOP;
+}
+
+static int drm_gem_shmem_shrinker_init(struct drm_gem_shmem *shmem_mm,
+				       const char *shrinker_name)
+{
+	struct drm_gem_shmem_shrinker *shmem_shrinker = &shmem_mm->shrinker;
+	int err;
+
+	shmem_shrinker->base.count_objects = drm_gem_shmem_shrinker_count_objects;
+	shmem_shrinker->base.scan_objects = drm_gem_shmem_shrinker_scan_objects;
+	shmem_shrinker->base.seeks = DEFAULT_SEEKS;
+
+	mutex_init(&shmem_shrinker->lock);
+	drm_gem_lru_init(&shmem_shrinker->lru_evictable, &shmem_shrinker->lock);
+	drm_gem_lru_init(&shmem_shrinker->lru_evicted, &shmem_shrinker->lock);
+	drm_gem_lru_init(&shmem_shrinker->lru_pinned, &shmem_shrinker->lock);
+
+	err = register_shrinker(&shmem_shrinker->base, shrinker_name);
+	if (err) {
+		mutex_destroy(&shmem_shrinker->lock);
+		return err;
+	}
+
+	return 0;
+}
+
+static void drm_gem_shmem_shrinker_release(struct drm_device *dev,
+					   struct drm_gem_shmem *shmem_mm)
+{
+	struct drm_gem_shmem_shrinker *shmem_shrinker = &shmem_mm->shrinker;
+
+	unregister_shrinker(&shmem_shrinker->base);
+	drm_WARN_ON(dev, !list_empty(&shmem_shrinker->lru_evictable.list));
+	drm_WARN_ON(dev, !list_empty(&shmem_shrinker->lru_evicted.list));
+	drm_WARN_ON(dev, !list_empty(&shmem_shrinker->lru_pinned.list));
+	mutex_destroy(&shmem_shrinker->lock);
+}
+
+static int drm_gem_shmem_init(struct drm_device *dev)
+{
+	int err;
+
+	if (drm_WARN_ON(dev, dev->shmem_mm))
+		return -EBUSY;
+
+	dev->shmem_mm = kzalloc(sizeof(*dev->shmem_mm), GFP_KERNEL);
+	if (!dev->shmem_mm)
+		return -ENOMEM;
+
+	err = drm_gem_shmem_shrinker_init(dev->shmem_mm, dev->unique);
+	if (err)
+		goto free_gem_shmem;
+
+	return 0;
+
+free_gem_shmem:
+	kfree(dev->shmem_mm);
+	dev->shmem_mm = NULL;
+
+	return err;
+}
+
+static void drm_gem_shmem_release(struct drm_device *dev, void *ptr)
+{
+	struct drm_gem_shmem *shmem_mm = dev->shmem_mm;
+
+	drm_gem_shmem_shrinker_release(dev, shmem_mm);
+	dev->shmem_mm = NULL;
+	kfree(shmem_mm);
+}
+
+/**
+ * drmm_gem_shmem_init() - Initialize drm-shmem internals
+ * @dev: DRM device
+ *
+ * Cleanup is automatically managed as part of DRM device releasing.
+ * Calling this function multiple times will result in a error.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drmm_gem_shmem_init(struct drm_device *dev)
+{
+	int err;
+
+	err = drm_gem_shmem_init(dev);
+	if (err)
+		return err;
+
+	err = drmm_add_action_or_reset(dev, drm_gem_shmem_release, NULL);
+	if (err)
+		return err;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(drmm_gem_shmem_init);
+
 MODULE_DESCRIPTION("DRM SHMEM memory-management helpers");
 MODULE_IMPORT_NS(DMA_BUF);
 MODULE_LICENSE("GPL v2");
diff --git a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
index 72193bd734e1..1aa94fff7072 100644
--- a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
+++ b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
@@ -15,6 +15,13 @@
 #include "panfrost_gem.h"
 #include "panfrost_mmu.h"
 
+static bool panfrost_gem_shmem_is_purgeable(struct drm_gem_shmem_object *shmem)
+{
+	return (shmem->madv > 0) &&
+		!refcount_read(&shmem->pages_pin_count) && shmem->sgt &&
+		!shmem->base.dma_buf && !shmem->base.import_attach;
+}
+
 static unsigned long
 panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
 {
@@ -27,7 +34,7 @@ panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc
 		return 0;
 
 	list_for_each_entry(shmem, &pfdev->shrinker_list, madv_list) {
-		if (drm_gem_shmem_is_purgeable(shmem))
+		if (panfrost_gem_shmem_is_purgeable(shmem))
 			count += shmem->base.size >> PAGE_SHIFT;
 	}
 
diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
index 7cf4afae2e79..a978f0cb5e84 100644
--- a/include/drm/drm_device.h
+++ b/include/drm/drm_device.h
@@ -16,6 +16,7 @@ struct drm_vblank_crtc;
 struct drm_vma_offset_manager;
 struct drm_vram_mm;
 struct drm_fb_helper;
+struct drm_gem_shmem_shrinker;
 
 struct inode;
 
@@ -290,8 +291,13 @@ struct drm_device {
 	/** @vma_offset_manager: GEM information */
 	struct drm_vma_offset_manager *vma_offset_manager;
 
-	/** @vram_mm: VRAM MM memory manager */
-	struct drm_vram_mm *vram_mm;
+	union {
+		/** @vram_mm: VRAM MM memory manager */
+		struct drm_vram_mm *vram_mm;
+
+		/** @shmem_mm: SHMEM GEM memory manager */
+		struct drm_gem_shmem *shmem_mm;
+	};
 
 	/**
 	 * @switch_power_state:
diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
index 63e91e8f2d5c..65c99da25048 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -6,6 +6,7 @@
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/mutex.h>
+#include <linux/shrinker.h>
 
 #include <drm/drm_file.h>
 #include <drm/drm_gem.h>
@@ -13,6 +14,7 @@
 #include <drm/drm_prime.h>
 
 struct dma_buf_attachment;
+struct drm_device;
 struct drm_mode_create_dumb;
 struct drm_printer;
 struct sg_table;
@@ -53,8 +55,8 @@ struct drm_gem_shmem_object {
 	 * @madv: State for madvise
 	 *
 	 * 0 is active/inuse.
+	 * 1 is not-needed/can-be-purged
 	 * A negative value is the object is purged.
-	 * Positive values are driver specific and not used by the helpers.
 	 */
 	int madv;
 
@@ -115,6 +117,12 @@ struct drm_gem_shmem_object {
 	 * @map_wc: map object write-combined (instead of using shmem defaults).
 	 */
 	bool map_wc : 1;
+
+	/**
+	 * @evicted: True if shmem pages are evicted by the memory shrinker.
+	 * Used internally by memory shrinker.
+	 */
+	bool evicted : 1;
 };
 
 #define to_drm_gem_shmem_obj(obj) \
@@ -133,14 +141,22 @@ void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem,
 int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct *vma);
 
 int drm_gem_shmem_madvise_locked(struct drm_gem_shmem_object *shmem, int madv);
+int drm_gem_shmem_madvise(struct drm_gem_shmem_object *shmem, int madv);
 
 static inline bool drm_gem_shmem_is_purgeable(struct drm_gem_shmem_object *shmem)
 {
-	return (shmem->madv > 0) &&
-		!refcount_read(&shmem->pages_pin_count) && shmem->sgt &&
-		!shmem->base.dma_buf && !shmem->base.import_attach;
+	dma_resv_assert_held(shmem->base.resv);
+
+	return (shmem->madv > 0) && shmem->base.funcs->evict &&
+		refcount_read(&shmem->pages_use_count) &&
+		!refcount_read(&shmem->pages_pin_count) &&
+		!shmem->base.dma_buf && !shmem->base.import_attach &&
+		(shmem->sgt || shmem->evicted);
 }
 
+int drm_gem_shmem_swapin_locked(struct drm_gem_shmem_object *shmem);
+
+void drm_gem_shmem_evict_locked(struct drm_gem_shmem_object *shmem);
 void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem);
 
 struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_shmem_object *shmem);
@@ -284,6 +300,53 @@ static inline int drm_gem_shmem_object_mmap(struct drm_gem_object *obj, struct v
 	return drm_gem_shmem_mmap(shmem, vma);
 }
 
+/**
+ * drm_gem_shmem_object_madvise - unlocked GEM object function for drm_gem_shmem_madvise_locked()
+ * @obj: GEM object
+ * @madv: Madvise value
+ *
+ * This function wraps drm_gem_shmem_madvise_locked(), providing unlocked variant.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+static inline int drm_gem_shmem_object_madvise(struct drm_gem_object *obj, int madv)
+{
+	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
+
+	return drm_gem_shmem_madvise(shmem, madv);
+}
+
+/**
+ * struct drm_gem_shmem_shrinker - Memory shrinker of GEM shmem memory manager
+ */
+struct drm_gem_shmem_shrinker {
+	/** @base: Shrinker for purging shmem GEM objects */
+	struct shrinker base;
+
+	/** @lock: Protects @lru_* */
+	struct mutex lock;
+
+	/** @lru_pinned: List of pinned shmem GEM objects */
+	struct drm_gem_lru lru_pinned;
+
+	/** @lru_evictable: List of shmem GEM objects to be evicted */
+	struct drm_gem_lru lru_evictable;
+
+	/** @lru_evicted: List of evicted shmem GEM objects */
+	struct drm_gem_lru lru_evicted;
+};
+
+/**
+ * struct drm_gem_shmem - GEM shmem memory manager
+ */
+struct drm_gem_shmem {
+	/** @shrinker: GEM shmem shrinker */
+	struct drm_gem_shmem_shrinker shrinker;
+};
+
+int drmm_gem_shmem_init(struct drm_device *dev);
+
 /*
  * Driver ops
  */
-- 
2.41.0

Re: [PATCH v16 15/20] drm/shmem-helper: Add memory shrinker

[Boris Brezillon]

On Sun,  3 Sep 2023 20:07:31 +0300
Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:

> Introduce common drm-shmem shrinker for DRM drivers.
> 
> To start using drm-shmem shrinker drivers should do the following:
> 
> 1. Implement evict() callback of GEM object where driver should check
>    whether object is purgeable or evictable using drm-shmem helpers and
>    perform the shrinking action
> 
> 2. Initialize drm-shmem internals using drmm_gem_shmem_init(drm_device),
>    which will register drm-shmem shrinker
> 
> 3. Implement madvise IOCTL that will use drm_gem_shmem_madvise()
> 
> Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> ---
>  drivers/gpu/drm/drm_gem_shmem_helper.c        | 442 ++++++++++++++++--
>  .../gpu/drm/panfrost/panfrost_gem_shrinker.c  |   9 +-
>  include/drm/drm_device.h                      |  10 +-
>  include/drm/drm_gem_shmem_helper.h            |  71 ++-
>  4 files changed, 494 insertions(+), 38 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index 4633a418faba..a0a6c7e505c8 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -20,6 +20,7 @@
>  #include <drm/drm_device.h>
>  #include <drm/drm_drv.h>
>  #include <drm/drm_gem_shmem_helper.h>
> +#include <drm/drm_managed.h>
>  #include <drm/drm_prime.h>
>  #include <drm/drm_print.h>
>  
> @@ -88,8 +89,6 @@ __drm_gem_shmem_create(struct drm_device *dev, size_t size, bool private)
>  	if (ret)
>  		goto err_release;
>  
> -	INIT_LIST_HEAD(&shmem->madv_list);
> -
>  	if (!private) {
>  		/*
>  		 * Our buffers are kept pinned, so allocating them
> @@ -128,6 +127,62 @@ struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t
>  }
>  EXPORT_SYMBOL_GPL(drm_gem_shmem_create);
>  
> +static bool drm_gem_shmem_is_evictable(struct drm_gem_shmem_object *shmem)
> +{
> +	dma_resv_assert_held(shmem->base.resv);
> +
> +	return (shmem->madv >= 0) && shmem->base.funcs->evict &&
> +		refcount_read(&shmem->pages_use_count) &&
> +		!refcount_read(&shmem->pages_pin_count) &&
> +		!shmem->base.dma_buf && !shmem->base.import_attach &&
> +		shmem->sgt && !shmem->evicted;
> +}
> +
> +static void
> +drm_gem_shmem_update_pages_state_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +	struct drm_gem_shmem *shmem_mm = obj->dev->shmem_mm;
> +	struct drm_gem_shmem_shrinker *shmem_shrinker = &shmem_mm->shrinker;
> +
> +	dma_resv_assert_held(shmem->base.resv);
> +
> +	if (!shmem_shrinker || obj->import_attach)
> +		return;
> +
> +	if (shmem->madv < 0)
> +		drm_gem_lru_remove(&shmem->base);
> +	else if (drm_gem_shmem_is_evictable(shmem) || drm_gem_shmem_is_purgeable(shmem))
> +		drm_gem_lru_move_tail(&shmem_shrinker->lru_evictable, &shmem->base);
> +	else if (shmem->evicted)
> +		drm_gem_lru_move_tail(&shmem_shrinker->lru_evicted, &shmem->base);
> +	else if (!shmem->pages)
> +		drm_gem_lru_remove(&shmem->base);
> +	else
> +		drm_gem_lru_move_tail(&shmem_shrinker->lru_pinned, &shmem->base);
> +}
> +
> +static void
> +drm_gem_shmem_do_release_pages_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +
> +	if (!shmem->pages) {
> +		drm_WARN_ON(obj->dev, !shmem->evicted && shmem->madv >= 0);
> +		return;
> +	}
> +
> +#ifdef CONFIG_X86
> +	if (shmem->map_wc)
> +		set_pages_array_wb(shmem->pages, obj->size >> PAGE_SHIFT);
> +#endif
> +
> +	drm_gem_put_pages(obj, shmem->pages,
> +			  shmem->pages_mark_dirty_on_put,
> +			  shmem->pages_mark_accessed_on_put);
> +	shmem->pages = NULL;
> +}
> +
>  /**
>   * drm_gem_shmem_free - Free resources associated with a shmem GEM object
>   * @shmem: shmem GEM object to free
> @@ -142,8 +197,6 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
>  	if (obj->import_attach) {
>  		drm_prime_gem_destroy(obj, shmem->sgt);
>  	} else if (!shmem->imported_sgt) {
> -		dma_resv_lock(shmem->base.resv, NULL);
> -
>  		drm_WARN_ON(obj->dev, refcount_read(&shmem->vmap_use_count));
>  
>  		if (shmem->sgt) {
> @@ -152,14 +205,27 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
>  			sg_free_table(shmem->sgt);
>  			kfree(shmem->sgt);
>  		}
> -		if (refcount_read(&shmem->pages_use_count)) {
> -			drm_gem_shmem_put_pages_locked(shmem);

It would be preferable to introduce
drm_gem_shmem_do_release_pages_locked() earlier in the series (not a
huge fan of the name BTW, especially since this function can be called
without the lock held in the free path), so we keep things bisectable.

> -			drm_WARN_ON(obj->dev, !shmem->got_pages_sgt);
> +
> +		/*
> +		 * Destroying the object is a special case.. drm_gem_shmem_free()
> +		 * calls many things that WARN_ON if the obj lock is not held.

If that's the case, that should be fixed the same way you're fixing the
put_pages_locked() situation here.

>                * But
> +		 * acquiring the obj lock in drm_gem_shmem_release_pages_locked() can
> +		 * cause a locking order inversion between reservation_ww_class_mutex
> +		 * and fs_reclaim.
> +		 *
> +		 * This deadlock is not actually possible, because no one should
> +		 * be already holding the lock when drm_gem_shmem_free() is called.
> +		 * Unfortunately lockdep is not aware of this detail.  So when the
> +		 * refcount drops to zero, don't touch the reservation lock.
> +		 */
> +		if (shmem->got_pages_sgt &&
> +		    refcount_dec_and_test(&shmem->pages_use_count)) {
> +			drm_gem_shmem_do_release_pages_locked(shmem);
> +			shmem->got_pages_sgt = false;
>  		}

Leaking memory is the right thing to do if pages_use_count > 1 (it's
better to leak than having someone access memory it no longer owns), but
I think it's worth mentioning in the above comment.

>  
>  		drm_WARN_ON(obj->dev, refcount_read(&shmem->pages_use_count));
> -
> -		dma_resv_unlock(shmem->base.resv);
> +		drm_WARN_ON(obj->dev, shmem->got_pages_sgt);
>  	}
>  
>  	drm_gem_object_release(obj);
> @@ -167,15 +233,26 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
>  }
>  EXPORT_SYMBOL_GPL(drm_gem_shmem_free);
>  
> -static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
> +static int
> +drm_gem_shmem_acquire_pages(struct drm_gem_shmem_object *shmem, bool init)
>  {
>  	struct drm_gem_object *obj = &shmem->base;
>  	struct page **pages;
>  
>  	dma_resv_assert_held(shmem->base.resv);

I'd defer this check to the caller (AFAICT, all callers have this
already). This way the function name is consistent with its behavior.

>  
> -	if (refcount_inc_not_zero(&shmem->pages_use_count))
> +	if (shmem->madv < 0) {
> +		drm_WARN_ON(obj->dev, shmem->pages);
> +		return -ENOMEM;
> +	}
> +
> +	if (shmem->pages) {
> +		drm_WARN_ON(obj->dev, !shmem->evicted);
>  		return 0;
> +	}
> +
> +	if (drm_WARN_ON(obj->dev, !(init ^ refcount_read(&shmem->pages_use_count))))
> +		return -EINVAL;
>  
>  	pages = drm_gem_get_pages(obj);
>  	if (IS_ERR(pages)) {
> @@ -196,8 +273,36 @@ static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
>  
>  	shmem->pages = pages;
>  
> +	return 0;
> +}
> +
> +static void
> +drm_gem_shmem_release_pages_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	dma_resv_assert_held(shmem->base.resv);
> +	drm_gem_shmem_do_release_pages_locked(shmem);
> +}

Do we really need an intermediate helper here. Can't we let the callers
ensure the resv is held (that's already the case BTW). This way, you
simply have drm_gem_shmem_{release,acquire}_pages() helpers, and the
drm_gem_shmem_release_pages() helper can be used in
drm_gem_shmem_free().

> +
> +static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	int err;
> +
> +	dma_resv_assert_held(shmem->base.resv);
> +
> +	if (shmem->madv < 0)
> +		return -ENOMEM;
> +
> +	if (refcount_inc_not_zero(&shmem->pages_use_count))
> +		return 0;
> +
> +	err = drm_gem_shmem_acquire_pages(shmem, true);
> +	if (err)
> +		return err;
> +
>  	refcount_set(&shmem->pages_use_count, 1);
>  
> +	drm_gem_shmem_update_pages_state_locked(shmem);
> +
>  	return 0;
>  }
>  
> @@ -209,20 +314,11 @@ static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
>   */
>  void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
>  {
> -	struct drm_gem_object *obj = &shmem->base;
> -
>  	dma_resv_assert_held(shmem->base.resv);
>  
>  	if (refcount_dec_and_test(&shmem->pages_use_count)) {
> -#ifdef CONFIG_X86
> -		if (shmem->map_wc)
> -			set_pages_array_wb(shmem->pages, obj->size >> PAGE_SHIFT);
> -#endif
> -
> -		drm_gem_put_pages(obj, shmem->pages,
> -				  shmem->pages_mark_dirty_on_put,
> -				  shmem->pages_mark_accessed_on_put);
> -		shmem->pages = NULL;
> +		drm_gem_shmem_release_pages_locked(shmem);
> +		drm_gem_shmem_update_pages_state_locked(shmem);
>  	}
>  }
>  EXPORT_SYMBOL_GPL(drm_gem_shmem_put_pages_locked);
> @@ -251,8 +347,15 @@ static int drm_gem_shmem_pin_locked(struct drm_gem_shmem_object *shmem)
>  		return 0;
>  
>  	ret = drm_gem_shmem_get_pages_locked(shmem);
> -	if (!ret)
> +	if (!ret) {
> +		ret = drm_gem_shmem_swapin_locked(shmem);
> +		if (ret) {
> +			drm_gem_shmem_put_pages_locked(shmem);
> +			return ret;
> +		}
> +
>  		refcount_set(&shmem->pages_pin_count, 1);
> +	}
>  
>  	return ret;
>  }
> @@ -448,29 +551,54 @@ int drm_gem_shmem_madvise_locked(struct drm_gem_shmem_object *shmem, int madv)
>  
>  	madv = shmem->madv;
>  
> +	drm_gem_shmem_update_pages_state_locked(shmem);
> +
>  	return (madv >= 0);
>  }
>  EXPORT_SYMBOL_GPL(drm_gem_shmem_madvise_locked);
>  
> -void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem)
> +int drm_gem_shmem_madvise(struct drm_gem_shmem_object *shmem, int madv)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +	int ret;
> +
> +	ret = dma_resv_lock_interruptible(obj->resv, NULL);
> +	if (ret)
> +		return ret;
> +
> +	ret = drm_gem_shmem_madvise_locked(shmem, madv);
> +	dma_resv_unlock(obj->resv);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_madvise);
> +
> +static void drm_gem_shmem_unpin_pages_locked(struct drm_gem_shmem_object *shmem)
>  {
>  	struct drm_gem_object *obj = &shmem->base;
>  	struct drm_device *dev = obj->dev;
>  
>  	dma_resv_assert_held(shmem->base.resv);
>  
> -	drm_WARN_ON(obj->dev, !drm_gem_shmem_is_purgeable(shmem));
> +	if (shmem->evicted)
> +		return;
>  
>  	dma_unmap_sgtable(dev->dev, shmem->sgt, DMA_BIDIRECTIONAL, 0);
> +	drm_gem_shmem_release_pages_locked(shmem);
> +	drm_vma_node_unmap(&obj->vma_node, dev->anon_inode->i_mapping);
> +
>  	sg_free_table(shmem->sgt);
>  	kfree(shmem->sgt);
>  	shmem->sgt = NULL;
> +}
>  
> -	drm_gem_shmem_put_pages_locked(shmem);
> +void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
>  
> -	shmem->madv = -1;
> +	drm_WARN_ON(obj->dev, !drm_gem_shmem_is_purgeable(shmem));
>  
> -	drm_vma_node_unmap(&obj->vma_node, dev->anon_inode->i_mapping);
> +	drm_gem_shmem_unpin_pages_locked(shmem);
>  	drm_gem_free_mmap_offset(obj);
>  
>  	/* Our goal here is to return as much of the memory as
> @@ -481,9 +609,59 @@ void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem)
>  	shmem_truncate_range(file_inode(obj->filp), 0, (loff_t)-1);
>  
>  	invalidate_mapping_pages(file_inode(obj->filp)->i_mapping, 0, (loff_t)-1);
> +
> +	shmem->madv = -1;
> +	shmem->evicted = false;
> +	drm_gem_shmem_update_pages_state_locked(shmem);
>  }
>  EXPORT_SYMBOL_GPL(drm_gem_shmem_purge_locked);
>  
> +/**
> + * drm_gem_shmem_swapin_locked() - Moves shmem GEM back to memory and enables
> + *                                 hardware access to the memory.
> + * @shmem: shmem GEM object
> + *
> + * This function moves shmem GEM back to memory if it was previously evicted
> + * by the memory shrinker. The GEM is ready to use on success.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +int drm_gem_shmem_swapin_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +	struct sg_table *sgt;
> +	int err;
> +
> +	dma_resv_assert_held(shmem->base.resv);
> +
> +	if (shmem->evicted) {
> +		err = drm_gem_shmem_acquire_pages(shmem, false);
> +		if (err)
> +			return err;
> +
> +		sgt = drm_gem_shmem_get_sg_table(shmem);
> +		if (IS_ERR(sgt))
> +			return PTR_ERR(sgt);
> +
> +		err = dma_map_sgtable(obj->dev->dev, sgt,
> +				      DMA_BIDIRECTIONAL, 0);
> +		if (err) {
> +			sg_free_table(sgt);
> +			kfree(sgt);
> +			return err;
> +		}
> +
> +		shmem->sgt = sgt;
> +		shmem->evicted = false;
> +
> +		drm_gem_shmem_update_pages_state_locked(shmem);
> +	}
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_swapin_locked);
> +
>  /**
>   * drm_gem_shmem_dumb_create - Create a dumb shmem buffer object
>   * @file: DRM file structure to create the dumb buffer for
> @@ -530,22 +708,34 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
>  	vm_fault_t ret;
>  	struct page *page;
>  	pgoff_t page_offset;
> +	bool pages_unpinned;
> +	int err;
>  
>  	/* We don't use vmf->pgoff since that has the fake offset */
>  	page_offset = (vmf->address - vma->vm_start) >> PAGE_SHIFT;
>  
>  	dma_resv_lock(shmem->base.resv, NULL);
>  
> -	if (page_offset >= num_pages ||
> -	    drm_WARN_ON_ONCE(obj->dev, !shmem->pages) ||
> -	    shmem->madv < 0) {
> +	/* Sanity-check that we have the pages pointer when it should present */
> +	pages_unpinned = (shmem->evicted || shmem->madv < 0 ||
> +			  !refcount_read(&shmem->pages_use_count));
> +	drm_WARN_ON_ONCE(obj->dev, !shmem->pages ^ pages_unpinned);
> +
> +	if (page_offset >= num_pages || (!shmem->pages && !shmem->evicted)) {
>  		ret = VM_FAULT_SIGBUS;
>  	} else {
> +		err = drm_gem_shmem_swapin_locked(shmem);
> +		if (err) {
> +			ret = VM_FAULT_OOM;
> +			goto unlock;
> +		}
> +
>  		page = shmem->pages[page_offset];
>  
>  		ret = vmf_insert_pfn(vma, vmf->address, page_to_pfn(page));
>  	}
>  
> +unlock:
>  	dma_resv_unlock(shmem->base.resv);
>  
>  	return ret;
> @@ -568,6 +758,7 @@ static void drm_gem_shmem_vm_open(struct vm_area_struct *vma)
>  	drm_WARN_ON_ONCE(obj->dev,
>  			 !refcount_inc_not_zero(&shmem->pages_use_count));
>  
> +	drm_gem_shmem_update_pages_state_locked(shmem);
>  	dma_resv_unlock(shmem->base.resv);
>  
>  	drm_gem_vm_open(vma);
> @@ -653,7 +844,9 @@ void drm_gem_shmem_print_info(const struct drm_gem_shmem_object *shmem,
>  	drm_printf_indent(p, indent, "pages_pin_count=%u\n", refcount_read(&shmem->pages_pin_count));
>  	drm_printf_indent(p, indent, "pages_use_count=%u\n", refcount_read(&shmem->pages_use_count));
>  	drm_printf_indent(p, indent, "vmap_use_count=%u\n", refcount_read(&shmem->vmap_use_count));
> +	drm_printf_indent(p, indent, "evicted=%d\n", shmem->evicted);
>  	drm_printf_indent(p, indent, "vaddr=%p\n", shmem->vaddr);
> +	drm_printf_indent(p, indent, "madv=%d\n", shmem->madv);
>  }
>  EXPORT_SYMBOL_GPL(drm_gem_shmem_print_info);
>  
> @@ -715,6 +908,8 @@ static struct sg_table *drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_
>  
>  	shmem->sgt = sgt;
>  
> +	drm_gem_shmem_update_pages_state_locked(shmem);
> +
>  	return sgt;
>  
>  err_free_sgt:
> @@ -802,6 +997,191 @@ drm_gem_shmem_prime_import_sg_table(struct drm_device *dev,
>  }
>  EXPORT_SYMBOL_GPL(drm_gem_shmem_prime_import_sg_table);
>  
> +static struct drm_gem_shmem_shrinker *
> +to_drm_gem_shmem_shrinker(struct shrinker *shrinker)
> +{
> +	return container_of(shrinker, struct drm_gem_shmem_shrinker, base);
> +}
> +
> +static unsigned long
> +drm_gem_shmem_shrinker_count_objects(struct shrinker *shrinker,
> +				     struct shrink_control *sc)
> +{
> +	struct drm_gem_shmem_shrinker *shmem_shrinker =
> +					to_drm_gem_shmem_shrinker(shrinker);
> +	unsigned long count = shmem_shrinker->lru_evictable.count;
> +
> +	if (count >= SHRINK_EMPTY)
> +		return SHRINK_EMPTY - 1;
> +
> +	return count ?: SHRINK_EMPTY;
> +}
> +
> +void drm_gem_shmem_evict_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +
> +	drm_WARN_ON(obj->dev, !drm_gem_shmem_is_evictable(shmem));
> +	drm_WARN_ON(obj->dev, shmem->evicted);
> +
> +	drm_gem_shmem_unpin_pages_locked(shmem);
> +
> +	shmem->evicted = true;
> +	drm_gem_shmem_update_pages_state_locked(shmem);
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_evict_locked);
> +
> +static bool drm_gem_shmem_shrinker_evict_locked(struct drm_gem_object *obj)
> +{
> +	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> +	int err;
> +
> +	if (!drm_gem_shmem_is_evictable(shmem) ||
> +	    get_nr_swap_pages() < obj->size >> PAGE_SHIFT)
> +		return false;
> +
> +	err = drm_gem_evict_locked(obj);
> +	if (err)
> +		return false;
> +
> +	return true;
> +}
> +
> +static bool drm_gem_shmem_shrinker_purge_locked(struct drm_gem_object *obj)
> +{
> +	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> +	int err;
> +
> +	if (!drm_gem_shmem_is_purgeable(shmem))
> +		return false;
> +
> +	err = drm_gem_evict_locked(obj);
> +	if (err)
> +		return false;
> +
> +	return true;
> +}
> +
> +static unsigned long
> +drm_gem_shmem_shrinker_scan_objects(struct shrinker *shrinker,
> +				    struct shrink_control *sc)
> +{
> +	struct drm_gem_shmem_shrinker *shmem_shrinker;
> +	unsigned long nr_to_scan = sc->nr_to_scan;
> +	unsigned long remaining = 0;
> +	unsigned long freed = 0;
> +
> +	shmem_shrinker = to_drm_gem_shmem_shrinker(shrinker);
> +
> +	/* purge as many objects as we can */
> +	freed += drm_gem_lru_scan(&shmem_shrinker->lru_evictable,
> +				  nr_to_scan, &remaining,
> +				  drm_gem_shmem_shrinker_purge_locked);
> +
> +	/* evict as many objects as we can */
> +	if (freed < nr_to_scan)
> +		freed += drm_gem_lru_scan(&shmem_shrinker->lru_evictable,
> +					  nr_to_scan - freed, &remaining,
> +					  drm_gem_shmem_shrinker_evict_locked);
> +
> +	return (freed > 0 && remaining > 0) ? freed : SHRINK_STOP;
> +}
> +
> +static int drm_gem_shmem_shrinker_init(struct drm_gem_shmem *shmem_mm,
> +				       const char *shrinker_name)
> +{
> +	struct drm_gem_shmem_shrinker *shmem_shrinker = &shmem_mm->shrinker;
> +	int err;
> +
> +	shmem_shrinker->base.count_objects = drm_gem_shmem_shrinker_count_objects;
> +	shmem_shrinker->base.scan_objects = drm_gem_shmem_shrinker_scan_objects;
> +	shmem_shrinker->base.seeks = DEFAULT_SEEKS;
> +
> +	mutex_init(&shmem_shrinker->lock);
> +	drm_gem_lru_init(&shmem_shrinker->lru_evictable, &shmem_shrinker->lock);
> +	drm_gem_lru_init(&shmem_shrinker->lru_evicted, &shmem_shrinker->lock);
> +	drm_gem_lru_init(&shmem_shrinker->lru_pinned, &shmem_shrinker->lock);
> +
> +	err = register_shrinker(&shmem_shrinker->base, shrinker_name);
> +	if (err) {
> +		mutex_destroy(&shmem_shrinker->lock);
> +		return err;
> +	}
> +
> +	return 0;
> +}
> +
> +static void drm_gem_shmem_shrinker_release(struct drm_device *dev,
> +					   struct drm_gem_shmem *shmem_mm)
> +{
> +	struct drm_gem_shmem_shrinker *shmem_shrinker = &shmem_mm->shrinker;
> +
> +	unregister_shrinker(&shmem_shrinker->base);
> +	drm_WARN_ON(dev, !list_empty(&shmem_shrinker->lru_evictable.list));
> +	drm_WARN_ON(dev, !list_empty(&shmem_shrinker->lru_evicted.list));
> +	drm_WARN_ON(dev, !list_empty(&shmem_shrinker->lru_pinned.list));
> +	mutex_destroy(&shmem_shrinker->lock);
> +}
> +
> +static int drm_gem_shmem_init(struct drm_device *dev)
> +{
> +	int err;
> +
> +	if (drm_WARN_ON(dev, dev->shmem_mm))
> +		return -EBUSY;
> +
> +	dev->shmem_mm = kzalloc(sizeof(*dev->shmem_mm), GFP_KERNEL);
> +	if (!dev->shmem_mm)
> +		return -ENOMEM;
> +
> +	err = drm_gem_shmem_shrinker_init(dev->shmem_mm, dev->unique);
> +	if (err)
> +		goto free_gem_shmem;
> +
> +	return 0;
> +
> +free_gem_shmem:
> +	kfree(dev->shmem_mm);
> +	dev->shmem_mm = NULL;
> +
> +	return err;
> +}
> +
> +static void drm_gem_shmem_release(struct drm_device *dev, void *ptr)
> +{
> +	struct drm_gem_shmem *shmem_mm = dev->shmem_mm;
> +
> +	drm_gem_shmem_shrinker_release(dev, shmem_mm);
> +	dev->shmem_mm = NULL;
> +	kfree(shmem_mm);
> +}
> +
> +/**
> + * drmm_gem_shmem_init() - Initialize drm-shmem internals
> + * @dev: DRM device
> + *
> + * Cleanup is automatically managed as part of DRM device releasing.
> + * Calling this function multiple times will result in a error.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +int drmm_gem_shmem_init(struct drm_device *dev)
> +{
> +	int err;
> +
> +	err = drm_gem_shmem_init(dev);
> +	if (err)
> +		return err;
> +
> +	err = drmm_add_action_or_reset(dev, drm_gem_shmem_release, NULL);
> +	if (err)
> +		return err;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(drmm_gem_shmem_init);
> +
>  MODULE_DESCRIPTION("DRM SHMEM memory-management helpers");
>  MODULE_IMPORT_NS(DMA_BUF);
>  MODULE_LICENSE("GPL v2");
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
> index 72193bd734e1..1aa94fff7072 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
> @@ -15,6 +15,13 @@
>  #include "panfrost_gem.h"
>  #include "panfrost_mmu.h"
>  
> +static bool panfrost_gem_shmem_is_purgeable(struct drm_gem_shmem_object *shmem)
> +{
> +	return (shmem->madv > 0) &&
> +		!refcount_read(&shmem->pages_pin_count) && shmem->sgt &&
> +		!shmem->base.dma_buf && !shmem->base.import_attach;
> +}
> +
>  static unsigned long
>  panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
>  {
> @@ -27,7 +34,7 @@ panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc
>  		return 0;
>  
>  	list_for_each_entry(shmem, &pfdev->shrinker_list, madv_list) {
> -		if (drm_gem_shmem_is_purgeable(shmem))
> +		if (panfrost_gem_shmem_is_purgeable(shmem))
>  			count += shmem->base.size >> PAGE_SHIFT;
>  	}
>  
> diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
> index 7cf4afae2e79..a978f0cb5e84 100644
> --- a/include/drm/drm_device.h
> +++ b/include/drm/drm_device.h
> @@ -16,6 +16,7 @@ struct drm_vblank_crtc;
>  struct drm_vma_offset_manager;
>  struct drm_vram_mm;
>  struct drm_fb_helper;
> +struct drm_gem_shmem_shrinker;
>  
>  struct inode;
>  
> @@ -290,8 +291,13 @@ struct drm_device {
>  	/** @vma_offset_manager: GEM information */
>  	struct drm_vma_offset_manager *vma_offset_manager;
>  
> -	/** @vram_mm: VRAM MM memory manager */
> -	struct drm_vram_mm *vram_mm;
> +	union {
> +		/** @vram_mm: VRAM MM memory manager */
> +		struct drm_vram_mm *vram_mm;
> +
> +		/** @shmem_mm: SHMEM GEM memory manager */
> +		struct drm_gem_shmem *shmem_mm;
> +	};
>  
>  	/**
>  	 * @switch_power_state:
> diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
> index 63e91e8f2d5c..65c99da25048 100644
> --- a/include/drm/drm_gem_shmem_helper.h
> +++ b/include/drm/drm_gem_shmem_helper.h
> @@ -6,6 +6,7 @@
>  #include <linux/fs.h>
>  #include <linux/mm.h>
>  #include <linux/mutex.h>
> +#include <linux/shrinker.h>
>  
>  #include <drm/drm_file.h>
>  #include <drm/drm_gem.h>
> @@ -13,6 +14,7 @@
>  #include <drm/drm_prime.h>
>  
>  struct dma_buf_attachment;
> +struct drm_device;
>  struct drm_mode_create_dumb;
>  struct drm_printer;
>  struct sg_table;
> @@ -53,8 +55,8 @@ struct drm_gem_shmem_object {
>  	 * @madv: State for madvise
>  	 *
>  	 * 0 is active/inuse.
> +	 * 1 is not-needed/can-be-purged
>  	 * A negative value is the object is purged.
> -	 * Positive values are driver specific and not used by the helpers.
>  	 */
>  	int madv;
>  
> @@ -115,6 +117,12 @@ struct drm_gem_shmem_object {
>  	 * @map_wc: map object write-combined (instead of using shmem defaults).
>  	 */
>  	bool map_wc : 1;
> +
> +	/**
> +	 * @evicted: True if shmem pages are evicted by the memory shrinker.
> +	 * Used internally by memory shrinker.
> +	 */
> +	bool evicted : 1;
>  };
>  
>  #define to_drm_gem_shmem_obj(obj) \
> @@ -133,14 +141,22 @@ void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem,
>  int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct *vma);
>  
>  int drm_gem_shmem_madvise_locked(struct drm_gem_shmem_object *shmem, int madv);
> +int drm_gem_shmem_madvise(struct drm_gem_shmem_object *shmem, int madv);
>  
>  static inline bool drm_gem_shmem_is_purgeable(struct drm_gem_shmem_object *shmem)
>  {
> -	return (shmem->madv > 0) &&
> -		!refcount_read(&shmem->pages_pin_count) && shmem->sgt &&
> -		!shmem->base.dma_buf && !shmem->base.import_attach;
> +	dma_resv_assert_held(shmem->base.resv);
> +
> +	return (shmem->madv > 0) && shmem->base.funcs->evict &&
> +		refcount_read(&shmem->pages_use_count) &&
> +		!refcount_read(&shmem->pages_pin_count) &&
> +		!shmem->base.dma_buf && !shmem->base.import_attach &&
> +		(shmem->sgt || shmem->evicted);
>  }
>  
> +int drm_gem_shmem_swapin_locked(struct drm_gem_shmem_object *shmem);
> +
> +void drm_gem_shmem_evict_locked(struct drm_gem_shmem_object *shmem);
>  void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem);
>  
>  struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_shmem_object *shmem);
> @@ -284,6 +300,53 @@ static inline int drm_gem_shmem_object_mmap(struct drm_gem_object *obj, struct v
>  	return drm_gem_shmem_mmap(shmem, vma);
>  }
>  
> +/**
> + * drm_gem_shmem_object_madvise - unlocked GEM object function for drm_gem_shmem_madvise_locked()
> + * @obj: GEM object
> + * @madv: Madvise value
> + *
> + * This function wraps drm_gem_shmem_madvise_locked(), providing unlocked variant.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +static inline int drm_gem_shmem_object_madvise(struct drm_gem_object *obj, int madv)
> +{
> +	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> +
> +	return drm_gem_shmem_madvise(shmem, madv);
> +}
> +
> +/**
> + * struct drm_gem_shmem_shrinker - Memory shrinker of GEM shmem memory manager
> + */
> +struct drm_gem_shmem_shrinker {
> +	/** @base: Shrinker for purging shmem GEM objects */
> +	struct shrinker base;
> +
> +	/** @lock: Protects @lru_* */
> +	struct mutex lock;
> +
> +	/** @lru_pinned: List of pinned shmem GEM objects */
> +	struct drm_gem_lru lru_pinned;
> +
> +	/** @lru_evictable: List of shmem GEM objects to be evicted */
> +	struct drm_gem_lru lru_evictable;
> +
> +	/** @lru_evicted: List of evicted shmem GEM objects */
> +	struct drm_gem_lru lru_evicted;
> +};
> +
> +/**
> + * struct drm_gem_shmem - GEM shmem memory manager
> + */
> +struct drm_gem_shmem {
> +	/** @shrinker: GEM shmem shrinker */
> +	struct drm_gem_shmem_shrinker shrinker;
> +};
> +
> +int drmm_gem_shmem_init(struct drm_device *dev);
> +
>  /*
>   * Driver ops
>   */

Re: [PATCH v16 15/20] drm/shmem-helper: Add memory shrinker

[Dmitry Osipenko]

On 9/5/23 11:03, Boris Brezillon wrote:
>>                * But
>> +		 * acquiring the obj lock in drm_gem_shmem_release_pages_locked() can
>> +		 * cause a locking order inversion between reservation_ww_class_mutex
>> +		 * and fs_reclaim.
>> +		 *
>> +		 * This deadlock is not actually possible, because no one should
>> +		 * be already holding the lock when drm_gem_shmem_free() is called.
>> +		 * Unfortunately lockdep is not aware of this detail.  So when the
>> +		 * refcount drops to zero, don't touch the reservation lock.
>> +		 */
>> +		if (shmem->got_pages_sgt &&
>> +		    refcount_dec_and_test(&shmem->pages_use_count)) {
>> +			drm_gem_shmem_do_release_pages_locked(shmem);
>> +			shmem->got_pages_sgt = false;
>>  		}
> Leaking memory is the right thing to do if pages_use_count > 1 (it's
> better to leak than having someone access memory it no longer owns), but
> I think it's worth mentioning in the above comment.

It's unlikely that it will be only a leak without a following up
use-after-free. Neither is acceptable.

The drm_gem_shmem_free() could be changed such that kernel won't blow up
on a refcnt bug, but that's not worthwhile doing because drivers
shouldn't have silly bugs.

-- 
Best regards,
Dmitry

Re: [PATCH v16 15/20] drm/shmem-helper: Add memory shrinker

[Boris Brezillon]

On Wed, 13 Sep 2023 03:56:14 +0300
Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:

> On 9/5/23 11:03, Boris Brezillon wrote:
> >>                * But
> >> +		 * acquiring the obj lock in drm_gem_shmem_release_pages_locked() can
> >> +		 * cause a locking order inversion between reservation_ww_class_mutex
> >> +		 * and fs_reclaim.
> >> +		 *
> >> +		 * This deadlock is not actually possible, because no one should
> >> +		 * be already holding the lock when drm_gem_shmem_free() is called.
> >> +		 * Unfortunately lockdep is not aware of this detail.  So when the
> >> +		 * refcount drops to zero, don't touch the reservation lock.
> >> +		 */
> >> +		if (shmem->got_pages_sgt &&
> >> +		    refcount_dec_and_test(&shmem->pages_use_count)) {
> >> +			drm_gem_shmem_do_release_pages_locked(shmem);
> >> +			shmem->got_pages_sgt = false;
> >>  		}  
> > Leaking memory is the right thing to do if pages_use_count > 1 (it's
> > better to leak than having someone access memory it no longer owns), but
> > I think it's worth mentioning in the above comment.  
> 
> It's unlikely that it will be only a leak without a following up
> use-after-free. Neither is acceptable.

Not necessarily, if you have a page leak, it could be that the GPU has
access to those pages, but doesn't need the GEM object anymore
(pages are mapped by the iommu, which doesn't need shmem->sgt or
shmem->pages after the mapping is created). Without a WARN_ON(), this
can go unnoticed and lead to memory corruptions/information leaks.

> 
> The drm_gem_shmem_free() could be changed such that kernel won't blow up
> on a refcnt bug, but that's not worthwhile doing because drivers
> shouldn't have silly bugs.

We definitely don't want to fix that, but we want to complain loudly
(WARN_ON()), and make sure the risk is limited (preventing memory from
being re-assigned to someone else by not freeing it).

Re: [PATCH v16 15/20] drm/shmem-helper: Add memory shrinker

[Dmitry Osipenko]

On 9/13/23 10:48, Boris Brezillon wrote:
> On Wed, 13 Sep 2023 03:56:14 +0300
> Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
> 
>> On 9/5/23 11:03, Boris Brezillon wrote:
>>>>                * But
>>>> +		 * acquiring the obj lock in drm_gem_shmem_release_pages_locked() can
>>>> +		 * cause a locking order inversion between reservation_ww_class_mutex
>>>> +		 * and fs_reclaim.
>>>> +		 *
>>>> +		 * This deadlock is not actually possible, because no one should
>>>> +		 * be already holding the lock when drm_gem_shmem_free() is called.
>>>> +		 * Unfortunately lockdep is not aware of this detail.  So when the
>>>> +		 * refcount drops to zero, don't touch the reservation lock.
>>>> +		 */
>>>> +		if (shmem->got_pages_sgt &&
>>>> +		    refcount_dec_and_test(&shmem->pages_use_count)) {
>>>> +			drm_gem_shmem_do_release_pages_locked(shmem);
>>>> +			shmem->got_pages_sgt = false;
>>>>  		}  
>>> Leaking memory is the right thing to do if pages_use_count > 1 (it's
>>> better to leak than having someone access memory it no longer owns), but
>>> I think it's worth mentioning in the above comment.  
>>
>> It's unlikely that it will be only a leak without a following up
>> use-after-free. Neither is acceptable.
> 
> Not necessarily, if you have a page leak, it could be that the GPU has
> access to those pages, but doesn't need the GEM object anymore
> (pages are mapped by the iommu, which doesn't need shmem->sgt or
> shmem->pages after the mapping is created). Without a WARN_ON(), this
> can go unnoticed and lead to memory corruptions/information leaks.
> 
>>
>> The drm_gem_shmem_free() could be changed such that kernel won't blow up
>> on a refcnt bug, but that's not worthwhile doing because drivers
>> shouldn't have silly bugs.
> 
> We definitely don't want to fix that, but we want to complain loudly
> (WARN_ON()), and make sure the risk is limited (preventing memory from
> being re-assigned to someone else by not freeing it).

That's what the code did and continues to do here. Not exactly sure what
you're trying to say. I'm going to relocate the comment in v17 to
put_pages(), we can continue discussing it there if I'm missing yours point.

-- 
Best regards,
Dmitry

Re: [PATCH v16 15/20] drm/shmem-helper: Add memory shrinker

[Boris Brezillon]

On Thu, 14 Sep 2023 07:02:52 +0300
Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:

> On 9/13/23 10:48, Boris Brezillon wrote:
> > On Wed, 13 Sep 2023 03:56:14 +0300
> > Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
> >   
> >> On 9/5/23 11:03, Boris Brezillon wrote:  
> >>>>                * But
> >>>> +		 * acquiring the obj lock in drm_gem_shmem_release_pages_locked() can
> >>>> +		 * cause a locking order inversion between reservation_ww_class_mutex
> >>>> +		 * and fs_reclaim.
> >>>> +		 *
> >>>> +		 * This deadlock is not actually possible, because no one should
> >>>> +		 * be already holding the lock when drm_gem_shmem_free() is called.
> >>>> +		 * Unfortunately lockdep is not aware of this detail.  So when the
> >>>> +		 * refcount drops to zero, don't touch the reservation lock.
> >>>> +		 */
> >>>> +		if (shmem->got_pages_sgt &&
> >>>> +		    refcount_dec_and_test(&shmem->pages_use_count)) {
> >>>> +			drm_gem_shmem_do_release_pages_locked(shmem);
> >>>> +			shmem->got_pages_sgt = false;
> >>>>  		}    
> >>> Leaking memory is the right thing to do if pages_use_count > 1 (it's
> >>> better to leak than having someone access memory it no longer owns), but
> >>> I think it's worth mentioning in the above comment.    
> >>
> >> It's unlikely that it will be only a leak without a following up
> >> use-after-free. Neither is acceptable.  
> > 
> > Not necessarily, if you have a page leak, it could be that the GPU has
> > access to those pages, but doesn't need the GEM object anymore
> > (pages are mapped by the iommu, which doesn't need shmem->sgt or
> > shmem->pages after the mapping is created). Without a WARN_ON(), this
> > can go unnoticed and lead to memory corruptions/information leaks.
> >   
> >>
> >> The drm_gem_shmem_free() could be changed such that kernel won't blow up
> >> on a refcnt bug, but that's not worthwhile doing because drivers
> >> shouldn't have silly bugs.  
> > 
> > We definitely don't want to fix that, but we want to complain loudly
> > (WARN_ON()), and make sure the risk is limited (preventing memory from
> > being re-assigned to someone else by not freeing it).  
> 
> That's what the code did and continues to do here. Not exactly sure what
> you're trying to say. I'm going to relocate the comment in v17 to
> put_pages(), we can continue discussing it there if I'm missing yours point.
> 

I'm just saying it would be worth mentioning that we're intentionally
leaking memory if shmem->pages_use_count > 1. Something like:

	/**
	 * shmem->pages_use_count should be 1 when ->sgt != NULL and
	 * zero otherwise. If some users still hold a pages reference
	 * that's a bug, and we intentionally leak the pages so they
	 * can't be re-allocated to someone else while the GPU/CPU
	 * still have access to it.
	 */
	drm_WARN_ON(drm,
		    refcount_read(&shmem->pages_use_count) == (shmem->sgt ? 1 : 0));
	if (shmem->sgt && refcount_dec_and_test(&shmem->pages_use_count))
		drm_gem_shmem_free_pages(shmem);

Re: [PATCH v16 15/20] drm/shmem-helper: Add memory shrinker

[Dmitry Osipenko]

On 9/14/23 10:36, Boris Brezillon wrote:
> On Thu, 14 Sep 2023 07:02:52 +0300
> Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
> 
>> On 9/13/23 10:48, Boris Brezillon wrote:
>>> On Wed, 13 Sep 2023 03:56:14 +0300
>>> Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
>>>   
>>>> On 9/5/23 11:03, Boris Brezillon wrote:  
>>>>>>                * But
>>>>>> +		 * acquiring the obj lock in drm_gem_shmem_release_pages_locked() can
>>>>>> +		 * cause a locking order inversion between reservation_ww_class_mutex
>>>>>> +		 * and fs_reclaim.
>>>>>> +		 *
>>>>>> +		 * This deadlock is not actually possible, because no one should
>>>>>> +		 * be already holding the lock when drm_gem_shmem_free() is called.
>>>>>> +		 * Unfortunately lockdep is not aware of this detail.  So when the
>>>>>> +		 * refcount drops to zero, don't touch the reservation lock.
>>>>>> +		 */
>>>>>> +		if (shmem->got_pages_sgt &&
>>>>>> +		    refcount_dec_and_test(&shmem->pages_use_count)) {
>>>>>> +			drm_gem_shmem_do_release_pages_locked(shmem);
>>>>>> +			shmem->got_pages_sgt = false;
>>>>>>  		}    
>>>>> Leaking memory is the right thing to do if pages_use_count > 1 (it's
>>>>> better to leak than having someone access memory it no longer owns), but
>>>>> I think it's worth mentioning in the above comment.    
>>>>
>>>> It's unlikely that it will be only a leak without a following up
>>>> use-after-free. Neither is acceptable.  
>>>
>>> Not necessarily, if you have a page leak, it could be that the GPU has
>>> access to those pages, but doesn't need the GEM object anymore
>>> (pages are mapped by the iommu, which doesn't need shmem->sgt or
>>> shmem->pages after the mapping is created). Without a WARN_ON(), this
>>> can go unnoticed and lead to memory corruptions/information leaks.
>>>   
>>>>
>>>> The drm_gem_shmem_free() could be changed such that kernel won't blow up
>>>> on a refcnt bug, but that's not worthwhile doing because drivers
>>>> shouldn't have silly bugs.  
>>>
>>> We definitely don't want to fix that, but we want to complain loudly
>>> (WARN_ON()), and make sure the risk is limited (preventing memory from
>>> being re-assigned to someone else by not freeing it).  
>>
>> That's what the code did and continues to do here. Not exactly sure what
>> you're trying to say. I'm going to relocate the comment in v17 to
>> put_pages(), we can continue discussing it there if I'm missing yours point.
>>
> 
> I'm just saying it would be worth mentioning that we're intentionally
> leaking memory if shmem->pages_use_count > 1. Something like:
> 
> 	/**
> 	 * shmem->pages_use_count should be 1 when ->sgt != NULL and
> 	 * zero otherwise. If some users still hold a pages reference
> 	 * that's a bug, and we intentionally leak the pages so they
> 	 * can't be re-allocated to someone else while the GPU/CPU
> 	 * still have access to it.
> 	 */
> 	drm_WARN_ON(drm,
> 		    refcount_read(&shmem->pages_use_count) == (shmem->sgt ? 1 : 0));
> 	if (shmem->sgt && refcount_dec_and_test(&shmem->pages_use_count))
> 		drm_gem_shmem_free_pages(shmem);

That may be acceptable, but only once there will a driver using this
feature.

-- 
Best regards,
Dmitry

Re: [PATCH v16 15/20] drm/shmem-helper: Add memory shrinker

[Boris Brezillon]

On Thu, 14 Sep 2023 10:50:32 +0300
Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:

> On 9/14/23 10:36, Boris Brezillon wrote:
> > On Thu, 14 Sep 2023 07:02:52 +0300
> > Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
> >   
> >> On 9/13/23 10:48, Boris Brezillon wrote:  
> >>> On Wed, 13 Sep 2023 03:56:14 +0300
> >>> Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
> >>>     
> >>>> On 9/5/23 11:03, Boris Brezillon wrote:    
> >>>>>>                * But
> >>>>>> +		 * acquiring the obj lock in drm_gem_shmem_release_pages_locked() can
> >>>>>> +		 * cause a locking order inversion between reservation_ww_class_mutex
> >>>>>> +		 * and fs_reclaim.
> >>>>>> +		 *
> >>>>>> +		 * This deadlock is not actually possible, because no one should
> >>>>>> +		 * be already holding the lock when drm_gem_shmem_free() is called.
> >>>>>> +		 * Unfortunately lockdep is not aware of this detail.  So when the
> >>>>>> +		 * refcount drops to zero, don't touch the reservation lock.
> >>>>>> +		 */
> >>>>>> +		if (shmem->got_pages_sgt &&
> >>>>>> +		    refcount_dec_and_test(&shmem->pages_use_count)) {
> >>>>>> +			drm_gem_shmem_do_release_pages_locked(shmem);
> >>>>>> +			shmem->got_pages_sgt = false;
> >>>>>>  		}      
> >>>>> Leaking memory is the right thing to do if pages_use_count > 1 (it's
> >>>>> better to leak than having someone access memory it no longer owns), but
> >>>>> I think it's worth mentioning in the above comment.      
> >>>>
> >>>> It's unlikely that it will be only a leak without a following up
> >>>> use-after-free. Neither is acceptable.    
> >>>
> >>> Not necessarily, if you have a page leak, it could be that the GPU has
> >>> access to those pages, but doesn't need the GEM object anymore
> >>> (pages are mapped by the iommu, which doesn't need shmem->sgt or
> >>> shmem->pages after the mapping is created). Without a WARN_ON(), this
> >>> can go unnoticed and lead to memory corruptions/information leaks.
> >>>     
> >>>>
> >>>> The drm_gem_shmem_free() could be changed such that kernel won't blow up
> >>>> on a refcnt bug, but that's not worthwhile doing because drivers
> >>>> shouldn't have silly bugs.    
> >>>
> >>> We definitely don't want to fix that, but we want to complain loudly
> >>> (WARN_ON()), and make sure the risk is limited (preventing memory from
> >>> being re-assigned to someone else by not freeing it).    
> >>
> >> That's what the code did and continues to do here. Not exactly sure what
> >> you're trying to say. I'm going to relocate the comment in v17 to
> >> put_pages(), we can continue discussing it there if I'm missing yours point.
> >>  
> > 
> > I'm just saying it would be worth mentioning that we're intentionally
> > leaking memory if shmem->pages_use_count > 1. Something like:
> > 
> > 	/**
> > 	 * shmem->pages_use_count should be 1 when ->sgt != NULL and
> > 	 * zero otherwise. If some users still hold a pages reference
> > 	 * that's a bug, and we intentionally leak the pages so they
> > 	 * can't be re-allocated to someone else while the GPU/CPU
> > 	 * still have access to it.
> > 	 */
> > 	drm_WARN_ON(drm,
> > 		    refcount_read(&shmem->pages_use_count) == (shmem->sgt ? 1 : 0));
> > 	if (shmem->sgt && refcount_dec_and_test(&shmem->pages_use_count))
> > 		drm_gem_shmem_free_pages(shmem);  
> 
> That may be acceptable, but only once there will a driver using this
> feature.

Which feature? That's not related to a specific feature, that's just
how drm_gem_shmem_get_pages_sgt() works, it takes a pages ref that can
only be released in drm_gem_shmem_free(), because sgt users are not
refcounted and the sgt stays around until the GEM object is freed or
its pages are evicted. The only valid cases we have at the moment are:

- pages_use_count == 1 && sgt != NULL
- pages_use_count == 0

any other situations are buggy.

Re: [PATCH v16 15/20] drm/shmem-helper: Add memory shrinker

[Dmitry Osipenko]

On 9/14/23 11:27, Boris Brezillon wrote:
> On Thu, 14 Sep 2023 10:50:32 +0300
> Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
> 
>> On 9/14/23 10:36, Boris Brezillon wrote:
>>> On Thu, 14 Sep 2023 07:02:52 +0300
>>> Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
>>>   
>>>> On 9/13/23 10:48, Boris Brezillon wrote:  
>>>>> On Wed, 13 Sep 2023 03:56:14 +0300
>>>>> Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
>>>>>     
>>>>>> On 9/5/23 11:03, Boris Brezillon wrote:    
>>>>>>>>                * But
>>>>>>>> +		 * acquiring the obj lock in drm_gem_shmem_release_pages_locked() can
>>>>>>>> +		 * cause a locking order inversion between reservation_ww_class_mutex
>>>>>>>> +		 * and fs_reclaim.
>>>>>>>> +		 *
>>>>>>>> +		 * This deadlock is not actually possible, because no one should
>>>>>>>> +		 * be already holding the lock when drm_gem_shmem_free() is called.
>>>>>>>> +		 * Unfortunately lockdep is not aware of this detail.  So when the
>>>>>>>> +		 * refcount drops to zero, don't touch the reservation lock.
>>>>>>>> +		 */
>>>>>>>> +		if (shmem->got_pages_sgt &&
>>>>>>>> +		    refcount_dec_and_test(&shmem->pages_use_count)) {
>>>>>>>> +			drm_gem_shmem_do_release_pages_locked(shmem);
>>>>>>>> +			shmem->got_pages_sgt = false;
>>>>>>>>  		}      
>>>>>>> Leaking memory is the right thing to do if pages_use_count > 1 (it's
>>>>>>> better to leak than having someone access memory it no longer owns), but
>>>>>>> I think it's worth mentioning in the above comment.      
>>>>>>
>>>>>> It's unlikely that it will be only a leak without a following up
>>>>>> use-after-free. Neither is acceptable.    
>>>>>
>>>>> Not necessarily, if you have a page leak, it could be that the GPU has
>>>>> access to those pages, but doesn't need the GEM object anymore
>>>>> (pages are mapped by the iommu, which doesn't need shmem->sgt or
>>>>> shmem->pages after the mapping is created). Without a WARN_ON(), this
>>>>> can go unnoticed and lead to memory corruptions/information leaks.
>>>>>     
>>>>>>
>>>>>> The drm_gem_shmem_free() could be changed such that kernel won't blow up
>>>>>> on a refcnt bug, but that's not worthwhile doing because drivers
>>>>>> shouldn't have silly bugs.    
>>>>>
>>>>> We definitely don't want to fix that, but we want to complain loudly
>>>>> (WARN_ON()), and make sure the risk is limited (preventing memory from
>>>>> being re-assigned to someone else by not freeing it).    
>>>>
>>>> That's what the code did and continues to do here. Not exactly sure what
>>>> you're trying to say. I'm going to relocate the comment in v17 to
>>>> put_pages(), we can continue discussing it there if I'm missing yours point.
>>>>  
>>>
>>> I'm just saying it would be worth mentioning that we're intentionally
>>> leaking memory if shmem->pages_use_count > 1. Something like:
>>>
>>> 	/**
>>> 	 * shmem->pages_use_count should be 1 when ->sgt != NULL and
>>> 	 * zero otherwise. If some users still hold a pages reference
>>> 	 * that's a bug, and we intentionally leak the pages so they
>>> 	 * can't be re-allocated to someone else while the GPU/CPU
>>> 	 * still have access to it.
>>> 	 */
>>> 	drm_WARN_ON(drm,
>>> 		    refcount_read(&shmem->pages_use_count) == (shmem->sgt ? 1 : 0));
>>> 	if (shmem->sgt && refcount_dec_and_test(&shmem->pages_use_count))
>>> 		drm_gem_shmem_free_pages(shmem);  
>>
>> That may be acceptable, but only once there will a driver using this
>> feature.
> 
> Which feature? That's not related to a specific feature, that's just
> how drm_gem_shmem_get_pages_sgt() works, it takes a pages ref that can
> only be released in drm_gem_shmem_free(), because sgt users are not
> refcounted and the sgt stays around until the GEM object is freed or
> its pages are evicted. The only valid cases we have at the moment are:
> 
> - pages_use_count == 1 && sgt != NULL
> - pages_use_count == 0
> 
> any other situations are buggy.

sgt may belong to dma-buf for which pages_use_count=0, this can't be
done until sgt mess is sorted out

-- 
Best regards,
Dmitry

Re: [PATCH v16 15/20] drm/shmem-helper: Add memory shrinker

[Boris Brezillon]

On Thu, 14 Sep 2023 14:36:23 +0300
Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:

> On 9/14/23 11:27, Boris Brezillon wrote:
> > On Thu, 14 Sep 2023 10:50:32 +0300
> > Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
> >   
> >> On 9/14/23 10:36, Boris Brezillon wrote:  
> >>> On Thu, 14 Sep 2023 07:02:52 +0300
> >>> Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
> >>>     
> >>>> On 9/13/23 10:48, Boris Brezillon wrote:    
> >>>>> On Wed, 13 Sep 2023 03:56:14 +0300
> >>>>> Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
> >>>>>       
> >>>>>> On 9/5/23 11:03, Boris Brezillon wrote:      
> >>>>>>>>                * But
> >>>>>>>> +		 * acquiring the obj lock in drm_gem_shmem_release_pages_locked() can
> >>>>>>>> +		 * cause a locking order inversion between reservation_ww_class_mutex
> >>>>>>>> +		 * and fs_reclaim.
> >>>>>>>> +		 *
> >>>>>>>> +		 * This deadlock is not actually possible, because no one should
> >>>>>>>> +		 * be already holding the lock when drm_gem_shmem_free() is called.
> >>>>>>>> +		 * Unfortunately lockdep is not aware of this detail.  So when the
> >>>>>>>> +		 * refcount drops to zero, don't touch the reservation lock.
> >>>>>>>> +		 */
> >>>>>>>> +		if (shmem->got_pages_sgt &&
> >>>>>>>> +		    refcount_dec_and_test(&shmem->pages_use_count)) {
> >>>>>>>> +			drm_gem_shmem_do_release_pages_locked(shmem);
> >>>>>>>> +			shmem->got_pages_sgt = false;
> >>>>>>>>  		}        
> >>>>>>> Leaking memory is the right thing to do if pages_use_count > 1 (it's
> >>>>>>> better to leak than having someone access memory it no longer owns), but
> >>>>>>> I think it's worth mentioning in the above comment.        
> >>>>>>
> >>>>>> It's unlikely that it will be only a leak without a following up
> >>>>>> use-after-free. Neither is acceptable.      
> >>>>>
> >>>>> Not necessarily, if you have a page leak, it could be that the GPU has
> >>>>> access to those pages, but doesn't need the GEM object anymore
> >>>>> (pages are mapped by the iommu, which doesn't need shmem->sgt or
> >>>>> shmem->pages after the mapping is created). Without a WARN_ON(), this
> >>>>> can go unnoticed and lead to memory corruptions/information leaks.
> >>>>>       
> >>>>>>
> >>>>>> The drm_gem_shmem_free() could be changed such that kernel won't blow up
> >>>>>> on a refcnt bug, but that's not worthwhile doing because drivers
> >>>>>> shouldn't have silly bugs.      
> >>>>>
> >>>>> We definitely don't want to fix that, but we want to complain loudly
> >>>>> (WARN_ON()), and make sure the risk is limited (preventing memory from
> >>>>> being re-assigned to someone else by not freeing it).      
> >>>>
> >>>> That's what the code did and continues to do here. Not exactly sure what
> >>>> you're trying to say. I'm going to relocate the comment in v17 to
> >>>> put_pages(), we can continue discussing it there if I'm missing yours point.
> >>>>    
> >>>
> >>> I'm just saying it would be worth mentioning that we're intentionally
> >>> leaking memory if shmem->pages_use_count > 1. Something like:
> >>>
> >>> 	/**
> >>> 	 * shmem->pages_use_count should be 1 when ->sgt != NULL and
> >>> 	 * zero otherwise. If some users still hold a pages reference
> >>> 	 * that's a bug, and we intentionally leak the pages so they
> >>> 	 * can't be re-allocated to someone else while the GPU/CPU
> >>> 	 * still have access to it.
> >>> 	 */
> >>> 	drm_WARN_ON(drm,
> >>> 		    refcount_read(&shmem->pages_use_count) == (shmem->sgt ? 1 : 0));
> >>> 	if (shmem->sgt && refcount_dec_and_test(&shmem->pages_use_count))
> >>> 		drm_gem_shmem_free_pages(shmem);    
> >>
> >> That may be acceptable, but only once there will a driver using this
> >> feature.  
> > 
> > Which feature? That's not related to a specific feature, that's just
> > how drm_gem_shmem_get_pages_sgt() works, it takes a pages ref that can
> > only be released in drm_gem_shmem_free(), because sgt users are not
> > refcounted and the sgt stays around until the GEM object is freed or
> > its pages are evicted. The only valid cases we have at the moment are:
> > 
> > - pages_use_count == 1 && sgt != NULL
> > - pages_use_count == 0
> > 
> > any other situations are buggy.  
> 
> sgt may belong to dma-buf for which pages_use_count=0, this can't be
> done until sgt mess is sorted out

No it can't, not in that path, because the code you're adding is in the
if (!obj->import_branch) branch:


 	if (obj->import_attach) {
 		drm_prime_gem_destroy(obj, shmem->sgt);
 	} else {
		...
		// Your changes are here.
		...
	}
> 

Re: [PATCH v16 15/20] drm/shmem-helper: Add memory shrinker

[Dmitry Osipenko]

On 9/14/23 14:58, Boris Brezillon wrote:
> On Thu, 14 Sep 2023 14:36:23 +0300
> Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
> 
>> On 9/14/23 11:27, Boris Brezillon wrote:
>>> On Thu, 14 Sep 2023 10:50:32 +0300
>>> Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
>>>   
>>>> On 9/14/23 10:36, Boris Brezillon wrote:  
>>>>> On Thu, 14 Sep 2023 07:02:52 +0300
>>>>> Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
>>>>>     
>>>>>> On 9/13/23 10:48, Boris Brezillon wrote:    
>>>>>>> On Wed, 13 Sep 2023 03:56:14 +0300
>>>>>>> Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
>>>>>>>       
>>>>>>>> On 9/5/23 11:03, Boris Brezillon wrote:      
>>>>>>>>>>                * But
>>>>>>>>>> +		 * acquiring the obj lock in drm_gem_shmem_release_pages_locked() can
>>>>>>>>>> +		 * cause a locking order inversion between reservation_ww_class_mutex
>>>>>>>>>> +		 * and fs_reclaim.
>>>>>>>>>> +		 *
>>>>>>>>>> +		 * This deadlock is not actually possible, because no one should
>>>>>>>>>> +		 * be already holding the lock when drm_gem_shmem_free() is called.
>>>>>>>>>> +		 * Unfortunately lockdep is not aware of this detail.  So when the
>>>>>>>>>> +		 * refcount drops to zero, don't touch the reservation lock.
>>>>>>>>>> +		 */
>>>>>>>>>> +		if (shmem->got_pages_sgt &&
>>>>>>>>>> +		    refcount_dec_and_test(&shmem->pages_use_count)) {
>>>>>>>>>> +			drm_gem_shmem_do_release_pages_locked(shmem);
>>>>>>>>>> +			shmem->got_pages_sgt = false;
>>>>>>>>>>  		}        
>>>>>>>>> Leaking memory is the right thing to do if pages_use_count > 1 (it's
>>>>>>>>> better to leak than having someone access memory it no longer owns), but
>>>>>>>>> I think it's worth mentioning in the above comment.        
>>>>>>>>
>>>>>>>> It's unlikely that it will be only a leak without a following up
>>>>>>>> use-after-free. Neither is acceptable.      
>>>>>>>
>>>>>>> Not necessarily, if you have a page leak, it could be that the GPU has
>>>>>>> access to those pages, but doesn't need the GEM object anymore
>>>>>>> (pages are mapped by the iommu, which doesn't need shmem->sgt or
>>>>>>> shmem->pages after the mapping is created). Without a WARN_ON(), this
>>>>>>> can go unnoticed and lead to memory corruptions/information leaks.
>>>>>>>       
>>>>>>>>
>>>>>>>> The drm_gem_shmem_free() could be changed such that kernel won't blow up
>>>>>>>> on a refcnt bug, but that's not worthwhile doing because drivers
>>>>>>>> shouldn't have silly bugs.      
>>>>>>>
>>>>>>> We definitely don't want to fix that, but we want to complain loudly
>>>>>>> (WARN_ON()), and make sure the risk is limited (preventing memory from
>>>>>>> being re-assigned to someone else by not freeing it).      
>>>>>>
>>>>>> That's what the code did and continues to do here. Not exactly sure what
>>>>>> you're trying to say. I'm going to relocate the comment in v17 to
>>>>>> put_pages(), we can continue discussing it there if I'm missing yours point.
>>>>>>    
>>>>>
>>>>> I'm just saying it would be worth mentioning that we're intentionally
>>>>> leaking memory if shmem->pages_use_count > 1. Something like:
>>>>>
>>>>> 	/**
>>>>> 	 * shmem->pages_use_count should be 1 when ->sgt != NULL and
>>>>> 	 * zero otherwise. If some users still hold a pages reference
>>>>> 	 * that's a bug, and we intentionally leak the pages so they
>>>>> 	 * can't be re-allocated to someone else while the GPU/CPU
>>>>> 	 * still have access to it.
>>>>> 	 */
>>>>> 	drm_WARN_ON(drm,
>>>>> 		    refcount_read(&shmem->pages_use_count) == (shmem->sgt ? 1 : 0));
>>>>> 	if (shmem->sgt && refcount_dec_and_test(&shmem->pages_use_count))
>>>>> 		drm_gem_shmem_free_pages(shmem);    
>>>>
>>>> That may be acceptable, but only once there will a driver using this
>>>> feature.  
>>>
>>> Which feature? That's not related to a specific feature, that's just
>>> how drm_gem_shmem_get_pages_sgt() works, it takes a pages ref that can
>>> only be released in drm_gem_shmem_free(), because sgt users are not
>>> refcounted and the sgt stays around until the GEM object is freed or
>>> its pages are evicted. The only valid cases we have at the moment are:
>>>
>>> - pages_use_count == 1 && sgt != NULL
>>> - pages_use_count == 0
>>>
>>> any other situations are buggy.  
>>
>> sgt may belong to dma-buf for which pages_use_count=0, this can't be
>> done until sgt mess is sorted out
> 
> No it can't, not in that path, because the code you're adding is in the
> if (!obj->import_branch) branch:
> 
> 
>  	if (obj->import_attach) {
>  		drm_prime_gem_destroy(obj, shmem->sgt);
>  	} else {
> 		...
> 		// Your changes are here.
> 		...

This branch is taken for the dma-buf in the prime import error code path. But yes, the pages_use_count=0 for the dma-buf and then it can be written as:

	if (obj->import_attach) {
		drm_prime_gem_destroy(obj, shmem->sgt);
	} else {
		drm_WARN_ON(obj->dev, refcount_read(&shmem->vmap_use_count));

		if (shmem->sgt && refcount_read(&shmem->pages_use_count)) {
			dma_unmap_sgtable(obj->dev->dev, shmem->sgt,
					  DMA_BIDIRECTIONAL, 0);
			sg_free_table(shmem->sgt);
			kfree(shmem->sgt);

			__drm_gem_shmem_put_pages(shmem);
		}

		drm_WARN_ON(obj->dev, refcount_read(&shmem->pages_use_count));

Alright, I'll check if it works as expected for fixing the error code path bug for v17

-- 
Best regards,
Dmitry

Re: [PATCH v16 15/20] drm/shmem-helper: Add memory shrinker

[Boris Brezillon]

On Thu, 14 Sep 2023 16:01:37 +0300
Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:

> On 9/14/23 14:58, Boris Brezillon wrote:
> > On Thu, 14 Sep 2023 14:36:23 +0300
> > Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
> >   
> >> On 9/14/23 11:27, Boris Brezillon wrote:  
> >>> On Thu, 14 Sep 2023 10:50:32 +0300
> >>> Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
> >>>     
> >>>> On 9/14/23 10:36, Boris Brezillon wrote:    
> >>>>> On Thu, 14 Sep 2023 07:02:52 +0300
> >>>>> Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
> >>>>>       
> >>>>>> On 9/13/23 10:48, Boris Brezillon wrote:      
> >>>>>>> On Wed, 13 Sep 2023 03:56:14 +0300
> >>>>>>> Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
> >>>>>>>         
> >>>>>>>> On 9/5/23 11:03, Boris Brezillon wrote:        
> >>>>>>>>>>                * But
> >>>>>>>>>> +		 * acquiring the obj lock in drm_gem_shmem_release_pages_locked() can
> >>>>>>>>>> +		 * cause a locking order inversion between reservation_ww_class_mutex
> >>>>>>>>>> +		 * and fs_reclaim.
> >>>>>>>>>> +		 *
> >>>>>>>>>> +		 * This deadlock is not actually possible, because no one should
> >>>>>>>>>> +		 * be already holding the lock when drm_gem_shmem_free() is called.
> >>>>>>>>>> +		 * Unfortunately lockdep is not aware of this detail.  So when the
> >>>>>>>>>> +		 * refcount drops to zero, don't touch the reservation lock.
> >>>>>>>>>> +		 */
> >>>>>>>>>> +		if (shmem->got_pages_sgt &&
> >>>>>>>>>> +		    refcount_dec_and_test(&shmem->pages_use_count)) {
> >>>>>>>>>> +			drm_gem_shmem_do_release_pages_locked(shmem);
> >>>>>>>>>> +			shmem->got_pages_sgt = false;
> >>>>>>>>>>  		}          
> >>>>>>>>> Leaking memory is the right thing to do if pages_use_count > 1 (it's
> >>>>>>>>> better to leak than having someone access memory it no longer owns), but
> >>>>>>>>> I think it's worth mentioning in the above comment.          
> >>>>>>>>
> >>>>>>>> It's unlikely that it will be only a leak without a following up
> >>>>>>>> use-after-free. Neither is acceptable.        
> >>>>>>>
> >>>>>>> Not necessarily, if you have a page leak, it could be that the GPU has
> >>>>>>> access to those pages, but doesn't need the GEM object anymore
> >>>>>>> (pages are mapped by the iommu, which doesn't need shmem->sgt or
> >>>>>>> shmem->pages after the mapping is created). Without a WARN_ON(), this
> >>>>>>> can go unnoticed and lead to memory corruptions/information leaks.
> >>>>>>>         
> >>>>>>>>
> >>>>>>>> The drm_gem_shmem_free() could be changed such that kernel won't blow up
> >>>>>>>> on a refcnt bug, but that's not worthwhile doing because drivers
> >>>>>>>> shouldn't have silly bugs.        
> >>>>>>>
> >>>>>>> We definitely don't want to fix that, but we want to complain loudly
> >>>>>>> (WARN_ON()), and make sure the risk is limited (preventing memory from
> >>>>>>> being re-assigned to someone else by not freeing it).        
> >>>>>>
> >>>>>> That's what the code did and continues to do here. Not exactly sure what
> >>>>>> you're trying to say. I'm going to relocate the comment in v17 to
> >>>>>> put_pages(), we can continue discussing it there if I'm missing yours point.
> >>>>>>      
> >>>>>
> >>>>> I'm just saying it would be worth mentioning that we're intentionally
> >>>>> leaking memory if shmem->pages_use_count > 1. Something like:
> >>>>>
> >>>>> 	/**
> >>>>> 	 * shmem->pages_use_count should be 1 when ->sgt != NULL and
> >>>>> 	 * zero otherwise. If some users still hold a pages reference
> >>>>> 	 * that's a bug, and we intentionally leak the pages so they
> >>>>> 	 * can't be re-allocated to someone else while the GPU/CPU
> >>>>> 	 * still have access to it.
> >>>>> 	 */
> >>>>> 	drm_WARN_ON(drm,
> >>>>> 		    refcount_read(&shmem->pages_use_count) == (shmem->sgt ? 1 : 0));
> >>>>> 	if (shmem->sgt && refcount_dec_and_test(&shmem->pages_use_count))
> >>>>> 		drm_gem_shmem_free_pages(shmem);      
> >>>>
> >>>> That may be acceptable, but only once there will a driver using this
> >>>> feature.    
> >>>
> >>> Which feature? That's not related to a specific feature, that's just
> >>> how drm_gem_shmem_get_pages_sgt() works, it takes a pages ref that can
> >>> only be released in drm_gem_shmem_free(), because sgt users are not
> >>> refcounted and the sgt stays around until the GEM object is freed or
> >>> its pages are evicted. The only valid cases we have at the moment are:
> >>>
> >>> - pages_use_count == 1 && sgt != NULL
> >>> - pages_use_count == 0
> >>>
> >>> any other situations are buggy.    
> >>
> >> sgt may belong to dma-buf for which pages_use_count=0, this can't be
> >> done until sgt mess is sorted out  
> > 
> > No it can't, not in that path, because the code you're adding is in the
> > if (!obj->import_branch) branch:
> > 
> > 
> >  	if (obj->import_attach) {
> >  		drm_prime_gem_destroy(obj, shmem->sgt);
> >  	} else {
> > 		...
> > 		// Your changes are here.
> > 		...  
> 
> This branch is taken for the dma-buf in the prime import error code path.

I suggested a fix for this error that didn't involve adding a new flag,
but that's orthogonal to the piece of code we're discussing anyway.

> But yes, the pages_use_count=0 for the dma-buf and then it can be
> written as:
> 
> 	if (obj->import_attach) {
> 		drm_prime_gem_destroy(obj, shmem->sgt);
> 	} else {
> 		drm_WARN_ON(obj->dev, refcount_read(&shmem->vmap_use_count));
> 
> 		if (shmem->sgt && refcount_read(&shmem->pages_use_count)) {

You should drop the '&& refcount_read(&shmem->pages_use_count)',
otherwise you'll never enter this branch (sgt allocation retained
a ref, so pages_use_count > 0 when ->sgt != NULL).

If you added this pages_use_count > 0 check to deal with the
'free-partially-imported-GEM' case, I keep thinking this is not
the right fix. You should just assume that obj->import_attach == NULL
means not-a-prime-buffer, and then make sure
partially-initialized-prime-GEMs have import_attach assigned (see the
oneliner I suggested in my review of
`[PATCH v15 01/23] drm/shmem-helper: Fix UAF in error path when
freeing SGT of imported GEM`).

> 			dma_unmap_sgtable(obj->dev->dev, shmem->sgt,
> 					  DMA_BIDIRECTIONAL, 0);
> 			sg_free_table(shmem->sgt);
> 			kfree(shmem->sgt);
> 
> 			__drm_gem_shmem_put_pages(shmem);

You need to decrement pages_use_count:

			/* shmem->pages_use_count should be 1 when ->sgt != NULL and
			 * zero otherwise. If some users still hold a pages reference
			 * that's a bug, and we intentionally leak the pages so they
			 * can't be re-allocated to someone else while the GPU/CPU
			 * still have access to it.
		 	 */
			if (refcount_dec_and_test(&shmem->pages_use_count))
				__drm_gem_shmem_put_pages(shmem);

> 		}
> 
> 		drm_WARN_ON(obj->dev, refcount_read(&shmem->pages_use_count));

And now this WARN_ON() ^ should catch unexpected pages leak.

> 
> Alright, I'll check if it works as expected for fixing the error code path bug for v17
> 

Re: [PATCH v16 15/20] drm/shmem-helper: Add memory shrinker

[Boris Brezillon]

On Thu, 14 Sep 2023 15:27:03 +0200
Boris Brezillon <boris.brezillon@collabora.com> wrote:

> You should drop the '&& refcount_read(&shmem->pages_use_count)',
> otherwise you'll never enter this branch (sgt allocation retained
> a ref, so pages_use_count > 0 when ->sgt != NULL).

Sorry for the brain fart. You can drop this extra test because its
redundant (->sgt != NULL implies pages_use_count > 0), but it shouldn't
prevent you from entering the branch.

Re: [PATCH v16 15/20] drm/shmem-helper: Add memory shrinker

[Dmitry Osipenko]

On 9/14/23 16:27, Boris Brezillon wrote:
...
> If you added this pages_use_count > 0 check to deal with the
> 'free-partially-imported-GEM' case, I keep thinking this is not
> the right fix. You should just assume that obj->import_attach == NULL
> means not-a-prime-buffer, and then make sure
> partially-initialized-prime-GEMs have import_attach assigned (see the
> oneliner I suggested in my review of
> `[PATCH v15 01/23] drm/shmem-helper: Fix UAF in error path when
> freeing SGT of imported GEM`).

Yes, I added it to deal with the partially imported GEM. The
obj->import_attach can't be set until dma-buf is fully imported as it
also will cause trouble for the error code path, now dma-buf will be
freed two times.

>> 			dma_unmap_sgtable(obj->dev->dev, shmem->sgt,
>> 					  DMA_BIDIRECTIONAL, 0);
>> 			sg_free_table(shmem->sgt);
>> 			kfree(shmem->sgt);
>>
>> 			__drm_gem_shmem_put_pages(shmem);
> You need to decrement pages_use_count:
> 
> 			/* shmem->pages_use_count should be 1 when ->sgt != NULL and
> 			 * zero otherwise. If some users still hold a pages reference
> 			 * that's a bug, and we intentionally leak the pages so they
> 			 * can't be re-allocated to someone else while the GPU/CPU
> 			 * still have access to it.
> 		 	 */
> 			if (refcount_dec_and_test(&shmem->pages_use_count))
> 				__drm_gem_shmem_put_pages(shmem);
> 

The put_pages() itself decrements the refcnt.

I'm going back to deferring all this questionable changes for the later
times. It is not essential problem for this patchset.

-- 
Best regards,
Dmitry

Re: [PATCH v16 15/20] drm/shmem-helper: Add memory shrinker

[Dan Carpenter]

Hi Dmitry,

kernel test robot noticed the following build warnings:

https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Dmitry-Osipenko/drm-shmem-helper-Fix-UAF-in-error-path-when-freeing-SGT-of-imported-GEM/20230904-011037
base:   linus/master
patch link:    https://lore.kernel.org/r/20230903170736.513347-16-dmitry.osipenko%40collabora.com
patch subject: [PATCH v16 15/20] drm/shmem-helper: Add memory shrinker
config: x86_64-randconfig-161-20230907 (https://download.01.org/0day-ci/archive/20230907/202309070814.jyGJOJzY-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce: (https://download.01.org/0day-ci/archive/20230907/202309070814.jyGJOJzY-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
| Closes: https://lore.kernel.org/r/202309070814.jyGJOJzY-lkp@intel.com/

smatch warnings:
drivers/gpu/drm/drm_gem_shmem_helper.c:733 drm_gem_shmem_fault() error: we previously assumed 'shmem->pages' could be null (see line 724)

vim +733 drivers/gpu/drm/drm_gem_shmem_helper.c

2194a63a818db7 Noralf Trønnes  2019-03-12  702  static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
2194a63a818db7 Noralf Trønnes  2019-03-12  703  {
2194a63a818db7 Noralf Trønnes  2019-03-12  704  	struct vm_area_struct *vma = vmf->vma;
2194a63a818db7 Noralf Trønnes  2019-03-12  705  	struct drm_gem_object *obj = vma->vm_private_data;
2194a63a818db7 Noralf Trønnes  2019-03-12  706  	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
2194a63a818db7 Noralf Trønnes  2019-03-12  707  	loff_t num_pages = obj->size >> PAGE_SHIFT;
d611b4a0907cec Neil Roberts    2021-02-23  708  	vm_fault_t ret;
2194a63a818db7 Noralf Trønnes  2019-03-12  709  	struct page *page;
11d5a4745e00e7 Neil Roberts    2021-02-23  710  	pgoff_t page_offset;
2c607edf57db6a Dmitry Osipenko 2023-09-03  711  	bool pages_unpinned;
2c607edf57db6a Dmitry Osipenko 2023-09-03  712  	int err;
11d5a4745e00e7 Neil Roberts    2021-02-23  713  
11d5a4745e00e7 Neil Roberts    2021-02-23  714  	/* We don't use vmf->pgoff since that has the fake offset */
11d5a4745e00e7 Neil Roberts    2021-02-23  715  	page_offset = (vmf->address - vma->vm_start) >> PAGE_SHIFT;
2194a63a818db7 Noralf Trønnes  2019-03-12  716  
21aa27ddc58269 Dmitry Osipenko 2023-05-30  717  	dma_resv_lock(shmem->base.resv, NULL);
2194a63a818db7 Noralf Trønnes  2019-03-12  718  
2c607edf57db6a Dmitry Osipenko 2023-09-03  719  	/* Sanity-check that we have the pages pointer when it should present */
2c607edf57db6a Dmitry Osipenko 2023-09-03  720  	pages_unpinned = (shmem->evicted || shmem->madv < 0 ||
2c607edf57db6a Dmitry Osipenko 2023-09-03  721  			  !refcount_read(&shmem->pages_use_count));
2c607edf57db6a Dmitry Osipenko 2023-09-03  722  	drm_WARN_ON_ONCE(obj->dev, !shmem->pages ^ pages_unpinned);
2c607edf57db6a Dmitry Osipenko 2023-09-03  723  
2c607edf57db6a Dmitry Osipenko 2023-09-03 @724  	if (page_offset >= num_pages || (!shmem->pages && !shmem->evicted)) {
                                                                                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Should this be || instead of &&?  (The other thing that people do is
add "!shmem->evicted" for readability even though it doesn't need to be
checked.  So maybe that's the issue, but the checker assumes it needs to
be checked).

d611b4a0907cec Neil Roberts    2021-02-23  725  		ret = VM_FAULT_SIGBUS;
d611b4a0907cec Neil Roberts    2021-02-23  726  	} else {
2c607edf57db6a Dmitry Osipenko 2023-09-03  727  		err = drm_gem_shmem_swapin_locked(shmem);

Or maybe it's because the kbuild bot can't use the cross function db
and shmem->pages is assigned here?

2c607edf57db6a Dmitry Osipenko 2023-09-03  728  		if (err) {
2c607edf57db6a Dmitry Osipenko 2023-09-03  729  			ret = VM_FAULT_OOM;
2c607edf57db6a Dmitry Osipenko 2023-09-03  730  			goto unlock;
2c607edf57db6a Dmitry Osipenko 2023-09-03  731  		}
2c607edf57db6a Dmitry Osipenko 2023-09-03  732  
11d5a4745e00e7 Neil Roberts    2021-02-23 @733  		page = shmem->pages[page_offset];
                                                                       ^^^^^^^^^^^^
Unchecked dereference

2194a63a818db7 Noralf Trønnes  2019-03-12  734  
8b93d1d7dbd578 Daniel Vetter   2021-08-12  735  		ret = vmf_insert_pfn(vma, vmf->address, page_to_pfn(page));
d611b4a0907cec Neil Roberts    2021-02-23  736  	}
d611b4a0907cec Neil Roberts    2021-02-23  737  
2c607edf57db6a Dmitry Osipenko 2023-09-03  738  unlock:
21aa27ddc58269 Dmitry Osipenko 2023-05-30  739  	dma_resv_unlock(shmem->base.resv);
d611b4a0907cec Neil Roberts    2021-02-23  740  
d611b4a0907cec Neil Roberts    2021-02-23  741  	return ret;
2194a63a818db7 Noralf Trønnes  2019-03-12  742  }

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v16 15/20] drm/shmem-helper: Add memory shrinker

[Dmitry Osipenko]

On 9/7/23 13:03, Dan Carpenter wrote:
> 2c607edf57db6a Dmitry Osipenko 2023-09-03 @724  	if (page_offset >= num_pages || (!shmem->pages && !shmem->evicted)) {
>                                                                                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> Should this be || instead of &&?  (The other thing that people do is
> add "!shmem->evicted" for readability even though it doesn't need to be
> checked.  So maybe that's the issue, but the checker assumes it needs to
> be checked).
> 
> d611b4a0907cec Neil Roberts    2021-02-23  725  		ret = VM_FAULT_SIGBUS;
> d611b4a0907cec Neil Roberts    2021-02-23  726  	} else {
> 2c607edf57db6a Dmitry Osipenko 2023-09-03  727  		err = drm_gem_shmem_swapin_locked(shmem);
> 
> Or maybe it's because the kbuild bot can't use the cross function db
> and shmem->pages is assigned here?

Should be a function db problem. The shmem->pages won't be NULL if
drm_gem_shmem_swapin_locked() succeeds.

-- 
Best regards,
Dmitry

[PATCH v16 16/20] drm/shmem-helper: Export drm_gem_shmem_get_pages_sgt_locked()

[Dmitry Osipenko]

Export drm_gem_shmem_get_pages_sgt_locked() that will be used by virtio-gpu
shrinker during GEM swap-in operation done under the held reservation lock.

Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 3 ++-
 include/drm/drm_gem_shmem_helper.h     | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index a0a6c7e505c8..afd9b97ba593 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -874,7 +874,7 @@ struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_shmem_object *shmem)
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_get_sg_table);
 
-static struct sg_table *drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_object *shmem)
+struct sg_table *drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_object *shmem)
 {
 	struct drm_gem_object *obj = &shmem->base;
 	int ret;
@@ -919,6 +919,7 @@ static struct sg_table *drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_
 	drm_gem_shmem_put_pages_locked(shmem);
 	return ERR_PTR(ret);
 }
+EXPORT_SYMBOL_GPL(drm_gem_shmem_get_pages_sgt_locked);
 
 /**
  * drm_gem_shmem_get_pages_sgt - Pin pages, dma map them, and return a
diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
index 65c99da25048..2d7debc23ac1 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -161,6 +161,7 @@ void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem);
 
 struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_shmem_object *shmem);
 struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_shmem_object *shmem);
+struct sg_table *drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_object *shmem);
 
 void drm_gem_shmem_print_info(const struct drm_gem_shmem_object *shmem,
 			      struct drm_printer *p, unsigned int indent);
-- 
2.41.0

[PATCH v16 17/20] drm/virtio: Pin display framebuffer BO

[Dmitry Osipenko]

Prepare to addition of memory shrinker support by pinning display
framebuffer BO pages in memory while they are in use by display on host.
Shrinker is free to relocate framebuffer BO pages if it doesn't know that
pages are in use, thus pin the pages to disallow shrinker to move them.

Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/virtio/virtgpu_drv.h   |  2 ++
 drivers/gpu/drm/virtio/virtgpu_gem.c   | 19 +++++++++++++++++++
 drivers/gpu/drm/virtio/virtgpu_plane.c | 17 +++++++++++++++--
 3 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h
index 4126c384286b..5a4b74b7b318 100644
--- a/drivers/gpu/drm/virtio/virtgpu_drv.h
+++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
@@ -313,6 +313,8 @@ void virtio_gpu_array_put_free(struct virtio_gpu_object_array *objs);
 void virtio_gpu_array_put_free_delayed(struct virtio_gpu_device *vgdev,
 				       struct virtio_gpu_object_array *objs);
 void virtio_gpu_array_put_free_work(struct work_struct *work);
+int virtio_gpu_gem_pin(struct virtio_gpu_object *bo);
+void virtio_gpu_gem_unpin(struct virtio_gpu_object *bo);
 
 /* virtgpu_vq.c */
 int virtio_gpu_alloc_vbufs(struct virtio_gpu_device *vgdev);
diff --git a/drivers/gpu/drm/virtio/virtgpu_gem.c b/drivers/gpu/drm/virtio/virtgpu_gem.c
index 7db48d17ee3a..625c05d625bf 100644
--- a/drivers/gpu/drm/virtio/virtgpu_gem.c
+++ b/drivers/gpu/drm/virtio/virtgpu_gem.c
@@ -294,3 +294,22 @@ void virtio_gpu_array_put_free_work(struct work_struct *work)
 	}
 	spin_unlock(&vgdev->obj_free_lock);
 }
+
+int virtio_gpu_gem_pin(struct virtio_gpu_object *bo)
+{
+	int err;
+
+	if (virtio_gpu_is_shmem(bo)) {
+		err = drm_gem_shmem_pin(&bo->base);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+void virtio_gpu_gem_unpin(struct virtio_gpu_object *bo)
+{
+	if (virtio_gpu_is_shmem(bo))
+		drm_gem_shmem_unpin(&bo->base);
+}
diff --git a/drivers/gpu/drm/virtio/virtgpu_plane.c b/drivers/gpu/drm/virtio/virtgpu_plane.c
index a2e045f3a000..def57b01a826 100644
--- a/drivers/gpu/drm/virtio/virtgpu_plane.c
+++ b/drivers/gpu/drm/virtio/virtgpu_plane.c
@@ -238,20 +238,28 @@ static int virtio_gpu_plane_prepare_fb(struct drm_plane *plane,
 	struct virtio_gpu_device *vgdev = dev->dev_private;
 	struct virtio_gpu_framebuffer *vgfb;
 	struct virtio_gpu_object *bo;
+	int err;
 
 	if (!new_state->fb)
 		return 0;
 
 	vgfb = to_virtio_gpu_framebuffer(new_state->fb);
 	bo = gem_to_virtio_gpu_obj(vgfb->base.obj[0]);
-	if (!bo || (plane->type == DRM_PLANE_TYPE_PRIMARY && !bo->guest_blob))
+
+	err = virtio_gpu_gem_pin(bo);
+	if (err)
+		return err;
+
+	if (plane->type == DRM_PLANE_TYPE_PRIMARY && !bo->guest_blob)
 		return 0;
 
 	if (bo->dumb && (plane->state->fb != new_state->fb)) {
 		vgfb->fence = virtio_gpu_fence_alloc(vgdev, vgdev->fence_drv.context,
 						     0);
-		if (!vgfb->fence)
+		if (!vgfb->fence) {
+			virtio_gpu_gem_unpin(bo);
 			return -ENOMEM;
+		}
 	}
 
 	return 0;
@@ -261,15 +269,20 @@ static void virtio_gpu_plane_cleanup_fb(struct drm_plane *plane,
 					struct drm_plane_state *state)
 {
 	struct virtio_gpu_framebuffer *vgfb;
+	struct virtio_gpu_object *bo;
 
 	if (!state->fb)
 		return;
 
 	vgfb = to_virtio_gpu_framebuffer(state->fb);
+	bo = gem_to_virtio_gpu_obj(vgfb->base.obj[0]);
+
 	if (vgfb->fence) {
 		dma_fence_put(&vgfb->fence->f);
 		vgfb->fence = NULL;
 	}
+
+	virtio_gpu_gem_unpin(bo);
 }
 
 static void virtio_gpu_cursor_plane_update(struct drm_plane *plane,
-- 
2.41.0

[PATCH v16 18/20] drm/virtio: Attach shmem BOs dynamically

[Dmitry Osipenko]

Prepare for addition of memory shrinker support by attaching shmem pages
to host dynamically on first use. The attachment vq command wasn't fenced
and there was no vq kick made in the BO creation code path, hence the
the attachment already was happening dynamically, but implicitly. Making
attachment explicitly dynamic will allow to simplify and reuse more code
when shrinker will be added. The virtio_gpu_object_shmem_init() now works
under held reservation lock, which will be important to have for shrinker.

Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/virtio/virtgpu_drv.h    |  7 +++
 drivers/gpu/drm/virtio/virtgpu_gem.c    | 26 ++++++++
 drivers/gpu/drm/virtio/virtgpu_ioctl.c  | 32 ++++++----
 drivers/gpu/drm/virtio/virtgpu_object.c | 80 ++++++++++++++++++++-----
 drivers/gpu/drm/virtio/virtgpu_submit.c | 15 ++++-
 5 files changed, 132 insertions(+), 28 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h
index 5a4b74b7b318..8c82530eae82 100644
--- a/drivers/gpu/drm/virtio/virtgpu_drv.h
+++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
@@ -89,6 +89,7 @@ struct virtio_gpu_object {
 	uint32_t hw_res_handle;
 	bool dumb;
 	bool created;
+	bool detached;
 	bool host3d_blob, guest_blob;
 	uint32_t blob_mem, blob_flags;
 
@@ -313,6 +314,8 @@ void virtio_gpu_array_put_free(struct virtio_gpu_object_array *objs);
 void virtio_gpu_array_put_free_delayed(struct virtio_gpu_device *vgdev,
 				       struct virtio_gpu_object_array *objs);
 void virtio_gpu_array_put_free_work(struct work_struct *work);
+int virtio_gpu_array_prepare(struct virtio_gpu_device *vgdev,
+			     struct virtio_gpu_object_array *objs);
 int virtio_gpu_gem_pin(struct virtio_gpu_object *bo);
 void virtio_gpu_gem_unpin(struct virtio_gpu_object *bo);
 
@@ -458,6 +461,10 @@ int virtio_gpu_object_create(struct virtio_gpu_device *vgdev,
 
 bool virtio_gpu_is_shmem(struct virtio_gpu_object *bo);
 
+int virtio_gpu_reattach_shmem_object_locked(struct virtio_gpu_object *bo);
+
+int virtio_gpu_reattach_shmem_object(struct virtio_gpu_object *bo);
+
 int virtio_gpu_resource_id_get(struct virtio_gpu_device *vgdev,
 			       uint32_t *resid);
 /* virtgpu_prime.c */
diff --git a/drivers/gpu/drm/virtio/virtgpu_gem.c b/drivers/gpu/drm/virtio/virtgpu_gem.c
index 625c05d625bf..97e67064c97e 100644
--- a/drivers/gpu/drm/virtio/virtgpu_gem.c
+++ b/drivers/gpu/drm/virtio/virtgpu_gem.c
@@ -295,6 +295,26 @@ void virtio_gpu_array_put_free_work(struct work_struct *work)
 	spin_unlock(&vgdev->obj_free_lock);
 }
 
+int virtio_gpu_array_prepare(struct virtio_gpu_device *vgdev,
+			     struct virtio_gpu_object_array *objs)
+{
+	struct virtio_gpu_object *bo;
+	int ret = 0;
+	u32 i;
+
+	for (i = 0; i < objs->nents; i++) {
+		bo = gem_to_virtio_gpu_obj(objs->objs[i]);
+
+		if (virtio_gpu_is_shmem(bo) && bo->detached) {
+			ret = virtio_gpu_reattach_shmem_object_locked(bo);
+			if (ret)
+				break;
+		}
+	}
+
+	return ret;
+}
+
 int virtio_gpu_gem_pin(struct virtio_gpu_object *bo)
 {
 	int err;
@@ -303,6 +323,12 @@ int virtio_gpu_gem_pin(struct virtio_gpu_object *bo)
 		err = drm_gem_shmem_pin(&bo->base);
 		if (err)
 			return err;
+
+		err = virtio_gpu_reattach_shmem_object(bo);
+		if (err) {
+			drm_gem_shmem_unpin(&bo->base);
+			return err;
+		}
 	}
 
 	return 0;
diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
index b24b11f25197..070c29cea26a 100644
--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -246,6 +246,10 @@ static int virtio_gpu_transfer_from_host_ioctl(struct drm_device *dev,
 	if (ret != 0)
 		goto err_put_free;
 
+	ret = virtio_gpu_array_prepare(vgdev, objs);
+	if (ret)
+		goto err_unlock;
+
 	fence = virtio_gpu_fence_alloc(vgdev, vgdev->fence_drv.context, 0);
 	if (!fence) {
 		ret = -ENOMEM;
@@ -288,11 +292,25 @@ static int virtio_gpu_transfer_to_host_ioctl(struct drm_device *dev, void *data,
 		goto err_put_free;
 	}
 
+	ret = virtio_gpu_array_lock_resv(objs);
+	if (ret != 0)
+		goto err_put_free;
+
+	ret = virtio_gpu_array_prepare(vgdev, objs);
+	if (ret)
+		goto err_unlock;
+
+	fence = virtio_gpu_fence_alloc(vgdev, vgdev->fence_drv.context, 0);
+	if (!fence) {
+		ret = -ENOMEM;
+		goto err_unlock;
+	}
+
 	if (!vgdev->has_virgl_3d) {
 		virtio_gpu_cmd_transfer_to_host_2d
 			(vgdev, offset,
 			 args->box.w, args->box.h, args->box.x, args->box.y,
-			 objs, NULL);
+			 objs, fence);
 	} else {
 		virtio_gpu_create_context(dev, file);
 
@@ -301,23 +319,13 @@ static int virtio_gpu_transfer_to_host_ioctl(struct drm_device *dev, void *data,
 			goto err_put_free;
 		}
 
-		ret = virtio_gpu_array_lock_resv(objs);
-		if (ret != 0)
-			goto err_put_free;
-
-		ret = -ENOMEM;
-		fence = virtio_gpu_fence_alloc(vgdev, vgdev->fence_drv.context,
-					       0);
-		if (!fence)
-			goto err_unlock;
-
 		virtio_gpu_cmd_transfer_to_host_3d
 			(vgdev,
 			 vfpriv ? vfpriv->ctx_id : 0, offset, args->level,
 			 args->stride, args->layer_stride, &args->box, objs,
 			 fence);
-		dma_fence_put(&fence->f);
 	}
+	dma_fence_put(&fence->f);
 	virtio_gpu_notify(vgdev);
 	return 0;
 
diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c
index 97020ed56b81..044b08aa78ac 100644
--- a/drivers/gpu/drm/virtio/virtgpu_object.c
+++ b/drivers/gpu/drm/virtio/virtgpu_object.c
@@ -142,10 +142,13 @@ static int virtio_gpu_object_shmem_init(struct virtio_gpu_device *vgdev,
 	struct sg_table *pages;
 	int si;
 
-	pages = drm_gem_shmem_get_pages_sgt(&bo->base);
+	pages = drm_gem_shmem_get_pages_sgt_locked(&bo->base);
 	if (IS_ERR(pages))
 		return PTR_ERR(pages);
 
+	if (!ents)
+		return 0;
+
 	if (use_dma_api)
 		*nents = pages->nents;
 	else
@@ -176,6 +179,40 @@ static int virtio_gpu_object_shmem_init(struct virtio_gpu_device *vgdev,
 	return 0;
 }
 
+int virtio_gpu_reattach_shmem_object_locked(struct virtio_gpu_object *bo)
+{
+	struct virtio_gpu_device *vgdev = bo->base.base.dev->dev_private;
+	struct virtio_gpu_mem_entry *ents;
+	unsigned int nents;
+	int err;
+
+	if (!bo->detached)
+		return 0;
+
+	err = virtio_gpu_object_shmem_init(vgdev, bo, &ents, &nents);
+	if (err)
+		return err;
+
+	virtio_gpu_object_attach(vgdev, bo, ents, nents);
+
+	bo->detached = false;
+
+	return 0;
+}
+
+int virtio_gpu_reattach_shmem_object(struct virtio_gpu_object *bo)
+{
+	int ret;
+
+	ret = dma_resv_lock_interruptible(bo->base.base.resv, NULL);
+	if (ret)
+		return ret;
+	ret = virtio_gpu_reattach_shmem_object_locked(bo);
+	dma_resv_unlock(bo->base.base.resv);
+
+	return ret;
+}
+
 int virtio_gpu_object_create(struct virtio_gpu_device *vgdev,
 			     struct virtio_gpu_object_params *params,
 			     struct virtio_gpu_object **bo_ptr,
@@ -202,45 +239,60 @@ int virtio_gpu_object_create(struct virtio_gpu_device *vgdev,
 
 	bo->dumb = params->dumb;
 
-	ret = virtio_gpu_object_shmem_init(vgdev, bo, &ents, &nents);
-	if (ret != 0)
-		goto err_put_id;
+	if (bo->blob_mem == VIRTGPU_BLOB_MEM_GUEST)
+		bo->guest_blob = true;
 
 	if (fence) {
 		ret = -ENOMEM;
 		objs = virtio_gpu_array_alloc(1);
 		if (!objs)
-			goto err_free_entry;
+			goto err_put_id;
 		virtio_gpu_array_add_obj(objs, &bo->base.base);
 
 		ret = virtio_gpu_array_lock_resv(objs);
 		if (ret != 0)
 			goto err_put_objs;
+	} else {
+		ret = dma_resv_lock(bo->base.base.resv, NULL);
+		if (ret)
+			goto err_put_id;
 	}
 
 	if (params->blob) {
-		if (params->blob_mem == VIRTGPU_BLOB_MEM_GUEST)
-			bo->guest_blob = true;
+		ret = virtio_gpu_object_shmem_init(vgdev, bo, &ents, &nents);
+		if (ret)
+			goto err_unlock_objs;
+	} else {
+		ret = virtio_gpu_object_shmem_init(vgdev, bo, NULL, NULL);
+		if (ret)
+			goto err_unlock_objs;
 
+		bo->detached = true;
+	}
+
+	if (params->blob)
 		virtio_gpu_cmd_resource_create_blob(vgdev, bo, params,
 						    ents, nents);
-	} else if (params->virgl) {
+	else if (params->virgl)
 		virtio_gpu_cmd_resource_create_3d(vgdev, bo, params,
 						  objs, fence);
-		virtio_gpu_object_attach(vgdev, bo, ents, nents);
-	} else {
+	else
 		virtio_gpu_cmd_create_resource(vgdev, bo, params,
 					       objs, fence);
-		virtio_gpu_object_attach(vgdev, bo, ents, nents);
-	}
+
+	if (!fence)
+		dma_resv_unlock(bo->base.base.resv);
 
 	*bo_ptr = bo;
 	return 0;
 
+err_unlock_objs:
+	if (fence)
+		virtio_gpu_array_unlock_resv(objs);
+	else
+		dma_resv_unlock(bo->base.base.resv);
 err_put_objs:
 	virtio_gpu_array_put_free(objs);
-err_free_entry:
-	kvfree(ents);
 err_put_id:
 	virtio_gpu_resource_id_put(vgdev, bo->hw_res_handle);
 err_free_gem:
diff --git a/drivers/gpu/drm/virtio/virtgpu_submit.c b/drivers/gpu/drm/virtio/virtgpu_submit.c
index 3c00135ead45..94867f485a64 100644
--- a/drivers/gpu/drm/virtio/virtgpu_submit.c
+++ b/drivers/gpu/drm/virtio/virtgpu_submit.c
@@ -465,8 +465,19 @@ static void virtio_gpu_install_out_fence_fd(struct virtio_gpu_submit *submit)
 
 static int virtio_gpu_lock_buflist(struct virtio_gpu_submit *submit)
 {
-	if (submit->buflist)
-		return virtio_gpu_array_lock_resv(submit->buflist);
+	int err;
+
+	if (submit->buflist) {
+		err = virtio_gpu_array_lock_resv(submit->buflist);
+		if (err)
+			return err;
+
+		err = virtio_gpu_array_prepare(submit->vgdev, submit->buflist);
+		if (err) {
+			virtio_gpu_array_unlock_resv(submit->buflist);
+			return err;
+		}
+	}
 
 	return 0;
 }
-- 
2.41.0

[PATCH v16 19/20] drm/virtio: Support memory shrinking

[Dmitry Osipenko]

Support generic drm-shmem memory shrinker and add new madvise IOCTL to
the VirtIO-GPU driver. BO cache manager of Mesa driver will mark BOs as
"don't need" using the new IOCTL to let shrinker purge the marked BOs on
OOM, the shrinker will also evict unpurgeable shmem BOs from memory if
guest supports SWAP file or partition.

Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/virtio/virtgpu_drv.h    | 13 +++++-
 drivers/gpu/drm/virtio/virtgpu_gem.c    | 35 ++++++++++++++
 drivers/gpu/drm/virtio/virtgpu_ioctl.c  | 25 ++++++++++
 drivers/gpu/drm/virtio/virtgpu_kms.c    |  8 ++++
 drivers/gpu/drm/virtio/virtgpu_object.c | 61 +++++++++++++++++++++++++
 drivers/gpu/drm/virtio/virtgpu_vq.c     | 40 ++++++++++++++++
 include/uapi/drm/virtgpu_drm.h          | 14 ++++++
 7 files changed, 195 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h
index 8c82530eae82..a34da2036221 100644
--- a/drivers/gpu/drm/virtio/virtgpu_drv.h
+++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
@@ -278,7 +278,7 @@ struct virtio_gpu_fpriv {
 };
 
 /* virtgpu_ioctl.c */
-#define DRM_VIRTIO_NUM_IOCTLS 12
+#define DRM_VIRTIO_NUM_IOCTLS 13
 extern struct drm_ioctl_desc virtio_gpu_ioctls[DRM_VIRTIO_NUM_IOCTLS];
 void virtio_gpu_create_context(struct drm_device *dev, struct drm_file *file);
 
@@ -316,6 +316,8 @@ void virtio_gpu_array_put_free_delayed(struct virtio_gpu_device *vgdev,
 void virtio_gpu_array_put_free_work(struct work_struct *work);
 int virtio_gpu_array_prepare(struct virtio_gpu_device *vgdev,
 			     struct virtio_gpu_object_array *objs);
+int virtio_gpu_gem_host_mem_release(struct virtio_gpu_object *bo);
+int virtio_gpu_gem_madvise(struct virtio_gpu_object *obj, int madv);
 int virtio_gpu_gem_pin(struct virtio_gpu_object *bo);
 void virtio_gpu_gem_unpin(struct virtio_gpu_object *bo);
 
@@ -329,6 +331,8 @@ void virtio_gpu_cmd_create_resource(struct virtio_gpu_device *vgdev,
 				    struct virtio_gpu_fence *fence);
 void virtio_gpu_cmd_unref_resource(struct virtio_gpu_device *vgdev,
 				   struct virtio_gpu_object *bo);
+int virtio_gpu_cmd_release_resource(struct virtio_gpu_device *vgdev,
+				    struct virtio_gpu_object *bo);
 void virtio_gpu_cmd_transfer_to_host_2d(struct virtio_gpu_device *vgdev,
 					uint64_t offset,
 					uint32_t width, uint32_t height,
@@ -349,6 +353,9 @@ void virtio_gpu_object_attach(struct virtio_gpu_device *vgdev,
 			      struct virtio_gpu_object *obj,
 			      struct virtio_gpu_mem_entry *ents,
 			      unsigned int nents);
+void virtio_gpu_object_detach(struct virtio_gpu_device *vgdev,
+			      struct virtio_gpu_object *obj,
+			      struct virtio_gpu_fence *fence);
 int virtio_gpu_attach_status_page(struct virtio_gpu_device *vgdev);
 int virtio_gpu_detach_status_page(struct virtio_gpu_device *vgdev);
 void virtio_gpu_cursor_ping(struct virtio_gpu_device *vgdev,
@@ -499,4 +506,8 @@ void virtio_gpu_vram_unmap_dma_buf(struct device *dev,
 int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
 				struct drm_file *file);
 
+/* virtgpu_gem_shrinker.c */
+int virtio_gpu_gem_shrinker_init(struct virtio_gpu_device *vgdev);
+void virtio_gpu_gem_shrinker_fini(struct virtio_gpu_device *vgdev);
+
 #endif
diff --git a/drivers/gpu/drm/virtio/virtgpu_gem.c b/drivers/gpu/drm/virtio/virtgpu_gem.c
index 97e67064c97e..748f7bbb0e6d 100644
--- a/drivers/gpu/drm/virtio/virtgpu_gem.c
+++ b/drivers/gpu/drm/virtio/virtgpu_gem.c
@@ -147,10 +147,20 @@ void virtio_gpu_gem_object_close(struct drm_gem_object *obj,
 	struct virtio_gpu_device *vgdev = obj->dev->dev_private;
 	struct virtio_gpu_fpriv *vfpriv = file->driver_priv;
 	struct virtio_gpu_object_array *objs;
+	struct virtio_gpu_object *bo;
 
 	if (!vgdev->has_virgl_3d)
 		return;
 
+	bo = gem_to_virtio_gpu_obj(obj);
+
+	/*
+	 * Purged BO was already detached and released, the resource ID
+	 * is invalid by now.
+	 */
+	if (!virtio_gpu_gem_madvise(bo, VIRTGPU_MADV_WILLNEED))
+		return;
+
 	objs = virtio_gpu_array_alloc(1);
 	if (!objs)
 		return;
@@ -315,6 +325,31 @@ int virtio_gpu_array_prepare(struct virtio_gpu_device *vgdev,
 	return ret;
 }
 
+int virtio_gpu_gem_madvise(struct virtio_gpu_object *bo, int madv)
+{
+	if (virtio_gpu_is_shmem(bo))
+		return drm_gem_shmem_object_madvise(&bo->base.base, madv);
+
+	return 1;
+}
+
+int virtio_gpu_gem_host_mem_release(struct virtio_gpu_object *bo)
+{
+	struct virtio_gpu_device *vgdev = bo->base.base.dev->dev_private;
+	int err;
+
+	if (bo->created) {
+		err = virtio_gpu_cmd_release_resource(vgdev, bo);
+		if (err)
+			return err;
+
+		virtio_gpu_notify(vgdev);
+		bo->created = false;
+	}
+
+	return 0;
+}
+
 int virtio_gpu_gem_pin(struct virtio_gpu_object *bo)
 {
 	int err;
diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
index 070c29cea26a..44a99166efdc 100644
--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -676,6 +676,28 @@ static int virtio_gpu_context_init_ioctl(struct drm_device *dev,
 	return ret;
 }
 
+static int virtio_gpu_madvise_ioctl(struct drm_device *dev,
+				    void *data,
+				    struct drm_file *file)
+{
+	struct drm_virtgpu_madvise *args = data;
+	struct virtio_gpu_object *bo;
+	struct drm_gem_object *obj;
+
+	if (args->madv > VIRTGPU_MADV_DONTNEED)
+		return -EOPNOTSUPP;
+
+	obj = drm_gem_object_lookup(file, args->bo_handle);
+	if (!obj)
+		return -ENOENT;
+
+	bo = gem_to_virtio_gpu_obj(obj);
+	args->retained = virtio_gpu_gem_madvise(bo, args->madv);
+	drm_gem_object_put(obj);
+
+	return 0;
+}
+
 struct drm_ioctl_desc virtio_gpu_ioctls[DRM_VIRTIO_NUM_IOCTLS] = {
 	DRM_IOCTL_DEF_DRV(VIRTGPU_MAP, virtio_gpu_map_ioctl,
 			  DRM_RENDER_ALLOW),
@@ -715,4 +737,7 @@ struct drm_ioctl_desc virtio_gpu_ioctls[DRM_VIRTIO_NUM_IOCTLS] = {
 
 	DRM_IOCTL_DEF_DRV(VIRTGPU_CONTEXT_INIT, virtio_gpu_context_init_ioctl,
 			  DRM_RENDER_ALLOW),
+
+	DRM_IOCTL_DEF_DRV(VIRTGPU_MADVISE, virtio_gpu_madvise_ioctl,
+			  DRM_RENDER_ALLOW),
 };
diff --git a/drivers/gpu/drm/virtio/virtgpu_kms.c b/drivers/gpu/drm/virtio/virtgpu_kms.c
index 5a3b5aaed1f3..43e237082cec 100644
--- a/drivers/gpu/drm/virtio/virtgpu_kms.c
+++ b/drivers/gpu/drm/virtio/virtgpu_kms.c
@@ -245,6 +245,12 @@ int virtio_gpu_init(struct virtio_device *vdev, struct drm_device *dev)
 		goto err_scanouts;
 	}
 
+	ret = drmm_gem_shmem_init(dev);
+	if (ret) {
+		DRM_ERROR("shmem init failed\n");
+		goto err_modeset;
+	}
+
 	virtio_device_ready(vgdev->vdev);
 
 	if (num_capsets)
@@ -259,6 +265,8 @@ int virtio_gpu_init(struct virtio_device *vdev, struct drm_device *dev)
 	}
 	return 0;
 
+err_modeset:
+	virtio_gpu_modeset_fini(vgdev);
 err_scanouts:
 	virtio_gpu_free_vbufs(vgdev);
 err_vbufs:
diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c
index 044b08aa78ac..dc4df8f2d89c 100644
--- a/drivers/gpu/drm/virtio/virtgpu_object.c
+++ b/drivers/gpu/drm/virtio/virtgpu_object.c
@@ -97,6 +97,60 @@ static void virtio_gpu_free_object(struct drm_gem_object *obj)
 	virtio_gpu_cleanup_object(bo);
 }
 
+static int virtio_gpu_detach_object_fenced(struct virtio_gpu_object *bo)
+{
+	struct virtio_gpu_device *vgdev = bo->base.base.dev->dev_private;
+	struct virtio_gpu_fence *fence;
+
+	if (bo->detached)
+		return 0;
+
+	fence = virtio_gpu_fence_alloc(vgdev, vgdev->fence_drv.context, 0);
+	if (!fence)
+		return -ENOMEM;
+
+	virtio_gpu_object_detach(vgdev, bo, fence);
+	virtio_gpu_notify(vgdev);
+
+	dma_fence_wait(&fence->f, false);
+	dma_fence_put(&fence->f);
+
+	bo->detached = true;
+
+	return 0;
+}
+
+static int virtio_gpu_shmem_evict(struct drm_gem_object *obj)
+{
+	struct virtio_gpu_object *bo = gem_to_virtio_gpu_obj(obj);
+	int err;
+
+	/* blob is not movable, it's impossible to detach it from host */
+	if (bo->blob_mem)
+		return -EBUSY;
+
+	/*
+	 * At first tell host to stop using guest's memory to ensure that
+	 * host won't touch the released guest's memory once it's gone.
+	 */
+	err = virtio_gpu_detach_object_fenced(bo);
+	if (err)
+		return err;
+
+	if (drm_gem_shmem_is_purgeable(&bo->base)) {
+		err = virtio_gpu_gem_host_mem_release(bo);
+		if (err)
+			return err;
+
+		drm_gem_shmem_purge_locked(&bo->base);
+	} else {
+		bo->base.pages_mark_dirty_on_put = 1;
+		drm_gem_shmem_evict_locked(&bo->base);
+	}
+
+	return 0;
+}
+
 static const struct drm_gem_object_funcs virtio_gpu_shmem_funcs = {
 	.free = virtio_gpu_free_object,
 	.open = virtio_gpu_gem_object_open,
@@ -110,6 +164,7 @@ static const struct drm_gem_object_funcs virtio_gpu_shmem_funcs = {
 	.vunmap = drm_gem_shmem_object_vunmap_locked,
 	.mmap = drm_gem_shmem_object_mmap,
 	.vm_ops = &drm_gem_shmem_vm_ops,
+	.evict = virtio_gpu_shmem_evict,
 };
 
 bool virtio_gpu_is_shmem(struct virtio_gpu_object *bo)
@@ -189,6 +244,10 @@ int virtio_gpu_reattach_shmem_object_locked(struct virtio_gpu_object *bo)
 	if (!bo->detached)
 		return 0;
 
+	err = drm_gem_shmem_swapin_locked(&bo->base);
+	if (err)
+		return err;
+
 	err = virtio_gpu_object_shmem_init(vgdev, bo, &ents, &nents);
 	if (err)
 		return err;
@@ -238,6 +297,8 @@ int virtio_gpu_object_create(struct virtio_gpu_device *vgdev,
 		goto err_free_gem;
 
 	bo->dumb = params->dumb;
+	bo->blob_mem = params->blob_mem;
+	bo->blob_flags = params->blob_flags;
 
 	if (bo->blob_mem == VIRTGPU_BLOB_MEM_GUEST)
 		bo->guest_blob = true;
diff --git a/drivers/gpu/drm/virtio/virtgpu_vq.c b/drivers/gpu/drm/virtio/virtgpu_vq.c
index b1a00c0c25a7..14ab470f413a 100644
--- a/drivers/gpu/drm/virtio/virtgpu_vq.c
+++ b/drivers/gpu/drm/virtio/virtgpu_vq.c
@@ -545,6 +545,21 @@ void virtio_gpu_cmd_unref_resource(struct virtio_gpu_device *vgdev,
 		virtio_gpu_cleanup_object(bo);
 }
 
+int virtio_gpu_cmd_release_resource(struct virtio_gpu_device *vgdev,
+				    struct virtio_gpu_object *bo)
+{
+	struct virtio_gpu_resource_unref *cmd_p;
+	struct virtio_gpu_vbuffer *vbuf;
+
+	cmd_p = virtio_gpu_alloc_cmd(vgdev, &vbuf, sizeof(*cmd_p));
+	memset(cmd_p, 0, sizeof(*cmd_p));
+
+	cmd_p->hdr.type = cpu_to_le32(VIRTIO_GPU_CMD_RESOURCE_UNREF);
+	cmd_p->resource_id = cpu_to_le32(bo->hw_res_handle);
+
+	return virtio_gpu_queue_ctrl_buffer(vgdev, vbuf);
+}
+
 void virtio_gpu_cmd_set_scanout(struct virtio_gpu_device *vgdev,
 				uint32_t scanout_id, uint32_t resource_id,
 				uint32_t width, uint32_t height,
@@ -645,6 +660,23 @@ virtio_gpu_cmd_resource_attach_backing(struct virtio_gpu_device *vgdev,
 	virtio_gpu_queue_fenced_ctrl_buffer(vgdev, vbuf, fence);
 }
 
+static void
+virtio_gpu_cmd_resource_detach_backing(struct virtio_gpu_device *vgdev,
+				       u32 resource_id,
+				       struct virtio_gpu_fence *fence)
+{
+	struct virtio_gpu_resource_attach_backing *cmd_p;
+	struct virtio_gpu_vbuffer *vbuf;
+
+	cmd_p = virtio_gpu_alloc_cmd(vgdev, &vbuf, sizeof(*cmd_p));
+	memset(cmd_p, 0, sizeof(*cmd_p));
+
+	cmd_p->hdr.type = cpu_to_le32(VIRTIO_GPU_CMD_RESOURCE_DETACH_BACKING);
+	cmd_p->resource_id = cpu_to_le32(resource_id);
+
+	virtio_gpu_queue_fenced_ctrl_buffer(vgdev, vbuf, fence);
+}
+
 static void virtio_gpu_cmd_get_display_info_cb(struct virtio_gpu_device *vgdev,
 					       struct virtio_gpu_vbuffer *vbuf)
 {
@@ -1107,6 +1139,14 @@ void virtio_gpu_object_attach(struct virtio_gpu_device *vgdev,
 					       ents, nents, NULL);
 }
 
+void virtio_gpu_object_detach(struct virtio_gpu_device *vgdev,
+			      struct virtio_gpu_object *obj,
+			      struct virtio_gpu_fence *fence)
+{
+	virtio_gpu_cmd_resource_detach_backing(vgdev, obj->hw_res_handle,
+					       fence);
+}
+
 void virtio_gpu_cursor_ping(struct virtio_gpu_device *vgdev,
 			    struct virtio_gpu_output *output)
 {
diff --git a/include/uapi/drm/virtgpu_drm.h b/include/uapi/drm/virtgpu_drm.h
index b1d0e56565bc..4caba71b2740 100644
--- a/include/uapi/drm/virtgpu_drm.h
+++ b/include/uapi/drm/virtgpu_drm.h
@@ -48,6 +48,7 @@ extern "C" {
 #define DRM_VIRTGPU_GET_CAPS  0x09
 #define DRM_VIRTGPU_RESOURCE_CREATE_BLOB 0x0a
 #define DRM_VIRTGPU_CONTEXT_INIT 0x0b
+#define DRM_VIRTGPU_MADVISE 0x0c
 
 #define VIRTGPU_EXECBUF_FENCE_FD_IN	0x01
 #define VIRTGPU_EXECBUF_FENCE_FD_OUT	0x02
@@ -211,6 +212,15 @@ struct drm_virtgpu_context_init {
 	__u64 ctx_set_params;
 };
 
+#define VIRTGPU_MADV_WILLNEED 0
+#define VIRTGPU_MADV_DONTNEED 1
+struct drm_virtgpu_madvise {
+	__u32 bo_handle;
+	__u32 retained; /* out, non-zero if BO can be used */
+	__u32 madv;
+	__u32 pad;
+};
+
 /*
  * Event code that's given when VIRTGPU_CONTEXT_PARAM_POLL_RINGS_MASK is in
  * effect.  The event size is sizeof(drm_event), since there is no additional
@@ -261,6 +271,10 @@ struct drm_virtgpu_context_init {
 	DRM_IOWR(DRM_COMMAND_BASE + DRM_VIRTGPU_CONTEXT_INIT,		\
 		struct drm_virtgpu_context_init)
 
+#define DRM_IOCTL_VIRTGPU_MADVISE \
+	DRM_IOWR(DRM_COMMAND_BASE + DRM_VIRTGPU_MADVISE, \
+		 struct drm_virtgpu_madvise)
+
 #if defined(__cplusplus)
 }
 #endif
-- 
2.41.0

[PATCH v16 20/20] drm/panfrost: Switch to generic memory shrinker

[Dmitry Osipenko]

Replace Panfrost's custom memory shrinker with a common drm-shmem
memory shrinker.

Tested-by: Steven Price <steven.price@arm.com> # Firefly-RK3288
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/panfrost/Makefile             |   1 -
 drivers/gpu/drm/panfrost/panfrost_device.h    |   4 -
 drivers/gpu/drm/panfrost/panfrost_drv.c       |  27 ++--
 drivers/gpu/drm/panfrost/panfrost_gem.c       |  30 ++--
 drivers/gpu/drm/panfrost/panfrost_gem.h       |   9 --
 .../gpu/drm/panfrost/panfrost_gem_shrinker.c  | 129 ------------------
 drivers/gpu/drm/panfrost/panfrost_job.c       |  18 ++-
 include/drm/drm_gem_shmem_helper.h            |   7 -
 8 files changed, 47 insertions(+), 178 deletions(-)
 delete mode 100644 drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c

diff --git a/drivers/gpu/drm/panfrost/Makefile b/drivers/gpu/drm/panfrost/Makefile
index 7da2b3f02ed9..11622e22cf15 100644
--- a/drivers/gpu/drm/panfrost/Makefile
+++ b/drivers/gpu/drm/panfrost/Makefile
@@ -5,7 +5,6 @@ panfrost-y := \
 	panfrost_device.o \
 	panfrost_devfreq.o \
 	panfrost_gem.o \
-	panfrost_gem_shrinker.o \
 	panfrost_gpu.o \
 	panfrost_job.o \
 	panfrost_mmu.o \
diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h
index b0126b9fbadc..dcc2571c092b 100644
--- a/drivers/gpu/drm/panfrost/panfrost_device.h
+++ b/drivers/gpu/drm/panfrost/panfrost_device.h
@@ -116,10 +116,6 @@ struct panfrost_device {
 		atomic_t pending;
 	} reset;
 
-	struct mutex shrinker_lock;
-	struct list_head shrinker_list;
-	struct shrinker shrinker;
-
 	struct panfrost_devfreq pfdevfreq;
 };
 
diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
index 175443eacead..8cf338c2a03b 100644
--- a/drivers/gpu/drm/panfrost/panfrost_drv.c
+++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
@@ -170,7 +170,6 @@ panfrost_lookup_bos(struct drm_device *dev,
 			break;
 		}
 
-		atomic_inc(&bo->gpu_usecount);
 		job->mappings[i] = mapping;
 	}
 
@@ -395,7 +394,6 @@ static int panfrost_ioctl_madvise(struct drm_device *dev, void *data,
 {
 	struct panfrost_file_priv *priv = file_priv->driver_priv;
 	struct drm_panfrost_madvise *args = data;
-	struct panfrost_device *pfdev = dev->dev_private;
 	struct drm_gem_object *gem_obj;
 	struct panfrost_gem_object *bo;
 	int ret = 0;
@@ -408,11 +406,15 @@ static int panfrost_ioctl_madvise(struct drm_device *dev, void *data,
 
 	bo = to_panfrost_bo(gem_obj);
 
+	if (bo->is_heap) {
+		args->retained = 1;
+		goto out_put_object;
+	}
+
 	ret = dma_resv_lock_interruptible(bo->base.base.resv, NULL);
 	if (ret)
 		goto out_put_object;
 
-	mutex_lock(&pfdev->shrinker_lock);
 	mutex_lock(&bo->mappings.lock);
 	if (args->madv == PANFROST_MADV_DONTNEED) {
 		struct panfrost_gem_mapping *first;
@@ -438,17 +440,8 @@ static int panfrost_ioctl_madvise(struct drm_device *dev, void *data,
 
 	args->retained = drm_gem_shmem_madvise_locked(&bo->base, args->madv);
 
-	if (args->retained) {
-		if (args->madv == PANFROST_MADV_DONTNEED)
-			list_move_tail(&bo->base.madv_list,
-				       &pfdev->shrinker_list);
-		else if (args->madv == PANFROST_MADV_WILLNEED)
-			list_del_init(&bo->base.madv_list);
-	}
-
 out_unlock_mappings:
 	mutex_unlock(&bo->mappings.lock);
-	mutex_unlock(&pfdev->shrinker_lock);
 	dma_resv_unlock(bo->base.base.resv);
 out_put_object:
 	drm_gem_object_put(gem_obj);
@@ -577,9 +570,6 @@ static int panfrost_probe(struct platform_device *pdev)
 	ddev->dev_private = pfdev;
 	pfdev->ddev = ddev;
 
-	mutex_init(&pfdev->shrinker_lock);
-	INIT_LIST_HEAD(&pfdev->shrinker_list);
-
 	err = panfrost_device_init(pfdev);
 	if (err) {
 		if (err != -EPROBE_DEFER)
@@ -601,10 +591,14 @@ static int panfrost_probe(struct platform_device *pdev)
 	if (err < 0)
 		goto err_out1;
 
-	panfrost_gem_shrinker_init(ddev);
+	err = drmm_gem_shmem_init(ddev);
+	if (err < 0)
+		goto err_out2;
 
 	return 0;
 
+err_out2:
+	drm_dev_unregister(ddev);
 err_out1:
 	pm_runtime_disable(pfdev->dev);
 	panfrost_device_fini(pfdev);
@@ -620,7 +614,6 @@ static void panfrost_remove(struct platform_device *pdev)
 	struct drm_device *ddev = pfdev->ddev;
 
 	drm_dev_unregister(ddev);
-	panfrost_gem_shrinker_cleanup(ddev);
 
 	pm_runtime_get_sync(pfdev->dev);
 	pm_runtime_disable(pfdev->dev);
diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
index 59c8c73c6a59..00165fca7f3d 100644
--- a/drivers/gpu/drm/panfrost/panfrost_gem.c
+++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
@@ -19,16 +19,6 @@ static void panfrost_gem_free_object(struct drm_gem_object *obj)
 	struct panfrost_gem_object *bo = to_panfrost_bo(obj);
 	struct panfrost_device *pfdev = obj->dev->dev_private;
 
-	/*
-	 * Make sure the BO is no longer inserted in the shrinker list before
-	 * taking care of the destruction itself. If we don't do that we have a
-	 * race condition between this function and what's done in
-	 * panfrost_gem_shrinker_scan().
-	 */
-	mutex_lock(&pfdev->shrinker_lock);
-	list_del_init(&bo->base.madv_list);
-	mutex_unlock(&pfdev->shrinker_lock);
-
 	/*
 	 * If we still have mappings attached to the BO, there's a problem in
 	 * our refcounting.
@@ -195,6 +185,25 @@ static int panfrost_gem_pin(struct drm_gem_object *obj)
 	return drm_gem_shmem_object_pin(obj);
 }
 
+static int panfrost_shmem_evict(struct drm_gem_object *obj)
+{
+	struct panfrost_gem_object *bo = to_panfrost_bo(obj);
+
+	if (!drm_gem_shmem_is_purgeable(&bo->base))
+		return -EBUSY;
+
+	if (!mutex_trylock(&bo->mappings.lock))
+		return -EBUSY;
+
+	panfrost_gem_teardown_mappings_locked(bo);
+
+	drm_gem_shmem_purge_locked(&bo->base);
+
+	mutex_unlock(&bo->mappings.lock);
+
+	return 0;
+}
+
 static const struct drm_gem_object_funcs panfrost_gem_funcs = {
 	.free = panfrost_gem_free_object,
 	.open = panfrost_gem_open,
@@ -207,6 +216,7 @@ static const struct drm_gem_object_funcs panfrost_gem_funcs = {
 	.vunmap = drm_gem_shmem_object_vunmap_locked,
 	.mmap = drm_gem_shmem_object_mmap,
 	.vm_ops = &drm_gem_shmem_vm_ops,
+	.evict = panfrost_shmem_evict,
 };
 
 /**
diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.h b/drivers/gpu/drm/panfrost/panfrost_gem.h
index ad2877eeeccd..6ad1bcedb932 100644
--- a/drivers/gpu/drm/panfrost/panfrost_gem.h
+++ b/drivers/gpu/drm/panfrost/panfrost_gem.h
@@ -30,12 +30,6 @@ struct panfrost_gem_object {
 		struct mutex lock;
 	} mappings;
 
-	/*
-	 * Count the number of jobs referencing this BO so we don't let the
-	 * shrinker reclaim this object prematurely.
-	 */
-	atomic_t gpu_usecount;
-
 	bool noexec		:1;
 	bool is_heap		:1;
 };
@@ -81,7 +75,4 @@ panfrost_gem_mapping_get(struct panfrost_gem_object *bo,
 void panfrost_gem_mapping_put(struct panfrost_gem_mapping *mapping);
 void panfrost_gem_teardown_mappings_locked(struct panfrost_gem_object *bo);
 
-void panfrost_gem_shrinker_init(struct drm_device *dev);
-void panfrost_gem_shrinker_cleanup(struct drm_device *dev);
-
 #endif /* __PANFROST_GEM_H__ */
diff --git a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
deleted file mode 100644
index 1aa94fff7072..000000000000
--- a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
+++ /dev/null
@@ -1,129 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/* Copyright (C) 2019 Arm Ltd.
- *
- * Based on msm_gem_freedreno.c:
- * Copyright (C) 2016 Red Hat
- * Author: Rob Clark <robdclark@gmail.com>
- */
-
-#include <linux/list.h>
-
-#include <drm/drm_device.h>
-#include <drm/drm_gem_shmem_helper.h>
-
-#include "panfrost_device.h"
-#include "panfrost_gem.h"
-#include "panfrost_mmu.h"
-
-static bool panfrost_gem_shmem_is_purgeable(struct drm_gem_shmem_object *shmem)
-{
-	return (shmem->madv > 0) &&
-		!refcount_read(&shmem->pages_pin_count) && shmem->sgt &&
-		!shmem->base.dma_buf && !shmem->base.import_attach;
-}
-
-static unsigned long
-panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
-{
-	struct panfrost_device *pfdev =
-		container_of(shrinker, struct panfrost_device, shrinker);
-	struct drm_gem_shmem_object *shmem;
-	unsigned long count = 0;
-
-	if (!mutex_trylock(&pfdev->shrinker_lock))
-		return 0;
-
-	list_for_each_entry(shmem, &pfdev->shrinker_list, madv_list) {
-		if (panfrost_gem_shmem_is_purgeable(shmem))
-			count += shmem->base.size >> PAGE_SHIFT;
-	}
-
-	mutex_unlock(&pfdev->shrinker_lock);
-
-	return count;
-}
-
-static bool panfrost_gem_purge(struct drm_gem_object *obj)
-{
-	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
-	struct panfrost_gem_object *bo = to_panfrost_bo(obj);
-	bool ret = false;
-
-	if (atomic_read(&bo->gpu_usecount))
-		return false;
-
-	if (!mutex_trylock(&bo->mappings.lock))
-		return false;
-
-	if (!dma_resv_trylock(shmem->base.resv))
-		goto unlock_mappings;
-
-	panfrost_gem_teardown_mappings_locked(bo);
-	drm_gem_shmem_purge_locked(&bo->base);
-	ret = true;
-
-	dma_resv_unlock(shmem->base.resv);
-
-unlock_mappings:
-	mutex_unlock(&bo->mappings.lock);
-	return ret;
-}
-
-static unsigned long
-panfrost_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
-{
-	struct panfrost_device *pfdev =
-		container_of(shrinker, struct panfrost_device, shrinker);
-	struct drm_gem_shmem_object *shmem, *tmp;
-	unsigned long freed = 0;
-
-	if (!mutex_trylock(&pfdev->shrinker_lock))
-		return SHRINK_STOP;
-
-	list_for_each_entry_safe(shmem, tmp, &pfdev->shrinker_list, madv_list) {
-		if (freed >= sc->nr_to_scan)
-			break;
-		if (drm_gem_shmem_is_purgeable(shmem) &&
-		    panfrost_gem_purge(&shmem->base)) {
-			freed += shmem->base.size >> PAGE_SHIFT;
-			list_del_init(&shmem->madv_list);
-		}
-	}
-
-	mutex_unlock(&pfdev->shrinker_lock);
-
-	if (freed > 0)
-		pr_info_ratelimited("Purging %lu bytes\n", freed << PAGE_SHIFT);
-
-	return freed;
-}
-
-/**
- * panfrost_gem_shrinker_init - Initialize panfrost shrinker
- * @dev: DRM device
- *
- * This function registers and sets up the panfrost shrinker.
- */
-void panfrost_gem_shrinker_init(struct drm_device *dev)
-{
-	struct panfrost_device *pfdev = dev->dev_private;
-	pfdev->shrinker.count_objects = panfrost_gem_shrinker_count;
-	pfdev->shrinker.scan_objects = panfrost_gem_shrinker_scan;
-	pfdev->shrinker.seeks = DEFAULT_SEEKS;
-	WARN_ON(register_shrinker(&pfdev->shrinker, "drm-panfrost"));
-}
-
-/**
- * panfrost_gem_shrinker_cleanup - Clean up panfrost shrinker
- * @dev: DRM device
- *
- * This function unregisters the panfrost shrinker.
- */
-void panfrost_gem_shrinker_cleanup(struct drm_device *dev)
-{
-	struct panfrost_device *pfdev = dev->dev_private;
-
-	if (pfdev->shrinker.nr_deferred) {
-		unregister_shrinker(&pfdev->shrinker);
-	}
-}
diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
index a8b4827dc425..755128eb6c45 100644
--- a/drivers/gpu/drm/panfrost/panfrost_job.c
+++ b/drivers/gpu/drm/panfrost/panfrost_job.c
@@ -272,6 +272,19 @@ static void panfrost_attach_object_fences(struct drm_gem_object **bos,
 		dma_resv_add_fence(bos[i]->resv, fence, DMA_RESV_USAGE_WRITE);
 }
 
+static int panfrost_objects_prepare(struct drm_gem_object **bos, int bo_count)
+{
+	struct panfrost_gem_object *bo;
+	int ret = 0;
+
+	while (!ret && bo_count--) {
+		bo = to_panfrost_bo(bos[bo_count]);
+		ret = bo->base.madv ? -ENOMEM : 0;
+	}
+
+	return ret;
+}
+
 int panfrost_job_push(struct panfrost_job *job)
 {
 	struct panfrost_device *pfdev = job->pfdev;
@@ -283,6 +296,10 @@ int panfrost_job_push(struct panfrost_job *job)
 	if (ret)
 		return ret;
 
+	ret = panfrost_objects_prepare(job->bos, job->bo_count);
+	if (ret)
+		goto unlock;
+
 	mutex_lock(&pfdev->sched_lock);
 	drm_sched_job_arm(&job->base);
 
@@ -324,7 +341,6 @@ static void panfrost_job_cleanup(struct kref *ref)
 			if (!job->mappings[i])
 				break;
 
-			atomic_dec(&job->mappings[i]->obj->gpu_usecount);
 			panfrost_gem_mapping_put(job->mappings[i]);
 		}
 		kvfree(job->mappings);
diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
index 2d7debc23ac1..13fe34236a0b 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -60,13 +60,6 @@ struct drm_gem_shmem_object {
 	 */
 	int madv;
 
-	/**
-	 * @madv_list: List entry for madvise tracking
-	 *
-	 * Typically used by drivers to track purgeable objects
-	 */
-	struct list_head madv_list;
-
 	/**
 	 * @sgt: Scatter/gather table for imported PRIME buffers
 	 */
-- 
2.41.0

Re: [PATCH v16 20/20] drm/panfrost: Switch to generic memory shrinker

[Steven Price]

On 03/09/2023 18:07, Dmitry Osipenko wrote:
> Replace Panfrost's custom memory shrinker with a common drm-shmem
> memory shrinker.
> 
> Tested-by: Steven Price <steven.price@arm.com> # Firefly-RK3288

I just gave this version of the series a spin and I can trigger the following 
warning:

[  477.776163] ------------[ cut here ]------------
[  477.781353] WARNING: CPU: 0 PID: 292 at drivers/gpu/drm/drm_gem_shmem_helper.c:227 drm_gem_shmem_free+0x1fc/0x200 [drm_shmem_helper]
[  477.794790] panfrost ffa30000.gpu: drm_WARN_ON(refcount_read(&shmem->pages_use_count))
[  477.794797] Modules linked in: panfrost gpu_sched drm_shmem_helper
[  477.810942] CPU: 0 PID: 292 Comm: glmark2-es2-drm Not tainted 6.5.0-rc2-00527-gc8a0c16fa830 #1
[  477.820564] Hardware name: Rockchip (Device Tree)
[  477.825820]  unwind_backtrace from show_stack+0x10/0x14
[  477.831670]  show_stack from dump_stack_lvl+0x58/0x70
[  477.837319]  dump_stack_lvl from __warn+0x7c/0x1a4
[  477.842680]  __warn from warn_slowpath_fmt+0x134/0x1a0
[  477.848429]  warn_slowpath_fmt from drm_gem_shmem_free+0x1fc/0x200 [drm_shmem_helper]
[  477.857199]  drm_gem_shmem_free [drm_shmem_helper] from drm_gem_handle_delete+0x84/0xb0
[  477.866163]  drm_gem_handle_delete from drm_ioctl+0x214/0x4ec
[  477.872592]  drm_ioctl from sys_ioctl+0x568/0xd48
[  477.877857]  sys_ioctl from ret_fast_syscall+0x0/0x1c
[  477.883504] Exception stack(0xf0a49fa8 to 0xf0a49ff0)
[  477.889148] 9fa0:                   005969c0 bef34880 00000006 40086409 bef34880 00000001
[  477.898289] 9fc0: 005969c0 bef34880 40086409 00000036 bef34880 00590b64 00590aec 00000000
[  477.907428] 9fe0: b6ec408c bef3485c b6ead42f b6c31f98
[  477.913188] irq event stamp: 37296889
[  477.917319] hardirqs last  enabled at (37296951): [<c03c1968>] __up_console_sem+0x50/0x60
[  477.926531] hardirqs last disabled at (37296972): [<c03c1954>] __up_console_sem+0x3c/0x60
[  477.935714] softirqs last  enabled at (37296986): [<c03016cc>] __do_softirq+0x318/0x4d4
[  477.944708] softirqs last disabled at (37296981): [<c034f9ec>] __irq_exit_rcu+0x140/0x160
[  477.953878] ---[ end trace 0000000000000000 ]---

So something, somewhere has gone wrong with the reference counts.

Steve

> Reviewed-by: Steven Price <steven.price@arm.com>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> ---
>  drivers/gpu/drm/panfrost/Makefile             |   1 -
>  drivers/gpu/drm/panfrost/panfrost_device.h    |   4 -
>  drivers/gpu/drm/panfrost/panfrost_drv.c       |  27 ++--
>  drivers/gpu/drm/panfrost/panfrost_gem.c       |  30 ++--
>  drivers/gpu/drm/panfrost/panfrost_gem.h       |   9 --
>  .../gpu/drm/panfrost/panfrost_gem_shrinker.c  | 129 ------------------
>  drivers/gpu/drm/panfrost/panfrost_job.c       |  18 ++-
>  include/drm/drm_gem_shmem_helper.h            |   7 -
>  8 files changed, 47 insertions(+), 178 deletions(-)
>  delete mode 100644 drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
> 
> diff --git a/drivers/gpu/drm/panfrost/Makefile b/drivers/gpu/drm/panfrost/Makefile
> index 7da2b3f02ed9..11622e22cf15 100644
> --- a/drivers/gpu/drm/panfrost/Makefile
> +++ b/drivers/gpu/drm/panfrost/Makefile
> @@ -5,7 +5,6 @@ panfrost-y := \
>  	panfrost_device.o \
>  	panfrost_devfreq.o \
>  	panfrost_gem.o \
> -	panfrost_gem_shrinker.o \
>  	panfrost_gpu.o \
>  	panfrost_job.o \
>  	panfrost_mmu.o \
> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h
> index b0126b9fbadc..dcc2571c092b 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_device.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_device.h
> @@ -116,10 +116,6 @@ struct panfrost_device {
>  		atomic_t pending;
>  	} reset;
>  
> -	struct mutex shrinker_lock;
> -	struct list_head shrinker_list;
> -	struct shrinker shrinker;
> -
>  	struct panfrost_devfreq pfdevfreq;
>  };
>  
> diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
> index 175443eacead..8cf338c2a03b 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_drv.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
> @@ -170,7 +170,6 @@ panfrost_lookup_bos(struct drm_device *dev,
>  			break;
>  		}
>  
> -		atomic_inc(&bo->gpu_usecount);
>  		job->mappings[i] = mapping;
>  	}
>  
> @@ -395,7 +394,6 @@ static int panfrost_ioctl_madvise(struct drm_device *dev, void *data,
>  {
>  	struct panfrost_file_priv *priv = file_priv->driver_priv;
>  	struct drm_panfrost_madvise *args = data;
> -	struct panfrost_device *pfdev = dev->dev_private;
>  	struct drm_gem_object *gem_obj;
>  	struct panfrost_gem_object *bo;
>  	int ret = 0;
> @@ -408,11 +406,15 @@ static int panfrost_ioctl_madvise(struct drm_device *dev, void *data,
>  
>  	bo = to_panfrost_bo(gem_obj);
>  
> +	if (bo->is_heap) {
> +		args->retained = 1;
> +		goto out_put_object;
> +	}
> +
>  	ret = dma_resv_lock_interruptible(bo->base.base.resv, NULL);
>  	if (ret)
>  		goto out_put_object;
>  
> -	mutex_lock(&pfdev->shrinker_lock);
>  	mutex_lock(&bo->mappings.lock);
>  	if (args->madv == PANFROST_MADV_DONTNEED) {
>  		struct panfrost_gem_mapping *first;
> @@ -438,17 +440,8 @@ static int panfrost_ioctl_madvise(struct drm_device *dev, void *data,
>  
>  	args->retained = drm_gem_shmem_madvise_locked(&bo->base, args->madv);
>  
> -	if (args->retained) {
> -		if (args->madv == PANFROST_MADV_DONTNEED)
> -			list_move_tail(&bo->base.madv_list,
> -				       &pfdev->shrinker_list);
> -		else if (args->madv == PANFROST_MADV_WILLNEED)
> -			list_del_init(&bo->base.madv_list);
> -	}
> -
>  out_unlock_mappings:
>  	mutex_unlock(&bo->mappings.lock);
> -	mutex_unlock(&pfdev->shrinker_lock);
>  	dma_resv_unlock(bo->base.base.resv);
>  out_put_object:
>  	drm_gem_object_put(gem_obj);
> @@ -577,9 +570,6 @@ static int panfrost_probe(struct platform_device *pdev)
>  	ddev->dev_private = pfdev;
>  	pfdev->ddev = ddev;
>  
> -	mutex_init(&pfdev->shrinker_lock);
> -	INIT_LIST_HEAD(&pfdev->shrinker_list);
> -
>  	err = panfrost_device_init(pfdev);
>  	if (err) {
>  		if (err != -EPROBE_DEFER)
> @@ -601,10 +591,14 @@ static int panfrost_probe(struct platform_device *pdev)
>  	if (err < 0)
>  		goto err_out1;
>  
> -	panfrost_gem_shrinker_init(ddev);
> +	err = drmm_gem_shmem_init(ddev);
> +	if (err < 0)
> +		goto err_out2;
>  
>  	return 0;
>  
> +err_out2:
> +	drm_dev_unregister(ddev);
>  err_out1:
>  	pm_runtime_disable(pfdev->dev);
>  	panfrost_device_fini(pfdev);
> @@ -620,7 +614,6 @@ static void panfrost_remove(struct platform_device *pdev)
>  	struct drm_device *ddev = pfdev->ddev;
>  
>  	drm_dev_unregister(ddev);
> -	panfrost_gem_shrinker_cleanup(ddev);
>  
>  	pm_runtime_get_sync(pfdev->dev);
>  	pm_runtime_disable(pfdev->dev);
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
> index 59c8c73c6a59..00165fca7f3d 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gem.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
> @@ -19,16 +19,6 @@ static void panfrost_gem_free_object(struct drm_gem_object *obj)
>  	struct panfrost_gem_object *bo = to_panfrost_bo(obj);
>  	struct panfrost_device *pfdev = obj->dev->dev_private;
>  
> -	/*
> -	 * Make sure the BO is no longer inserted in the shrinker list before
> -	 * taking care of the destruction itself. If we don't do that we have a
> -	 * race condition between this function and what's done in
> -	 * panfrost_gem_shrinker_scan().
> -	 */
> -	mutex_lock(&pfdev->shrinker_lock);
> -	list_del_init(&bo->base.madv_list);
> -	mutex_unlock(&pfdev->shrinker_lock);
> -
>  	/*
>  	 * If we still have mappings attached to the BO, there's a problem in
>  	 * our refcounting.
> @@ -195,6 +185,25 @@ static int panfrost_gem_pin(struct drm_gem_object *obj)
>  	return drm_gem_shmem_object_pin(obj);
>  }
>  
> +static int panfrost_shmem_evict(struct drm_gem_object *obj)
> +{
> +	struct panfrost_gem_object *bo = to_panfrost_bo(obj);
> +
> +	if (!drm_gem_shmem_is_purgeable(&bo->base))
> +		return -EBUSY;
> +
> +	if (!mutex_trylock(&bo->mappings.lock))
> +		return -EBUSY;
> +
> +	panfrost_gem_teardown_mappings_locked(bo);
> +
> +	drm_gem_shmem_purge_locked(&bo->base);
> +
> +	mutex_unlock(&bo->mappings.lock);
> +
> +	return 0;
> +}
> +
>  static const struct drm_gem_object_funcs panfrost_gem_funcs = {
>  	.free = panfrost_gem_free_object,
>  	.open = panfrost_gem_open,
> @@ -207,6 +216,7 @@ static const struct drm_gem_object_funcs panfrost_gem_funcs = {
>  	.vunmap = drm_gem_shmem_object_vunmap_locked,
>  	.mmap = drm_gem_shmem_object_mmap,
>  	.vm_ops = &drm_gem_shmem_vm_ops,
> +	.evict = panfrost_shmem_evict,
>  };
>  
>  /**
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.h b/drivers/gpu/drm/panfrost/panfrost_gem.h
> index ad2877eeeccd..6ad1bcedb932 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gem.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.h
> @@ -30,12 +30,6 @@ struct panfrost_gem_object {
>  		struct mutex lock;
>  	} mappings;
>  
> -	/*
> -	 * Count the number of jobs referencing this BO so we don't let the
> -	 * shrinker reclaim this object prematurely.
> -	 */
> -	atomic_t gpu_usecount;
> -
>  	bool noexec		:1;
>  	bool is_heap		:1;
>  };
> @@ -81,7 +75,4 @@ panfrost_gem_mapping_get(struct panfrost_gem_object *bo,
>  void panfrost_gem_mapping_put(struct panfrost_gem_mapping *mapping);
>  void panfrost_gem_teardown_mappings_locked(struct panfrost_gem_object *bo);
>  
> -void panfrost_gem_shrinker_init(struct drm_device *dev);
> -void panfrost_gem_shrinker_cleanup(struct drm_device *dev);
> -
>  #endif /* __PANFROST_GEM_H__ */
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
> deleted file mode 100644
> index 1aa94fff7072..000000000000
> --- a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
> +++ /dev/null
> @@ -1,129 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0
> -/* Copyright (C) 2019 Arm Ltd.
> - *
> - * Based on msm_gem_freedreno.c:
> - * Copyright (C) 2016 Red Hat
> - * Author: Rob Clark <robdclark@gmail.com>
> - */
> -
> -#include <linux/list.h>
> -
> -#include <drm/drm_device.h>
> -#include <drm/drm_gem_shmem_helper.h>
> -
> -#include "panfrost_device.h"
> -#include "panfrost_gem.h"
> -#include "panfrost_mmu.h"
> -
> -static bool panfrost_gem_shmem_is_purgeable(struct drm_gem_shmem_object *shmem)
> -{
> -	return (shmem->madv > 0) &&
> -		!refcount_read(&shmem->pages_pin_count) && shmem->sgt &&
> -		!shmem->base.dma_buf && !shmem->base.import_attach;
> -}
> -
> -static unsigned long
> -panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
> -{
> -	struct panfrost_device *pfdev =
> -		container_of(shrinker, struct panfrost_device, shrinker);
> -	struct drm_gem_shmem_object *shmem;
> -	unsigned long count = 0;
> -
> -	if (!mutex_trylock(&pfdev->shrinker_lock))
> -		return 0;
> -
> -	list_for_each_entry(shmem, &pfdev->shrinker_list, madv_list) {
> -		if (panfrost_gem_shmem_is_purgeable(shmem))
> -			count += shmem->base.size >> PAGE_SHIFT;
> -	}
> -
> -	mutex_unlock(&pfdev->shrinker_lock);
> -
> -	return count;
> -}
> -
> -static bool panfrost_gem_purge(struct drm_gem_object *obj)
> -{
> -	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> -	struct panfrost_gem_object *bo = to_panfrost_bo(obj);
> -	bool ret = false;
> -
> -	if (atomic_read(&bo->gpu_usecount))
> -		return false;
> -
> -	if (!mutex_trylock(&bo->mappings.lock))
> -		return false;
> -
> -	if (!dma_resv_trylock(shmem->base.resv))
> -		goto unlock_mappings;
> -
> -	panfrost_gem_teardown_mappings_locked(bo);
> -	drm_gem_shmem_purge_locked(&bo->base);
> -	ret = true;
> -
> -	dma_resv_unlock(shmem->base.resv);
> -
> -unlock_mappings:
> -	mutex_unlock(&bo->mappings.lock);
> -	return ret;
> -}
> -
> -static unsigned long
> -panfrost_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
> -{
> -	struct panfrost_device *pfdev =
> -		container_of(shrinker, struct panfrost_device, shrinker);
> -	struct drm_gem_shmem_object *shmem, *tmp;
> -	unsigned long freed = 0;
> -
> -	if (!mutex_trylock(&pfdev->shrinker_lock))
> -		return SHRINK_STOP;
> -
> -	list_for_each_entry_safe(shmem, tmp, &pfdev->shrinker_list, madv_list) {
> -		if (freed >= sc->nr_to_scan)
> -			break;
> -		if (drm_gem_shmem_is_purgeable(shmem) &&
> -		    panfrost_gem_purge(&shmem->base)) {
> -			freed += shmem->base.size >> PAGE_SHIFT;
> -			list_del_init(&shmem->madv_list);
> -		}
> -	}
> -
> -	mutex_unlock(&pfdev->shrinker_lock);
> -
> -	if (freed > 0)
> -		pr_info_ratelimited("Purging %lu bytes\n", freed << PAGE_SHIFT);
> -
> -	return freed;
> -}
> -
> -/**
> - * panfrost_gem_shrinker_init - Initialize panfrost shrinker
> - * @dev: DRM device
> - *
> - * This function registers and sets up the panfrost shrinker.
> - */
> -void panfrost_gem_shrinker_init(struct drm_device *dev)
> -{
> -	struct panfrost_device *pfdev = dev->dev_private;
> -	pfdev->shrinker.count_objects = panfrost_gem_shrinker_count;
> -	pfdev->shrinker.scan_objects = panfrost_gem_shrinker_scan;
> -	pfdev->shrinker.seeks = DEFAULT_SEEKS;
> -	WARN_ON(register_shrinker(&pfdev->shrinker, "drm-panfrost"));
> -}
> -
> -/**
> - * panfrost_gem_shrinker_cleanup - Clean up panfrost shrinker
> - * @dev: DRM device
> - *
> - * This function unregisters the panfrost shrinker.
> - */
> -void panfrost_gem_shrinker_cleanup(struct drm_device *dev)
> -{
> -	struct panfrost_device *pfdev = dev->dev_private;
> -
> -	if (pfdev->shrinker.nr_deferred) {
> -		unregister_shrinker(&pfdev->shrinker);
> -	}
> -}
> diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
> index a8b4827dc425..755128eb6c45 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_job.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
> @@ -272,6 +272,19 @@ static void panfrost_attach_object_fences(struct drm_gem_object **bos,
>  		dma_resv_add_fence(bos[i]->resv, fence, DMA_RESV_USAGE_WRITE);
>  }
>  
> +static int panfrost_objects_prepare(struct drm_gem_object **bos, int bo_count)
> +{
> +	struct panfrost_gem_object *bo;
> +	int ret = 0;
> +
> +	while (!ret && bo_count--) {
> +		bo = to_panfrost_bo(bos[bo_count]);
> +		ret = bo->base.madv ? -ENOMEM : 0;
> +	}
> +
> +	return ret;
> +}
> +
>  int panfrost_job_push(struct panfrost_job *job)
>  {
>  	struct panfrost_device *pfdev = job->pfdev;
> @@ -283,6 +296,10 @@ int panfrost_job_push(struct panfrost_job *job)
>  	if (ret)
>  		return ret;
>  
> +	ret = panfrost_objects_prepare(job->bos, job->bo_count);
> +	if (ret)
> +		goto unlock;
> +
>  	mutex_lock(&pfdev->sched_lock);
>  	drm_sched_job_arm(&job->base);
>  
> @@ -324,7 +341,6 @@ static void panfrost_job_cleanup(struct kref *ref)
>  			if (!job->mappings[i])
>  				break;
>  
> -			atomic_dec(&job->mappings[i]->obj->gpu_usecount);
>  			panfrost_gem_mapping_put(job->mappings[i]);
>  		}
>  		kvfree(job->mappings);
> diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
> index 2d7debc23ac1..13fe34236a0b 100644
> --- a/include/drm/drm_gem_shmem_helper.h
> +++ b/include/drm/drm_gem_shmem_helper.h
> @@ -60,13 +60,6 @@ struct drm_gem_shmem_object {
>  	 */
>  	int madv;
>  
> -	/**
> -	 * @madv_list: List entry for madvise tracking
> -	 *
> -	 * Typically used by drivers to track purgeable objects
> -	 */
> -	struct list_head madv_list;
> -
>  	/**
>  	 * @sgt: Scatter/gather table for imported PRIME buffers
>  	 */

Re: [PATCH v16 20/20] drm/panfrost: Switch to generic memory shrinker

[Boris Brezillon]

On Mon, 4 Sep 2023 14:20:24 +0100
Steven Price <steven.price@arm.com> wrote:

> On 03/09/2023 18:07, Dmitry Osipenko wrote:
> > Replace Panfrost's custom memory shrinker with a common drm-shmem
> > memory shrinker.
> > 
> > Tested-by: Steven Price <steven.price@arm.com> # Firefly-RK3288  
> 
> I just gave this version of the series a spin and I can trigger the following 
> warning:
> 
> [  477.776163] ------------[ cut here ]------------
> [  477.781353] WARNING: CPU: 0 PID: 292 at drivers/gpu/drm/drm_gem_shmem_helper.c:227 drm_gem_shmem_free+0x1fc/0x200 [drm_shmem_helper]
> [  477.794790] panfrost ffa30000.gpu: drm_WARN_ON(refcount_read(&shmem->pages_use_count))
> [  477.794797] Modules linked in: panfrost gpu_sched drm_shmem_helper
> [  477.810942] CPU: 0 PID: 292 Comm: glmark2-es2-drm Not tainted 6.5.0-rc2-00527-gc8a0c16fa830 #1
> [  477.820564] Hardware name: Rockchip (Device Tree)
> [  477.825820]  unwind_backtrace from show_stack+0x10/0x14
> [  477.831670]  show_stack from dump_stack_lvl+0x58/0x70
> [  477.837319]  dump_stack_lvl from __warn+0x7c/0x1a4
> [  477.842680]  __warn from warn_slowpath_fmt+0x134/0x1a0
> [  477.848429]  warn_slowpath_fmt from drm_gem_shmem_free+0x1fc/0x200 [drm_shmem_helper]
> [  477.857199]  drm_gem_shmem_free [drm_shmem_helper] from drm_gem_handle_delete+0x84/0xb0
> [  477.866163]  drm_gem_handle_delete from drm_ioctl+0x214/0x4ec
> [  477.872592]  drm_ioctl from sys_ioctl+0x568/0xd48
> [  477.877857]  sys_ioctl from ret_fast_syscall+0x0/0x1c
> [  477.883504] Exception stack(0xf0a49fa8 to 0xf0a49ff0)
> [  477.889148] 9fa0:                   005969c0 bef34880 00000006 40086409 bef34880 00000001
> [  477.898289] 9fc0: 005969c0 bef34880 40086409 00000036 bef34880 00590b64 00590aec 00000000
> [  477.907428] 9fe0: b6ec408c bef3485c b6ead42f b6c31f98
> [  477.913188] irq event stamp: 37296889
> [  477.917319] hardirqs last  enabled at (37296951): [<c03c1968>] __up_console_sem+0x50/0x60
> [  477.926531] hardirqs last disabled at (37296972): [<c03c1954>] __up_console_sem+0x3c/0x60
> [  477.935714] softirqs last  enabled at (37296986): [<c03016cc>] __do_softirq+0x318/0x4d4
> [  477.944708] softirqs last disabled at (37296981): [<c034f9ec>] __irq_exit_rcu+0x140/0x160
> [  477.953878] ---[ end trace 0000000000000000 ]---
> 
> So something, somewhere has gone wrong with the reference counts.

Missing `got_pages_sgt = true;` in the fault handler, when creating the
sgt and populating the first 2MB chunk, I guess (should have been part
of "drm/shmem-helper: Use flag for tracking page count bumped by
get_pages_sgt()"). This kinda proves my point though: adding flags
for things that can be inferred from other fields is a bad idea, because
there's always the risk of not updating all the places that are manually
filling these other fields...

> 
> Steve
> 
> > Reviewed-by: Steven Price <steven.price@arm.com>
> > Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> > ---
> >  drivers/gpu/drm/panfrost/Makefile             |   1 -
> >  drivers/gpu/drm/panfrost/panfrost_device.h    |   4 -
> >  drivers/gpu/drm/panfrost/panfrost_drv.c       |  27 ++--
> >  drivers/gpu/drm/panfrost/panfrost_gem.c       |  30 ++--
> >  drivers/gpu/drm/panfrost/panfrost_gem.h       |   9 --
> >  .../gpu/drm/panfrost/panfrost_gem_shrinker.c  | 129 ------------------
> >  drivers/gpu/drm/panfrost/panfrost_job.c       |  18 ++-
> >  include/drm/drm_gem_shmem_helper.h            |   7 -
> >  8 files changed, 47 insertions(+), 178 deletions(-)
> >  delete mode 100644 drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
> > 
> > diff --git a/drivers/gpu/drm/panfrost/Makefile b/drivers/gpu/drm/panfrost/Makefile
> > index 7da2b3f02ed9..11622e22cf15 100644
> > --- a/drivers/gpu/drm/panfrost/Makefile
> > +++ b/drivers/gpu/drm/panfrost/Makefile
> > @@ -5,7 +5,6 @@ panfrost-y := \
> >  	panfrost_device.o \
> >  	panfrost_devfreq.o \
> >  	panfrost_gem.o \
> > -	panfrost_gem_shrinker.o \
> >  	panfrost_gpu.o \
> >  	panfrost_job.o \
> >  	panfrost_mmu.o \
> > diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h
> > index b0126b9fbadc..dcc2571c092b 100644
> > --- a/drivers/gpu/drm/panfrost/panfrost_device.h
> > +++ b/drivers/gpu/drm/panfrost/panfrost_device.h
> > @@ -116,10 +116,6 @@ struct panfrost_device {
> >  		atomic_t pending;
> >  	} reset;
> >  
> > -	struct mutex shrinker_lock;
> > -	struct list_head shrinker_list;
> > -	struct shrinker shrinker;
> > -
> >  	struct panfrost_devfreq pfdevfreq;
> >  };
> >  
> > diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
> > index 175443eacead..8cf338c2a03b 100644
> > --- a/drivers/gpu/drm/panfrost/panfrost_drv.c
> > +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
> > @@ -170,7 +170,6 @@ panfrost_lookup_bos(struct drm_device *dev,
> >  			break;
> >  		}
> >  
> > -		atomic_inc(&bo->gpu_usecount);
> >  		job->mappings[i] = mapping;
> >  	}
> >  
> > @@ -395,7 +394,6 @@ static int panfrost_ioctl_madvise(struct drm_device *dev, void *data,
> >  {
> >  	struct panfrost_file_priv *priv = file_priv->driver_priv;
> >  	struct drm_panfrost_madvise *args = data;
> > -	struct panfrost_device *pfdev = dev->dev_private;
> >  	struct drm_gem_object *gem_obj;
> >  	struct panfrost_gem_object *bo;
> >  	int ret = 0;
> > @@ -408,11 +406,15 @@ static int panfrost_ioctl_madvise(struct drm_device *dev, void *data,
> >  
> >  	bo = to_panfrost_bo(gem_obj);
> >  
> > +	if (bo->is_heap) {
> > +		args->retained = 1;
> > +		goto out_put_object;
> > +	}
> > +
> >  	ret = dma_resv_lock_interruptible(bo->base.base.resv, NULL);
> >  	if (ret)
> >  		goto out_put_object;
> >  
> > -	mutex_lock(&pfdev->shrinker_lock);
> >  	mutex_lock(&bo->mappings.lock);
> >  	if (args->madv == PANFROST_MADV_DONTNEED) {
> >  		struct panfrost_gem_mapping *first;
> > @@ -438,17 +440,8 @@ static int panfrost_ioctl_madvise(struct drm_device *dev, void *data,
> >  
> >  	args->retained = drm_gem_shmem_madvise_locked(&bo->base, args->madv);
> >  
> > -	if (args->retained) {
> > -		if (args->madv == PANFROST_MADV_DONTNEED)
> > -			list_move_tail(&bo->base.madv_list,
> > -				       &pfdev->shrinker_list);
> > -		else if (args->madv == PANFROST_MADV_WILLNEED)
> > -			list_del_init(&bo->base.madv_list);
> > -	}
> > -
> >  out_unlock_mappings:
> >  	mutex_unlock(&bo->mappings.lock);
> > -	mutex_unlock(&pfdev->shrinker_lock);
> >  	dma_resv_unlock(bo->base.base.resv);
> >  out_put_object:
> >  	drm_gem_object_put(gem_obj);
> > @@ -577,9 +570,6 @@ static int panfrost_probe(struct platform_device *pdev)
> >  	ddev->dev_private = pfdev;
> >  	pfdev->ddev = ddev;
> >  
> > -	mutex_init(&pfdev->shrinker_lock);
> > -	INIT_LIST_HEAD(&pfdev->shrinker_list);
> > -
> >  	err = panfrost_device_init(pfdev);
> >  	if (err) {
> >  		if (err != -EPROBE_DEFER)
> > @@ -601,10 +591,14 @@ static int panfrost_probe(struct platform_device *pdev)
> >  	if (err < 0)
> >  		goto err_out1;
> >  
> > -	panfrost_gem_shrinker_init(ddev);
> > +	err = drmm_gem_shmem_init(ddev);
> > +	if (err < 0)
> > +		goto err_out2;
> >  
> >  	return 0;
> >  
> > +err_out2:
> > +	drm_dev_unregister(ddev);
> >  err_out1:
> >  	pm_runtime_disable(pfdev->dev);
> >  	panfrost_device_fini(pfdev);
> > @@ -620,7 +614,6 @@ static void panfrost_remove(struct platform_device *pdev)
> >  	struct drm_device *ddev = pfdev->ddev;
> >  
> >  	drm_dev_unregister(ddev);
> > -	panfrost_gem_shrinker_cleanup(ddev);
> >  
> >  	pm_runtime_get_sync(pfdev->dev);
> >  	pm_runtime_disable(pfdev->dev);
> > diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
> > index 59c8c73c6a59..00165fca7f3d 100644
> > --- a/drivers/gpu/drm/panfrost/panfrost_gem.c
> > +++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
> > @@ -19,16 +19,6 @@ static void panfrost_gem_free_object(struct drm_gem_object *obj)
> >  	struct panfrost_gem_object *bo = to_panfrost_bo(obj);
> >  	struct panfrost_device *pfdev = obj->dev->dev_private;
> >  
> > -	/*
> > -	 * Make sure the BO is no longer inserted in the shrinker list before
> > -	 * taking care of the destruction itself. If we don't do that we have a
> > -	 * race condition between this function and what's done in
> > -	 * panfrost_gem_shrinker_scan().
> > -	 */
> > -	mutex_lock(&pfdev->shrinker_lock);
> > -	list_del_init(&bo->base.madv_list);
> > -	mutex_unlock(&pfdev->shrinker_lock);
> > -
> >  	/*
> >  	 * If we still have mappings attached to the BO, there's a problem in
> >  	 * our refcounting.
> > @@ -195,6 +185,25 @@ static int panfrost_gem_pin(struct drm_gem_object *obj)
> >  	return drm_gem_shmem_object_pin(obj);
> >  }
> >  
> > +static int panfrost_shmem_evict(struct drm_gem_object *obj)
> > +{
> > +	struct panfrost_gem_object *bo = to_panfrost_bo(obj);
> > +
> > +	if (!drm_gem_shmem_is_purgeable(&bo->base))
> > +		return -EBUSY;
> > +
> > +	if (!mutex_trylock(&bo->mappings.lock))
> > +		return -EBUSY;
> > +
> > +	panfrost_gem_teardown_mappings_locked(bo);
> > +
> > +	drm_gem_shmem_purge_locked(&bo->base);
> > +
> > +	mutex_unlock(&bo->mappings.lock);
> > +
> > +	return 0;
> > +}
> > +
> >  static const struct drm_gem_object_funcs panfrost_gem_funcs = {
> >  	.free = panfrost_gem_free_object,
> >  	.open = panfrost_gem_open,
> > @@ -207,6 +216,7 @@ static const struct drm_gem_object_funcs panfrost_gem_funcs = {
> >  	.vunmap = drm_gem_shmem_object_vunmap_locked,
> >  	.mmap = drm_gem_shmem_object_mmap,
> >  	.vm_ops = &drm_gem_shmem_vm_ops,
> > +	.evict = panfrost_shmem_evict,
> >  };
> >  
> >  /**
> > diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.h b/drivers/gpu/drm/panfrost/panfrost_gem.h
> > index ad2877eeeccd..6ad1bcedb932 100644
> > --- a/drivers/gpu/drm/panfrost/panfrost_gem.h
> > +++ b/drivers/gpu/drm/panfrost/panfrost_gem.h
> > @@ -30,12 +30,6 @@ struct panfrost_gem_object {
> >  		struct mutex lock;
> >  	} mappings;
> >  
> > -	/*
> > -	 * Count the number of jobs referencing this BO so we don't let the
> > -	 * shrinker reclaim this object prematurely.
> > -	 */
> > -	atomic_t gpu_usecount;
> > -
> >  	bool noexec		:1;
> >  	bool is_heap		:1;
> >  };
> > @@ -81,7 +75,4 @@ panfrost_gem_mapping_get(struct panfrost_gem_object *bo,
> >  void panfrost_gem_mapping_put(struct panfrost_gem_mapping *mapping);
> >  void panfrost_gem_teardown_mappings_locked(struct panfrost_gem_object *bo);
> >  
> > -void panfrost_gem_shrinker_init(struct drm_device *dev);
> > -void panfrost_gem_shrinker_cleanup(struct drm_device *dev);
> > -
> >  #endif /* __PANFROST_GEM_H__ */
> > diff --git a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
> > deleted file mode 100644
> > index 1aa94fff7072..000000000000
> > --- a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
> > +++ /dev/null
> > @@ -1,129 +0,0 @@
> > -// SPDX-License-Identifier: GPL-2.0
> > -/* Copyright (C) 2019 Arm Ltd.
> > - *
> > - * Based on msm_gem_freedreno.c:
> > - * Copyright (C) 2016 Red Hat
> > - * Author: Rob Clark <robdclark@gmail.com>
> > - */
> > -
> > -#include <linux/list.h>
> > -
> > -#include <drm/drm_device.h>
> > -#include <drm/drm_gem_shmem_helper.h>
> > -
> > -#include "panfrost_device.h"
> > -#include "panfrost_gem.h"
> > -#include "panfrost_mmu.h"
> > -
> > -static bool panfrost_gem_shmem_is_purgeable(struct drm_gem_shmem_object *shmem)
> > -{
> > -	return (shmem->madv > 0) &&
> > -		!refcount_read(&shmem->pages_pin_count) && shmem->sgt &&
> > -		!shmem->base.dma_buf && !shmem->base.import_attach;
> > -}
> > -
> > -static unsigned long
> > -panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
> > -{
> > -	struct panfrost_device *pfdev =
> > -		container_of(shrinker, struct panfrost_device, shrinker);
> > -	struct drm_gem_shmem_object *shmem;
> > -	unsigned long count = 0;
> > -
> > -	if (!mutex_trylock(&pfdev->shrinker_lock))
> > -		return 0;
> > -
> > -	list_for_each_entry(shmem, &pfdev->shrinker_list, madv_list) {
> > -		if (panfrost_gem_shmem_is_purgeable(shmem))
> > -			count += shmem->base.size >> PAGE_SHIFT;
> > -	}
> > -
> > -	mutex_unlock(&pfdev->shrinker_lock);
> > -
> > -	return count;
> > -}
> > -
> > -static bool panfrost_gem_purge(struct drm_gem_object *obj)
> > -{
> > -	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> > -	struct panfrost_gem_object *bo = to_panfrost_bo(obj);
> > -	bool ret = false;
> > -
> > -	if (atomic_read(&bo->gpu_usecount))
> > -		return false;
> > -
> > -	if (!mutex_trylock(&bo->mappings.lock))
> > -		return false;
> > -
> > -	if (!dma_resv_trylock(shmem->base.resv))
> > -		goto unlock_mappings;
> > -
> > -	panfrost_gem_teardown_mappings_locked(bo);
> > -	drm_gem_shmem_purge_locked(&bo->base);
> > -	ret = true;
> > -
> > -	dma_resv_unlock(shmem->base.resv);
> > -
> > -unlock_mappings:
> > -	mutex_unlock(&bo->mappings.lock);
> > -	return ret;
> > -}
> > -
> > -static unsigned long
> > -panfrost_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
> > -{
> > -	struct panfrost_device *pfdev =
> > -		container_of(shrinker, struct panfrost_device, shrinker);
> > -	struct drm_gem_shmem_object *shmem, *tmp;
> > -	unsigned long freed = 0;
> > -
> > -	if (!mutex_trylock(&pfdev->shrinker_lock))
> > -		return SHRINK_STOP;
> > -
> > -	list_for_each_entry_safe(shmem, tmp, &pfdev->shrinker_list, madv_list) {
> > -		if (freed >= sc->nr_to_scan)
> > -			break;
> > -		if (drm_gem_shmem_is_purgeable(shmem) &&
> > -		    panfrost_gem_purge(&shmem->base)) {
> > -			freed += shmem->base.size >> PAGE_SHIFT;
> > -			list_del_init(&shmem->madv_list);
> > -		}
> > -	}
> > -
> > -	mutex_unlock(&pfdev->shrinker_lock);
> > -
> > -	if (freed > 0)
> > -		pr_info_ratelimited("Purging %lu bytes\n", freed << PAGE_SHIFT);
> > -
> > -	return freed;
> > -}
> > -
> > -/**
> > - * panfrost_gem_shrinker_init - Initialize panfrost shrinker
> > - * @dev: DRM device
> > - *
> > - * This function registers and sets up the panfrost shrinker.
> > - */
> > -void panfrost_gem_shrinker_init(struct drm_device *dev)
> > -{
> > -	struct panfrost_device *pfdev = dev->dev_private;
> > -	pfdev->shrinker.count_objects = panfrost_gem_shrinker_count;
> > -	pfdev->shrinker.scan_objects = panfrost_gem_shrinker_scan;
> > -	pfdev->shrinker.seeks = DEFAULT_SEEKS;
> > -	WARN_ON(register_shrinker(&pfdev->shrinker, "drm-panfrost"));
> > -}
> > -
> > -/**
> > - * panfrost_gem_shrinker_cleanup - Clean up panfrost shrinker
> > - * @dev: DRM device
> > - *
> > - * This function unregisters the panfrost shrinker.
> > - */
> > -void panfrost_gem_shrinker_cleanup(struct drm_device *dev)
> > -{
> > -	struct panfrost_device *pfdev = dev->dev_private;
> > -
> > -	if (pfdev->shrinker.nr_deferred) {
> > -		unregister_shrinker(&pfdev->shrinker);
> > -	}
> > -}
> > diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
> > index a8b4827dc425..755128eb6c45 100644
> > --- a/drivers/gpu/drm/panfrost/panfrost_job.c
> > +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
> > @@ -272,6 +272,19 @@ static void panfrost_attach_object_fences(struct drm_gem_object **bos,
> >  		dma_resv_add_fence(bos[i]->resv, fence, DMA_RESV_USAGE_WRITE);
> >  }
> >  
> > +static int panfrost_objects_prepare(struct drm_gem_object **bos, int bo_count)
> > +{
> > +	struct panfrost_gem_object *bo;
> > +	int ret = 0;
> > +
> > +	while (!ret && bo_count--) {
> > +		bo = to_panfrost_bo(bos[bo_count]);
> > +		ret = bo->base.madv ? -ENOMEM : 0;
> > +	}
> > +
> > +	return ret;
> > +}
> > +
> >  int panfrost_job_push(struct panfrost_job *job)
> >  {
> >  	struct panfrost_device *pfdev = job->pfdev;
> > @@ -283,6 +296,10 @@ int panfrost_job_push(struct panfrost_job *job)
> >  	if (ret)
> >  		return ret;
> >  
> > +	ret = panfrost_objects_prepare(job->bos, job->bo_count);
> > +	if (ret)
> > +		goto unlock;
> > +
> >  	mutex_lock(&pfdev->sched_lock);
> >  	drm_sched_job_arm(&job->base);
> >  
> > @@ -324,7 +341,6 @@ static void panfrost_job_cleanup(struct kref *ref)
> >  			if (!job->mappings[i])
> >  				break;
> >  
> > -			atomic_dec(&job->mappings[i]->obj->gpu_usecount);
> >  			panfrost_gem_mapping_put(job->mappings[i]);
> >  		}
> >  		kvfree(job->mappings);
> > diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
> > index 2d7debc23ac1..13fe34236a0b 100644
> > --- a/include/drm/drm_gem_shmem_helper.h
> > +++ b/include/drm/drm_gem_shmem_helper.h
> > @@ -60,13 +60,6 @@ struct drm_gem_shmem_object {
> >  	 */
> >  	int madv;
> >  
> > -	/**
> > -	 * @madv_list: List entry for madvise tracking
> > -	 *
> > -	 * Typically used by drivers to track purgeable objects
> > -	 */
> > -	struct list_head madv_list;
> > -
> >  	/**
> >  	 * @sgt: Scatter/gather table for imported PRIME buffers
> >  	 */  
> 

Re: [PATCH v16 20/20] drm/panfrost: Switch to generic memory shrinker

[Steven Price]

On 05/09/2023 09:08, Boris Brezillon wrote:
> On Mon, 4 Sep 2023 14:20:24 +0100
> Steven Price <steven.price@arm.com> wrote:
> 
>> On 03/09/2023 18:07, Dmitry Osipenko wrote:
>>> Replace Panfrost's custom memory shrinker with a common drm-shmem
>>> memory shrinker.
>>>
>>> Tested-by: Steven Price <steven.price@arm.com> # Firefly-RK3288  
>>
>> I just gave this version of the series a spin and I can trigger the following 
>> warning:
>>
>> [  477.776163] ------------[ cut here ]------------
>> [  477.781353] WARNING: CPU: 0 PID: 292 at drivers/gpu/drm/drm_gem_shmem_helper.c:227 drm_gem_shmem_free+0x1fc/0x200 [drm_shmem_helper]
>> [  477.794790] panfrost ffa30000.gpu: drm_WARN_ON(refcount_read(&shmem->pages_use_count))
>> [  477.794797] Modules linked in: panfrost gpu_sched drm_shmem_helper
>> [  477.810942] CPU: 0 PID: 292 Comm: glmark2-es2-drm Not tainted 6.5.0-rc2-00527-gc8a0c16fa830 #1
>> [  477.820564] Hardware name: Rockchip (Device Tree)
>> [  477.825820]  unwind_backtrace from show_stack+0x10/0x14
>> [  477.831670]  show_stack from dump_stack_lvl+0x58/0x70
>> [  477.837319]  dump_stack_lvl from __warn+0x7c/0x1a4
>> [  477.842680]  __warn from warn_slowpath_fmt+0x134/0x1a0
>> [  477.848429]  warn_slowpath_fmt from drm_gem_shmem_free+0x1fc/0x200 [drm_shmem_helper]
>> [  477.857199]  drm_gem_shmem_free [drm_shmem_helper] from drm_gem_handle_delete+0x84/0xb0
>> [  477.866163]  drm_gem_handle_delete from drm_ioctl+0x214/0x4ec
>> [  477.872592]  drm_ioctl from sys_ioctl+0x568/0xd48
>> [  477.877857]  sys_ioctl from ret_fast_syscall+0x0/0x1c
>> [  477.883504] Exception stack(0xf0a49fa8 to 0xf0a49ff0)
>> [  477.889148] 9fa0:                   005969c0 bef34880 00000006 40086409 bef34880 00000001
>> [  477.898289] 9fc0: 005969c0 bef34880 40086409 00000036 bef34880 00590b64 00590aec 00000000
>> [  477.907428] 9fe0: b6ec408c bef3485c b6ead42f b6c31f98
>> [  477.913188] irq event stamp: 37296889
>> [  477.917319] hardirqs last  enabled at (37296951): [<c03c1968>] __up_console_sem+0x50/0x60
>> [  477.926531] hardirqs last disabled at (37296972): [<c03c1954>] __up_console_sem+0x3c/0x60
>> [  477.935714] softirqs last  enabled at (37296986): [<c03016cc>] __do_softirq+0x318/0x4d4
>> [  477.944708] softirqs last disabled at (37296981): [<c034f9ec>] __irq_exit_rcu+0x140/0x160
>> [  477.953878] ---[ end trace 0000000000000000 ]---
>>
>> So something, somewhere has gone wrong with the reference counts.
> 
> Missing `got_pages_sgt = true;` in the fault handler, when creating the
> sgt and populating the first 2MB chunk, I guess (should have been part
> of "drm/shmem-helper: Use flag for tracking page count bumped by
> get_pages_sgt()"). This kinda proves my point though: adding flags
> for things that can be inferred from other fields is a bad idea, because
> there's always the risk of not updating all the places that are manually
> filling these other fields...

Yes that seems to fix the problem. And I agree derived fields like this
are often problematic - it's better to avoid them whenever possible.

Steve