[PATCH v3 00/33] drm/msm: sparse / "VM_BIND" support

[PATCH v3 00/33] drm/msm: sparse / "VM_BIND" support

[Rob Clark]

From: Rob Clark <robdclark@chromium.org>

Conversion to DRM GPU VA Manager[1], and adding support for Vulkan Sparse
Memory[2] in the form of:

1. A new VM_BIND submitqueue type for executing VM MSM_SUBMIT_BO_OP_MAP/
   MAP_NULL/UNMAP commands

2. A new VM_BIND ioctl to allow submitting batches of one or more
   MAP/MAP_NULL/UNMAP commands to a VM_BIND submitqueue

I did not implement support for synchronous VM_BIND commands.  Since
userspace could just immediately wait for the `SUBMIT` to complete, I don't
think we need this extra complexity in the kernel.  Synchronous/immediate
VM_BIND operations could be implemented with a 2nd VM_BIND submitqueue.

The corresponding mesa MR: https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32533

Changes in v3:
- Switched to seperate VM_BIND ioctl.  This makes the UABI a bit
  cleaner, but OTOH the userspace code was cleaner when the end result
  of either type of VkQueue lead to the same ioctl.  So I'm a bit on
  the fence.
- Switched to doing the gpuvm bookkeeping synchronously, and only
  deferring the pgtable updates.  This avoids needing to hold any resv
  locks in the fence signaling path, resolving the last shrinker related
  lockdep complaints.  OTOH it means userspace can trigger invalid
  pgtable updates with multiple VM_BIND queues.  In this case, we ensure
  that unmaps happen completely (to prevent userspace from using this to
  access free'd pages), mark the context as unusable, and move on with
  life.
- Link to v2: https://lore.kernel.org/all/20250319145425.51935-1-robdclark@gmail.com/

Changes in v2:
- Dropped Bibek Kumar Patro's arm-smmu patches[3], which have since been
  merged.
- Pre-allocate all the things, and drop HACK patch which disabled shrinker.
  This includes ensuring that vm_bo objects are allocated up front, pre-
  allocating VMA objects, and pre-allocating pages used for pgtable updates.
  The latter utilizes io_pgtable_cfg callbacks for pgtable alloc/free, that
  were initially added for panthor. 
- Add back support for BO dumping for devcoredump.
- Link to v1 (RFC): https://lore.kernel.org/dri-devel/20241207161651.410556-1-robdclark@gmail.com/T/#t

[1] https://www.kernel.org/doc/html/next/gpu/drm-mm.html#drm-gpuvm
[2] https://docs.vulkan.org/spec/latest/chapters/sparsemem.html
[3] https://patchwork.kernel.org/project/linux-arm-kernel/list/?series=909700

Rob Clark (33):
  drm/gpuvm: Don't require obj lock in destructor path
  drm/gpuvm: Allow VAs to hold soft reference to BOs
  iommu/io-pgtable-arm: Add quirk to quiet WARN_ON()
  drm/msm: Rename msm_file_private -> msm_context
  drm/msm: Improve msm_context comments
  drm/msm: Rename msm_gem_address_space -> msm_gem_vm
  drm/msm: Remove vram carveout support
  drm/msm: Collapse vma allocation and initialization
  drm/msm: Collapse vma close and delete
  drm/msm: Don't close VMAs on purge
  drm/msm: drm_gpuvm conversion
  drm/msm: Convert vm locking
  drm/msm: Use drm_gpuvm types more
  drm/msm: Split out helper to get iommu prot flags
  drm/msm: Add mmu support for non-zero offset
  drm/msm: Add PRR support
  drm/msm: Rename msm_gem_vma_purge() -> _unmap()
  drm/msm: Lazily create context VM
  drm/msm: Add opt-in for VM_BIND
  drm/msm: Mark VM as unusable on GPU hangs
  drm/msm: Add _NO_SHARE flag
  drm/msm: Crashdump prep for sparse mappings
  drm/msm: rd dumping prep for sparse mappings
  drm/msm: Crashdec support for sparse
  drm/msm: rd dumping support for sparse
  drm/msm: Extract out syncobj helpers
  drm/msm: Use DMA_RESV_USAGE_BOOKKEEP/KERNEL
  drm/msm: Add VM_BIND submitqueue
  drm/msm: Support IO_PGTABLE_QUIRK_NO_WARN_ON
  drm/msm: Support pgtable preallocation
  drm/msm: Split out map/unmap ops
  drm/msm: Add VM_BIND ioctl
  drm/msm: Bump UAPI version

 drivers/gpu/drm/drm_gpuvm.c                   |   15 +-
 drivers/gpu/drm/msm/Kconfig                   |    1 +
 drivers/gpu/drm/msm/Makefile                  |    1 +
 drivers/gpu/drm/msm/adreno/a2xx_gpu.c         |   25 +-
 drivers/gpu/drm/msm/adreno/a2xx_gpummu.c      |    5 +-
 drivers/gpu/drm/msm/adreno/a3xx_gpu.c         |   17 +-
 drivers/gpu/drm/msm/adreno/a4xx_gpu.c         |   17 +-
 drivers/gpu/drm/msm/adreno/a5xx_debugfs.c     |    4 +-
 drivers/gpu/drm/msm/adreno/a5xx_gpu.c         |   22 +-
 drivers/gpu/drm/msm/adreno/a5xx_power.c       |    2 +-
 drivers/gpu/drm/msm/adreno/a5xx_preempt.c     |   10 +-
 drivers/gpu/drm/msm/adreno/a6xx_gmu.c         |   32 +-
 drivers/gpu/drm/msm/adreno/a6xx_gmu.h         |    2 +-
 drivers/gpu/drm/msm/adreno/a6xx_gpu.c         |   49 +-
 drivers/gpu/drm/msm/adreno/a6xx_gpu_state.c   |    6 +-
 drivers/gpu/drm/msm/adreno/a6xx_preempt.c     |   10 +-
 drivers/gpu/drm/msm/adreno/adreno_device.c    |    4 -
 drivers/gpu/drm/msm/adreno/adreno_gpu.c       |   88 +-
 drivers/gpu/drm/msm/adreno/adreno_gpu.h       |   23 +-
 .../drm/msm/disp/dpu1/dpu_encoder_phys_wb.c   |   14 +-
 drivers/gpu/drm/msm/disp/dpu1/dpu_formats.c   |   18 +-
 drivers/gpu/drm/msm/disp/dpu1/dpu_formats.h   |    2 +-
 drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c       |   18 +-
 drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c     |   14 +-
 drivers/gpu/drm/msm/disp/dpu1/dpu_plane.h     |    4 +-
 drivers/gpu/drm/msm/disp/mdp4/mdp4_crtc.c     |    6 +-
 drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.c      |   28 +-
 drivers/gpu/drm/msm/disp/mdp4/mdp4_plane.c    |   12 +-
 drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c     |    4 +-
 drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c      |   19 +-
 drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c    |   12 +-
 drivers/gpu/drm/msm/dsi/dsi_host.c            |   14 +-
 drivers/gpu/drm/msm/msm_drv.c                 |  183 +--
 drivers/gpu/drm/msm/msm_drv.h                 |   35 +-
 drivers/gpu/drm/msm/msm_fb.c                  |   18 +-
 drivers/gpu/drm/msm/msm_fbdev.c               |    2 +-
 drivers/gpu/drm/msm/msm_gem.c                 |  489 +++----
 drivers/gpu/drm/msm/msm_gem.h                 |  217 ++-
 drivers/gpu/drm/msm/msm_gem_prime.c           |   15 +
 drivers/gpu/drm/msm/msm_gem_shrinker.c        |    4 +-
 drivers/gpu/drm/msm/msm_gem_submit.c          |  295 ++--
 drivers/gpu/drm/msm/msm_gem_vma.c             | 1265 +++++++++++++++--
 drivers/gpu/drm/msm/msm_gpu.c                 |  171 ++-
 drivers/gpu/drm/msm/msm_gpu.h                 |  132 +-
 drivers/gpu/drm/msm/msm_iommu.c               |  298 +++-
 drivers/gpu/drm/msm/msm_kms.c                 |   18 +-
 drivers/gpu/drm/msm/msm_kms.h                 |    2 +-
 drivers/gpu/drm/msm/msm_mmu.h                 |   38 +-
 drivers/gpu/drm/msm/msm_rd.c                  |   62 +-
 drivers/gpu/drm/msm/msm_ringbuffer.c          |    4 +-
 drivers/gpu/drm/msm/msm_submitqueue.c         |   86 +-
 drivers/gpu/drm/msm/msm_syncobj.c             |  172 +++
 drivers/gpu/drm/msm/msm_syncobj.h             |   37 +
 drivers/iommu/io-pgtable-arm.c                |   18 +-
 include/drm/drm_gpuvm.h                       |   12 +-
 include/linux/io-pgtable.h                    |    8 +
 include/uapi/drm/msm_drm.h                    |  149 +-
 57 files changed, 3012 insertions(+), 1216 deletions(-)
 create mode 100644 drivers/gpu/drm/msm/msm_syncobj.c
 create mode 100644 drivers/gpu/drm/msm/msm_syncobj.h

-- 
2.49.0

[PATCH v3 03/33] iommu/io-pgtable-arm: Add quirk to quiet WARN_ON()

[Rob Clark]

From: Rob Clark <robdclark@chromium.org>

In situations where mapping/unmapping squence can be controlled by
userspace, attempting to map over a region that has not yet been
unmapped is an error.  But not something that should spam dmesg.

Signed-off-by: Rob Clark <robdclark@chromium.org>
---
 drivers/iommu/io-pgtable-arm.c | 18 ++++++++++++------
 include/linux/io-pgtable.h     |  8 ++++++++
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index f27965caf6a1..99523505dac5 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -475,7 +475,7 @@ static int __arm_lpae_map(struct arm_lpae_io_pgtable *data, unsigned long iova,
 		cptep = iopte_deref(pte, data);
 	} else if (pte) {
 		/* We require an unmap first */
-		WARN_ON(!selftest_running);
+		WARN_ON(!selftest_running && !(cfg->quirks & IO_PGTABLE_QUIRK_NO_WARN_ON));
 		return -EEXIST;
 	}
 
@@ -649,8 +649,10 @@ static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data,
 	unmap_idx_start = ARM_LPAE_LVL_IDX(iova, lvl, data);
 	ptep += unmap_idx_start;
 	pte = READ_ONCE(*ptep);
-	if (WARN_ON(!pte))
-		return 0;
+	if (!pte) {
+		WARN_ON(!(data->iop.cfg.quirks & IO_PGTABLE_QUIRK_NO_WARN_ON));
+		return -ENOENT;
+	}
 
 	/* If the size matches this level, we're in the right place */
 	if (size == ARM_LPAE_BLOCK_SIZE(lvl, data)) {
@@ -660,8 +662,10 @@ static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data,
 		/* Find and handle non-leaf entries */
 		for (i = 0; i < num_entries; i++) {
 			pte = READ_ONCE(ptep[i]);
-			if (WARN_ON(!pte))
+			if (!pte) {
+				WARN_ON(!(data->iop.cfg.quirks & IO_PGTABLE_QUIRK_NO_WARN_ON));
 				break;
+			}
 
 			if (!iopte_leaf(pte, lvl, iop->fmt)) {
 				__arm_lpae_clear_pte(&ptep[i], &iop->cfg, 1);
@@ -976,7 +980,8 @@ arm_64_lpae_alloc_pgtable_s1(struct io_pgtable_cfg *cfg, void *cookie)
 	if (cfg->quirks & ~(IO_PGTABLE_QUIRK_ARM_NS |
 			    IO_PGTABLE_QUIRK_ARM_TTBR1 |
 			    IO_PGTABLE_QUIRK_ARM_OUTER_WBWA |
-			    IO_PGTABLE_QUIRK_ARM_HD))
+			    IO_PGTABLE_QUIRK_ARM_HD |
+			    IO_PGTABLE_QUIRK_NO_WARN_ON))
 		return NULL;
 
 	data = arm_lpae_alloc_pgtable(cfg);
@@ -1079,7 +1084,8 @@ arm_64_lpae_alloc_pgtable_s2(struct io_pgtable_cfg *cfg, void *cookie)
 	struct arm_lpae_io_pgtable *data;
 	typeof(&cfg->arm_lpae_s2_cfg.vtcr) vtcr = &cfg->arm_lpae_s2_cfg.vtcr;
 
-	if (cfg->quirks & ~(IO_PGTABLE_QUIRK_ARM_S2FWB))
+	if (cfg->quirks & ~(IO_PGTABLE_QUIRK_ARM_S2FWB |
+			    IO_PGTABLE_QUIRK_NO_WARN_ON))
 		return NULL;
 
 	data = arm_lpae_alloc_pgtable(cfg);
diff --git a/include/linux/io-pgtable.h b/include/linux/io-pgtable.h
index bba2a51c87d2..639b8f4fb87d 100644
--- a/include/linux/io-pgtable.h
+++ b/include/linux/io-pgtable.h
@@ -88,6 +88,13 @@ struct io_pgtable_cfg {
 	 *
 	 * IO_PGTABLE_QUIRK_ARM_HD: Enables dirty tracking in stage 1 pagetable.
 	 * IO_PGTABLE_QUIRK_ARM_S2FWB: Use the FWB format for the MemAttrs bits
+	 *
+	 * IO_PGTABLE_QUIRK_NO_WARN_ON: Do not WARN_ON() on conflicting
+	 *	mappings, but silently return -EEXISTS.  Normally an attempt
+	 *	to map over an existing mapping would indicate some sort of
+	 *	kernel bug, which would justify the WARN_ON().  But for GPU
+	 *	drivers, this could be under control of userspace.  Which
+	 *	deserves an error return, but not to spam dmesg.
 	 */
 	#define IO_PGTABLE_QUIRK_ARM_NS			BIT(0)
 	#define IO_PGTABLE_QUIRK_NO_PERMS		BIT(1)
@@ -97,6 +104,7 @@ struct io_pgtable_cfg {
 	#define IO_PGTABLE_QUIRK_ARM_OUTER_WBWA		BIT(6)
 	#define IO_PGTABLE_QUIRK_ARM_HD			BIT(7)
 	#define IO_PGTABLE_QUIRK_ARM_S2FWB		BIT(8)
+	#define IO_PGTABLE_QUIRK_NO_WARN_ON		BIT(9)
 	unsigned long			quirks;
 	unsigned long			pgsize_bitmap;
 	unsigned int			ias;
-- 
2.49.0

Re: [PATCH v3 03/33] iommu/io-pgtable-arm: Add quirk to quiet WARN_ON()

[Jason Gunthorpe]

On Mon, Apr 28, 2025 at 01:54:10PM -0700, Rob Clark wrote:
> From: Rob Clark <robdclark@chromium.org>
> 
> In situations where mapping/unmapping squence can be controlled by
> userspace, attempting to map over a region that has not yet been
> unmapped is an error.  But not something that should spam dmesg.

I think if you want to do something like that using the iommu API the
expectation is for the caller to do a iova_to_phys to check what is
mapped first? That seems kind of lame..

Maybe page table driver should not not be doing these WARNs at all. If
we want to check for that the core iommu code should have the WARN_ON?

eg iommufd already has a WARN_ON around iommu_unmap failures so having
one in the ARM page table is a double WARN.

Don't really like using a quirk to change the API contract.

Jason

Re: [PATCH v3 03/33] iommu/io-pgtable-arm: Add quirk to quiet WARN_ON()

[Rob Clark]

On Tue, Apr 29, 2025 at 5:28 AM Jason Gunthorpe <jgg@ziepe.ca> wrote:
>
> On Mon, Apr 28, 2025 at 01:54:10PM -0700, Rob Clark wrote:
> > From: Rob Clark <robdclark@chromium.org>
> >
> > In situations where mapping/unmapping squence can be controlled by
> > userspace, attempting to map over a region that has not yet been
> > unmapped is an error.  But not something that should spam dmesg.
>
> I think if you want to do something like that using the iommu API the
> expectation is for the caller to do a iova_to_phys to check what is
> mapped first? That seems kind of lame..
>
> Maybe page table driver should not not be doing these WARNs at all. If
> we want to check for that the core iommu code should have the WARN_ON?
>
> eg iommufd already has a WARN_ON around iommu_unmap failures so having
> one in the ARM page table is a double WARN.
>
> Don't really like using a quirk to change the API contract.

I'd also be ok to have the WARN_ON instead in the iommu code.  In the
case where this quirk is needed, I'm using the io_pgtable helpers
directly, not going via the iommu layer.

BR,
-R

Re: [PATCH v3 03/33] iommu/io-pgtable-arm: Add quirk to quiet WARN_ON()

[Jason Gunthorpe]

On Tue, Apr 29, 2025 at 06:58:32AM -0700, Rob Clark wrote:
> On Tue, Apr 29, 2025 at 5:28 AM Jason Gunthorpe <jgg@ziepe.ca> wrote:
> >
> > On Mon, Apr 28, 2025 at 01:54:10PM -0700, Rob Clark wrote:
> > > From: Rob Clark <robdclark@chromium.org>
> > >
> > > In situations where mapping/unmapping squence can be controlled by
> > > userspace, attempting to map over a region that has not yet been
> > > unmapped is an error.  But not something that should spam dmesg.
> >
> > I think if you want to do something like that using the iommu API the
> > expectation is for the caller to do a iova_to_phys to check what is
> > mapped first? That seems kind of lame..
> >
> > Maybe page table driver should not not be doing these WARNs at all. If
> > we want to check for that the core iommu code should have the WARN_ON?
> >
> > eg iommufd already has a WARN_ON around iommu_unmap failures so having
> > one in the ARM page table is a double WARN.
> >
> > Don't really like using a quirk to change the API contract.
> 
> I'd also be ok to have the WARN_ON instead in the iommu code.  In the
> case where this quirk is needed, I'm using the io_pgtable helpers
> directly, not going via the iommu layer.

Yes, that was my thought

Then all the iommu_map/unmap() calls behave consistently here..

Jason

Re: [PATCH v3 03/33] iommu/io-pgtable-arm: Add quirk to quiet WARN_ON()

[Robin Murphy]

On 28/04/2025 9:54 pm, Rob Clark wrote:
> From: Rob Clark <robdclark@chromium.org>
> 
> In situations where mapping/unmapping squence can be controlled by
> userspace, attempting to map over a region that has not yet been
> unmapped is an error.  But not something that should spam dmesg.
> 
> Signed-off-by: Rob Clark <robdclark@chromium.org>
> ---
>   drivers/iommu/io-pgtable-arm.c | 18 ++++++++++++------
>   include/linux/io-pgtable.h     |  8 ++++++++
>   2 files changed, 20 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
> index f27965caf6a1..99523505dac5 100644
> --- a/drivers/iommu/io-pgtable-arm.c
> +++ b/drivers/iommu/io-pgtable-arm.c
> @@ -475,7 +475,7 @@ static int __arm_lpae_map(struct arm_lpae_io_pgtable *data, unsigned long iova,
>   		cptep = iopte_deref(pte, data);
>   	} else if (pte) {
>   		/* We require an unmap first */
> -		WARN_ON(!selftest_running);
> +		WARN_ON(!selftest_running && !(cfg->quirks & IO_PGTABLE_QUIRK_NO_WARN_ON));

If we are going to have this as a general mechanism then the selftests 
should use it as well.

Thanks,
Robin.

>   		return -EEXIST;
>   	}
>   
> @@ -649,8 +649,10 @@ static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data,
>   	unmap_idx_start = ARM_LPAE_LVL_IDX(iova, lvl, data);
>   	ptep += unmap_idx_start;
>   	pte = READ_ONCE(*ptep);
> -	if (WARN_ON(!pte))
> -		return 0;
> +	if (!pte) {
> +		WARN_ON(!(data->iop.cfg.quirks & IO_PGTABLE_QUIRK_NO_WARN_ON));
> +		return -ENOENT;
> +	}
>   
>   	/* If the size matches this level, we're in the right place */
>   	if (size == ARM_LPAE_BLOCK_SIZE(lvl, data)) {
> @@ -660,8 +662,10 @@ static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data,
>   		/* Find and handle non-leaf entries */
>   		for (i = 0; i < num_entries; i++) {
>   			pte = READ_ONCE(ptep[i]);
> -			if (WARN_ON(!pte))
> +			if (!pte) {
> +				WARN_ON(!(data->iop.cfg.quirks & IO_PGTABLE_QUIRK_NO_WARN_ON));
>   				break;
> +			}
>   
>   			if (!iopte_leaf(pte, lvl, iop->fmt)) {
>   				__arm_lpae_clear_pte(&ptep[i], &iop->cfg, 1);
> @@ -976,7 +980,8 @@ arm_64_lpae_alloc_pgtable_s1(struct io_pgtable_cfg *cfg, void *cookie)
>   	if (cfg->quirks & ~(IO_PGTABLE_QUIRK_ARM_NS |
>   			    IO_PGTABLE_QUIRK_ARM_TTBR1 |
>   			    IO_PGTABLE_QUIRK_ARM_OUTER_WBWA |
> -			    IO_PGTABLE_QUIRK_ARM_HD))
> +			    IO_PGTABLE_QUIRK_ARM_HD |
> +			    IO_PGTABLE_QUIRK_NO_WARN_ON))
>   		return NULL;
>   
>   	data = arm_lpae_alloc_pgtable(cfg);
> @@ -1079,7 +1084,8 @@ arm_64_lpae_alloc_pgtable_s2(struct io_pgtable_cfg *cfg, void *cookie)
>   	struct arm_lpae_io_pgtable *data;
>   	typeof(&cfg->arm_lpae_s2_cfg.vtcr) vtcr = &cfg->arm_lpae_s2_cfg.vtcr;
>   
> -	if (cfg->quirks & ~(IO_PGTABLE_QUIRK_ARM_S2FWB))
> +	if (cfg->quirks & ~(IO_PGTABLE_QUIRK_ARM_S2FWB |
> +			    IO_PGTABLE_QUIRK_NO_WARN_ON))
>   		return NULL;
>   
>   	data = arm_lpae_alloc_pgtable(cfg);
> diff --git a/include/linux/io-pgtable.h b/include/linux/io-pgtable.h
> index bba2a51c87d2..639b8f4fb87d 100644
> --- a/include/linux/io-pgtable.h
> +++ b/include/linux/io-pgtable.h
> @@ -88,6 +88,13 @@ struct io_pgtable_cfg {
>   	 *
>   	 * IO_PGTABLE_QUIRK_ARM_HD: Enables dirty tracking in stage 1 pagetable.
>   	 * IO_PGTABLE_QUIRK_ARM_S2FWB: Use the FWB format for the MemAttrs bits
> +	 *
> +	 * IO_PGTABLE_QUIRK_NO_WARN_ON: Do not WARN_ON() on conflicting
> +	 *	mappings, but silently return -EEXISTS.  Normally an attempt
> +	 *	to map over an existing mapping would indicate some sort of
> +	 *	kernel bug, which would justify the WARN_ON().  But for GPU
> +	 *	drivers, this could be under control of userspace.  Which
> +	 *	deserves an error return, but not to spam dmesg.
>   	 */
>   	#define IO_PGTABLE_QUIRK_ARM_NS			BIT(0)
>   	#define IO_PGTABLE_QUIRK_NO_PERMS		BIT(1)
> @@ -97,6 +104,7 @@ struct io_pgtable_cfg {
>   	#define IO_PGTABLE_QUIRK_ARM_OUTER_WBWA		BIT(6)
>   	#define IO_PGTABLE_QUIRK_ARM_HD			BIT(7)
>   	#define IO_PGTABLE_QUIRK_ARM_S2FWB		BIT(8)
> +	#define IO_PGTABLE_QUIRK_NO_WARN_ON		BIT(9)
>   	unsigned long			quirks;
>   	unsigned long			pgsize_bitmap;
>   	unsigned int			ias;

Re: [PATCH v3 03/33] iommu/io-pgtable-arm: Add quirk to quiet WARN_ON()

[Rob Clark]

On Tue, Apr 29, 2025 at 5:38 AM Robin Murphy <robin.murphy@arm.com> wrote:
>
> On 28/04/2025 9:54 pm, Rob Clark wrote:
> > From: Rob Clark <robdclark@chromium.org>
> >
> > In situations where mapping/unmapping squence can be controlled by
> > userspace, attempting to map over a region that has not yet been
> > unmapped is an error.  But not something that should spam dmesg.
> >
> > Signed-off-by: Rob Clark <robdclark@chromium.org>
> > ---
> >   drivers/iommu/io-pgtable-arm.c | 18 ++++++++++++------
> >   include/linux/io-pgtable.h     |  8 ++++++++
> >   2 files changed, 20 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
> > index f27965caf6a1..99523505dac5 100644
> > --- a/drivers/iommu/io-pgtable-arm.c
> > +++ b/drivers/iommu/io-pgtable-arm.c
> > @@ -475,7 +475,7 @@ static int __arm_lpae_map(struct arm_lpae_io_pgtable *data, unsigned long iova,
> >               cptep = iopte_deref(pte, data);
> >       } else if (pte) {
> >               /* We require an unmap first */
> > -             WARN_ON(!selftest_running);
> > +             WARN_ON(!selftest_running && !(cfg->quirks & IO_PGTABLE_QUIRK_NO_WARN_ON));
>
> If we are going to have this as a general mechanism then the selftests
> should use it as well.

Makes sense, I can remove the selftest_running hack in the next version.

BR,
-R

> Thanks,
> Robin.
>
> >               return -EEXIST;
> >       }
> >
> > @@ -649,8 +649,10 @@ static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data,
> >       unmap_idx_start = ARM_LPAE_LVL_IDX(iova, lvl, data);
> >       ptep += unmap_idx_start;
> >       pte = READ_ONCE(*ptep);
> > -     if (WARN_ON(!pte))
> > -             return 0;
> > +     if (!pte) {
> > +             WARN_ON(!(data->iop.cfg.quirks & IO_PGTABLE_QUIRK_NO_WARN_ON));
> > +             return -ENOENT;
> > +     }
> >
> >       /* If the size matches this level, we're in the right place */
> >       if (size == ARM_LPAE_BLOCK_SIZE(lvl, data)) {
> > @@ -660,8 +662,10 @@ static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data,
> >               /* Find and handle non-leaf entries */
> >               for (i = 0; i < num_entries; i++) {
> >                       pte = READ_ONCE(ptep[i]);
> > -                     if (WARN_ON(!pte))
> > +                     if (!pte) {
> > +                             WARN_ON(!(data->iop.cfg.quirks & IO_PGTABLE_QUIRK_NO_WARN_ON));
> >                               break;
> > +                     }
> >
> >                       if (!iopte_leaf(pte, lvl, iop->fmt)) {
> >                               __arm_lpae_clear_pte(&ptep[i], &iop->cfg, 1);
> > @@ -976,7 +980,8 @@ arm_64_lpae_alloc_pgtable_s1(struct io_pgtable_cfg *cfg, void *cookie)
> >       if (cfg->quirks & ~(IO_PGTABLE_QUIRK_ARM_NS |
> >                           IO_PGTABLE_QUIRK_ARM_TTBR1 |
> >                           IO_PGTABLE_QUIRK_ARM_OUTER_WBWA |
> > -                         IO_PGTABLE_QUIRK_ARM_HD))
> > +                         IO_PGTABLE_QUIRK_ARM_HD |
> > +                         IO_PGTABLE_QUIRK_NO_WARN_ON))
> >               return NULL;
> >
> >       data = arm_lpae_alloc_pgtable(cfg);
> > @@ -1079,7 +1084,8 @@ arm_64_lpae_alloc_pgtable_s2(struct io_pgtable_cfg *cfg, void *cookie)
> >       struct arm_lpae_io_pgtable *data;
> >       typeof(&cfg->arm_lpae_s2_cfg.vtcr) vtcr = &cfg->arm_lpae_s2_cfg.vtcr;
> >
> > -     if (cfg->quirks & ~(IO_PGTABLE_QUIRK_ARM_S2FWB))
> > +     if (cfg->quirks & ~(IO_PGTABLE_QUIRK_ARM_S2FWB |
> > +                         IO_PGTABLE_QUIRK_NO_WARN_ON))
> >               return NULL;
> >
> >       data = arm_lpae_alloc_pgtable(cfg);
> > diff --git a/include/linux/io-pgtable.h b/include/linux/io-pgtable.h
> > index bba2a51c87d2..639b8f4fb87d 100644
> > --- a/include/linux/io-pgtable.h
> > +++ b/include/linux/io-pgtable.h
> > @@ -88,6 +88,13 @@ struct io_pgtable_cfg {
> >        *
> >        * IO_PGTABLE_QUIRK_ARM_HD: Enables dirty tracking in stage 1 pagetable.
> >        * IO_PGTABLE_QUIRK_ARM_S2FWB: Use the FWB format for the MemAttrs bits
> > +      *
> > +      * IO_PGTABLE_QUIRK_NO_WARN_ON: Do not WARN_ON() on conflicting
> > +      *      mappings, but silently return -EEXISTS.  Normally an attempt
> > +      *      to map over an existing mapping would indicate some sort of
> > +      *      kernel bug, which would justify the WARN_ON().  But for GPU
> > +      *      drivers, this could be under control of userspace.  Which
> > +      *      deserves an error return, but not to spam dmesg.
> >        */
> >       #define IO_PGTABLE_QUIRK_ARM_NS                 BIT(0)
> >       #define IO_PGTABLE_QUIRK_NO_PERMS               BIT(1)
> > @@ -97,6 +104,7 @@ struct io_pgtable_cfg {
> >       #define IO_PGTABLE_QUIRK_ARM_OUTER_WBWA         BIT(6)
> >       #define IO_PGTABLE_QUIRK_ARM_HD                 BIT(7)
> >       #define IO_PGTABLE_QUIRK_ARM_S2FWB              BIT(8)
> > +     #define IO_PGTABLE_QUIRK_NO_WARN_ON             BIT(9)
> >       unsigned long                   quirks;
> >       unsigned long                   pgsize_bitmap;
> >       unsigned int                    ias;