Re: [PATCH v6] drm/xe/dgfx: Release mmap mappings on rpm suspend

["Nilawar, Badal" <badal.nilawar@intel.com>]

Hi Matt,

Thanks for RB. Fixed v5 review comments. CI looks good for this patch so 
will proceed with merging.
Tests related to 
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/999 are passing 
with this patch. So as you suggested I will add Closes: 
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/999 while merging.

Thomas, Thanks for Ack.

Regards,
Badal

On 04-01-2024 18:37, Badal Nilawar wrote:
> Release all mmap mappings for all vram objects which are associated
> with userfault such that, while pcie function in D3hot, any access
> to memory mappings will raise a userfault.
> 
> Upon userfault, in order to access memory mappings, if graphics
> function is in D3 then runtime resume of dgpu will be triggered to
> transition to D0.
> 
> v2:
>    - Avoid iomem check before bo migration check as bo can migrate
>      to system memory (Matthew Auld)
> v3:
>    - Delete bo userfault link during bo destroy
>    - Upon bo move (vram-smem), do bo userfault link deletion in
>      xe_bo_move_notify instead of xe_bo_move (Thomas Hellström)
>    - Grab lock in rpm hook while deleting bo userfault link (Matthew Auld)
> v4:
>    - Add kernel doc and wrap vram_userfault related
>      stuff in the structure (Matthew Auld)
>    - Get rpm wakeref before taking dma reserve lock (Matthew Auld)
>    - In suspend path apply lock for entire list op
>      including list iteration (Matthew Auld)
> v5:
>    - Use mutex lock instead of spin lock
> v6:
>    - Fix review comments (Matthew Auld)
> 
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Matthew Auld <matthew.auld@intel.com>
> Cc: Anshuman Gupta <anshuman.gupta@intel.com>
> Signed-off-by: Badal Nilawar <badal.nilawar@intel.com>
> Acked-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> #For the xe_bo_move_notify() changes
> Reviewed-by: Matthew Auld <matthew.auld@intel.com>
> ---
>   drivers/gpu/drm/xe/xe_bo.c           | 56 ++++++++++++++++++++++++++--
>   drivers/gpu/drm/xe/xe_bo.h           |  2 +
>   drivers/gpu/drm/xe/xe_bo_types.h     |  3 ++
>   drivers/gpu/drm/xe/xe_device_types.h | 16 ++++++++
>   drivers/gpu/drm/xe/xe_pci.c          |  2 +
>   drivers/gpu/drm/xe/xe_pm.c           | 17 +++++++++
>   drivers/gpu/drm/xe/xe_pm.h           |  1 +
>   7 files changed, 93 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
> index 8e4a3b1f6b93..2e4d2157179c 100644
> --- a/drivers/gpu/drm/xe/xe_bo.c
> +++ b/drivers/gpu/drm/xe/xe_bo.c
> @@ -586,6 +586,8 @@ static int xe_bo_move_notify(struct xe_bo *bo,
>   {
>   	struct ttm_buffer_object *ttm_bo = &bo->ttm;
>   	struct xe_device *xe = ttm_to_xe_device(ttm_bo->bdev);
> +	struct ttm_resource *old_mem = ttm_bo->resource;
> +	u32 old_mem_type = old_mem ? old_mem->mem_type : XE_PL_SYSTEM;
>   	int ret;
>   
>   	/*
> @@ -605,6 +607,18 @@ static int xe_bo_move_notify(struct xe_bo *bo,
>   	if (ttm_bo->base.dma_buf && !ttm_bo->base.import_attach)
>   		dma_buf_move_notify(ttm_bo->base.dma_buf);
>   
> +	/*
> +	 * TTM has already nuked the mmap for us (see ttm_bo_unmap_virtual),
> +	 * so if we moved from VRAM make sure to unlink this from the userfault
> +	 * tracking.
> +	 */
> +	if (mem_type_is_vram(old_mem_type)) {
> +		mutex_lock(&xe->mem_access.vram_userfault.lock);
> +		if (!list_empty(&bo->vram_userfault_link))
> +			list_del_init(&bo->vram_userfault_link);
> +		mutex_unlock(&xe->mem_access.vram_userfault.lock);
> +	}
> +
>   	return 0;
>   }
>   
> @@ -1063,6 +1077,11 @@ static void xe_ttm_bo_destroy(struct ttm_buffer_object *ttm_bo)
>   	if (bo->vm && xe_bo_is_user(bo))
>   		xe_vm_put(bo->vm);
>   
> +	mutex_lock(&xe->mem_access.vram_userfault.lock);
> +	if (!list_empty(&bo->vram_userfault_link))
> +		list_del(&bo->vram_userfault_link);
> +	mutex_unlock(&xe->mem_access.vram_userfault.lock);
> +
>   	kfree(bo);
>   }
>   
> @@ -1110,16 +1129,20 @@ static vm_fault_t xe_gem_fault(struct vm_fault *vmf)
>   {
>   	struct ttm_buffer_object *tbo = vmf->vma->vm_private_data;
>   	struct drm_device *ddev = tbo->base.dev;
> +	struct xe_device *xe = to_xe_device(ddev);
> +	struct xe_bo *bo = ttm_to_xe_bo(tbo);
> +	bool needs_rpm = bo->flags & XE_BO_CREATE_VRAM_MASK;
>   	vm_fault_t ret;
>   	int idx, r = 0;
>   
> +	if (needs_rpm)
> +		xe_device_mem_access_get(xe);
> +
>   	ret = ttm_bo_vm_reserve(tbo, vmf);
>   	if (ret)
> -		return ret;
> +		goto out;
>   
>   	if (drm_dev_enter(ddev, &idx)) {
> -		struct xe_bo *bo = ttm_to_xe_bo(tbo);
> -
>   		trace_xe_bo_cpu_fault(bo);
>   
>   		if (should_migrate_to_system(bo)) {
> @@ -1137,10 +1160,24 @@ static vm_fault_t xe_gem_fault(struct vm_fault *vmf)
>   	} else {
>   		ret = ttm_bo_vm_dummy_page(vmf, vmf->vma->vm_page_prot);
>   	}
> +
>   	if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
> -		return ret;
> +		goto out;
> +	/*
> +	 * ttm_bo_vm_reserve() already has dma_resv_lock.
> +	 */
> +	if (ret == VM_FAULT_NOPAGE && mem_type_is_vram(tbo->resource->mem_type)) {
> +		mutex_lock(&xe->mem_access.vram_userfault.lock);
> +		if (list_empty(&bo->vram_userfault_link))
> +			list_add(&bo->vram_userfault_link, &xe->mem_access.vram_userfault.list);
> +		mutex_unlock(&xe->mem_access.vram_userfault.lock);
> +	}
>   
>   	dma_resv_unlock(tbo->base.resv);
> +out:
> +	if (needs_rpm)
> +		xe_device_mem_access_put(xe);
> +
>   	return ret;
>   }
>   
> @@ -1254,6 +1291,7 @@ struct xe_bo *___xe_bo_create_locked(struct xe_device *xe, struct xe_bo *bo,
>   #ifdef CONFIG_PROC_FS
>   	INIT_LIST_HEAD(&bo->client_link);
>   #endif
> +	INIT_LIST_HEAD(&bo->vram_userfault_link);
>   
>   	drm_gem_private_object_init(&xe->drm, &bo->ttm.base, size);
>   
> @@ -2264,6 +2302,16 @@ int xe_bo_dumb_create(struct drm_file *file_priv,
>   	return err;
>   }
>   
> +void xe_bo_runtime_pm_release_mmap_offset(struct xe_bo *bo)
> +{
> +	struct ttm_buffer_object *tbo = &bo->ttm;
> +	struct ttm_device *bdev = tbo->bdev;
> +
> +	drm_vma_node_unmap(&tbo->base.vma_node, bdev->dev_mapping);
> +
> +	list_del_init(&bo->vram_userfault_link);
> +}
> +
>   #if IS_ENABLED(CONFIG_DRM_XE_KUNIT_TEST)
>   #include "tests/xe_bo.c"
>   #endif
> diff --git a/drivers/gpu/drm/xe/xe_bo.h b/drivers/gpu/drm/xe/xe_bo.h
> index 97b32528c600..350cc73cadf8 100644
> --- a/drivers/gpu/drm/xe/xe_bo.h
> +++ b/drivers/gpu/drm/xe/xe_bo.h
> @@ -249,6 +249,8 @@ int xe_gem_create_ioctl(struct drm_device *dev, void *data,
>   			struct drm_file *file);
>   int xe_gem_mmap_offset_ioctl(struct drm_device *dev, void *data,
>   			     struct drm_file *file);
> +void xe_bo_runtime_pm_release_mmap_offset(struct xe_bo *bo);
> +
>   int xe_bo_dumb_create(struct drm_file *file_priv,
>   		      struct drm_device *dev,
>   		      struct drm_mode_create_dumb *args);
> diff --git a/drivers/gpu/drm/xe/xe_bo_types.h b/drivers/gpu/drm/xe/xe_bo_types.h
> index 64c2249a4e40..14ef13b7b421 100644
> --- a/drivers/gpu/drm/xe/xe_bo_types.h
> +++ b/drivers/gpu/drm/xe/xe_bo_types.h
> @@ -88,6 +88,9 @@ struct xe_bo {
>   	 * objects.
>   	 */
>   	u16 cpu_caching;
> +
> +	/** @vram_userfault_link: Link into @mem_access.vram_userfault.list */
> +		struct list_head vram_userfault_link;
>   };
>   
>   #define intel_bo_to_drm_bo(bo) (&(bo)->ttm.base)
> diff --git a/drivers/gpu/drm/xe/xe_device_types.h b/drivers/gpu/drm/xe/xe_device_types.h
> index 71f23ac365e6..dd0f4fb57683 100644
> --- a/drivers/gpu/drm/xe/xe_device_types.h
> +++ b/drivers/gpu/drm/xe/xe_device_types.h
> @@ -385,6 +385,22 @@ struct xe_device {
>   	struct {
>   		/** @ref: ref count of memory accesses */
>   		atomic_t ref;
> +
> +		/** @vram_userfault: Encapsulate vram_userfault related stuff */
> +		struct {
> +			/**
> +			 * @lock: Protects access to @vram_usefault.list
> +			 * Using mutex instead of spinlock as lock is applied to entire
> +			 * list operation which may sleep
> +			 */
> +			struct mutex lock;
> +
> +			/**
> +			 * @list: Keep list of userfaulted vram bo, which require to release their
> +			 * mmap mappings at runtime suspend path
> +			 */
> +			struct list_head list;
> +		} vram_userfault;
>   	} mem_access;
>   
>   	/**
> diff --git a/drivers/gpu/drm/xe/xe_pci.c b/drivers/gpu/drm/xe/xe_pci.c
> index 1f997353a78f..4de79a7c5dc2 100644
> --- a/drivers/gpu/drm/xe/xe_pci.c
> +++ b/drivers/gpu/drm/xe/xe_pci.c
> @@ -775,6 +775,8 @@ static int xe_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>   		str_yes_no(xe_device_has_sriov(xe)),
>   		xe_sriov_mode_to_string(xe_device_sriov_mode(xe)));
>   
> +	xe_pm_init_early(xe);
> +
>   	err = xe_device_probe(xe);
>   	if (err)
>   		return err;
> diff --git a/drivers/gpu/drm/xe/xe_pm.c b/drivers/gpu/drm/xe/xe_pm.c
> index b429c2876a76..d5f219796d7e 100644
> --- a/drivers/gpu/drm/xe/xe_pm.c
> +++ b/drivers/gpu/drm/xe/xe_pm.c
> @@ -163,6 +163,12 @@ static void xe_pm_runtime_init(struct xe_device *xe)
>   	pm_runtime_put(dev);
>   }
>   
> +void xe_pm_init_early(struct xe_device *xe)
> +{
> +	INIT_LIST_HEAD(&xe->mem_access.vram_userfault.list);
> +	drmm_mutex_init(&xe->drm, &xe->mem_access.vram_userfault.lock);
> +}
> +
>   void xe_pm_init(struct xe_device *xe)
>   {
>   	struct pci_dev *pdev = to_pci_dev(xe->drm.dev);
> @@ -214,6 +220,7 @@ struct task_struct *xe_pm_read_callback_task(struct xe_device *xe)
>   
>   int xe_pm_runtime_suspend(struct xe_device *xe)
>   {
> +	struct xe_bo *bo, *on;
>   	struct xe_gt *gt;
>   	u8 id;
>   	int err = 0;
> @@ -247,6 +254,16 @@ int xe_pm_runtime_suspend(struct xe_device *xe)
>   	 */
>   	lock_map_acquire(&xe_device_mem_access_lockdep_map);
>   
> +	/*
> +	 * Applying lock for entire list op as xe_ttm_bo_destroy and xe_bo_move_notify
> +	 * also checks and delets bo entry from user fault list.
> +	 */
> +	mutex_lock(&xe->mem_access.vram_userfault.lock);
> +	list_for_each_entry_safe(bo, on,
> +				 &xe->mem_access.vram_userfault.list, vram_userfault_link)
> +		xe_bo_runtime_pm_release_mmap_offset(bo);
> +	mutex_unlock(&xe->mem_access.vram_userfault.lock);
> +
>   	if (xe->d3cold.allowed) {
>   		err = xe_bo_evict_all(xe);
>   		if (err)
> diff --git a/drivers/gpu/drm/xe/xe_pm.h b/drivers/gpu/drm/xe/xe_pm.h
> index 6b9031f7af24..64a97c6726a7 100644
> --- a/drivers/gpu/drm/xe/xe_pm.h
> +++ b/drivers/gpu/drm/xe/xe_pm.h
> @@ -20,6 +20,7 @@ struct xe_device;
>   int xe_pm_suspend(struct xe_device *xe);
>   int xe_pm_resume(struct xe_device *xe);
>   
> +void xe_pm_init_early(struct xe_device *xe);
>   void xe_pm_init(struct xe_device *xe);
>   void xe_pm_runtime_fini(struct xe_device *xe);
>   int xe_pm_runtime_suspend(struct xe_device *xe);