[PATCH v3] drm/xe/dgfx: Release mmap mappings on rpm suspend
Matthew Auld
matthew.auld at intel.com
Thu Dec 21 09:21:26 UTC 2023
On 20/12/2023 18:50, 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:
> - Add lock dep assertion before updating vram_userfault_count (Rodrigo)
> - 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)
>
> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> Cc: Matthew Auld <matthew.auld at intel.com>
> Cc: Anshuman Gupta <anshuman.gupta at intel.com>
> Signed-off-by: Badal Nilawar <badal.nilawar at intel.com>
> ---
> drivers/gpu/drm/xe/xe_bo.c | 65 +++++++++++++++++++++++++++-
> drivers/gpu/drm/xe/xe_bo.h | 2 +
> drivers/gpu/drm/xe/xe_bo_types.h | 5 +++
> drivers/gpu/drm/xe/xe_device_types.h | 20 +++++++++
> drivers/gpu/drm/xe/xe_pm.c | 7 +++
> 5 files changed, 98 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
> index 8e4a3b1f6b93..2ab933f50192 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;
>
> /*
> @@ -597,6 +599,7 @@ static int xe_bo_move_notify(struct xe_bo *bo,
> return -EINVAL;
>
> xe_bo_vunmap(bo);
> +
> ret = xe_bo_trigger_rebind(xe, bo, ctx);
> if (ret)
> return ret;
> @@ -605,6 +608,18 @@ 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)) {
> + spin_lock(&xe->mem_access.vram_userfault_lock);
> + if (!list_empty(&bo->vram_userfault_link))
> + list_del_init(&bo->vram_userfault_link);
> + spin_unlock(&xe->mem_access.vram_userfault_lock);
> + }
> +
> return 0;
> }
>
> @@ -1063,6 +1078,11 @@ 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);
>
> + spin_lock(&xe->mem_access.vram_userfault_lock);
> + if (!list_empty(&bo->vram_userfault_link))
> + list_del(&bo->vram_userfault_link);
> + spin_unlock(&xe->mem_access.vram_userfault_lock);
> +
> kfree(bo);
> }
>
> @@ -1110,6 +1130,8 @@ 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_bo *bo = NULL;
> + struct xe_device *xe = to_xe_device(ddev);
> vm_fault_t ret;
> int idx, r = 0;
>
> @@ -1118,7 +1140,7 @@ static vm_fault_t xe_gem_fault(struct vm_fault *vmf)
> return ret;
>
> if (drm_dev_enter(ddev, &idx)) {
> - struct xe_bo *bo = ttm_to_xe_bo(tbo);
> + bo = ttm_to_xe_bo(tbo);
>
> trace_xe_bo_cpu_fault(bo);
>
> @@ -1137,10 +1159,31 @@ 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;
> + /*
> + * ttm_bo_vm_reserve() already has dma_resv_lock.
> + * vram_userfault_count is protected by dma_resv lock and rpm wakeref.
> + */
> + if (ret == VM_FAULT_NOPAGE && bo && !bo->vram_userfault_count) {
> + if (tbo->resource->bus.is_iomem) {
> + dma_resv_assert_held(tbo->base.resv);
> +
> + xe_device_mem_access_get(xe);
Thinking ahead for d3cold, we probably don't want to introduce more
places that do dma-resv -> access_get. Not a big deal for now, but at
some point someone will have to fix this. Please consider if we can
easily move this higher up now.
> +
> + bo->vram_userfault_count = 1;
> +
> + spin_lock(&xe->mem_access.vram_userfault_lock);
> + list_add(&bo->vram_userfault_link, &xe->mem_access.vram_userfault_list);
> + spin_unlock(&xe->mem_access.vram_userfault_lock);
> +
> + xe_device_mem_access_put(xe);
> + }
> + }
>
> dma_resv_unlock(tbo->base.resv);
> +
> return ret;
> }
>
> @@ -1254,6 +1297,7 @@ 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 +2308,25 @@ 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;
> + struct xe_device *xe = ttm_to_xe_device(bdev);
> +
> + drm_vma_node_unmap(&tbo->base.vma_node, bdev->dev_mapping);
> +
> + /*
> + * Other callers xe_ttm_bo_destroy and xe_bo_move_notify also checks and
> + * deletes vram_user_fault_link so grabbing spinlock here.
> + */
> + XE_WARN_ON(!bo->vram_userfault_count);
> + spin_lock(&xe->mem_access.vram_userfault_lock);
AFAICT exclusive access is needed for the entire list op, including the
list iteration prior to this.
> + list_del(&bo->vram_userfault_link);
> + bo->vram_userfault_count = 0;
> + spin_unlock(&xe->mem_access.vram_userfault_lock);
> +}
> +
> #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..910b35c05acd 100644
> --- a/drivers/gpu/drm/xe/xe_bo_types.h
> +++ b/drivers/gpu/drm/xe/xe_bo_types.h
> @@ -88,6 +88,11 @@ struct xe_bo {
> * objects.
> */
> u16 cpu_caching;
> + /**
> + * Whether the object is currently in fake offset mmap backed by vram.
> + */
> + unsigned int vram_userfault_count;
> + struct list_head vram_userfault_link;
Nit: Needs proper kernel-doc. Also consider maybe wrapping this in a struct:
struct {
struct list_head link;
int count;
} vram_userfault;
> };
>
> #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..6890d21f7a4c 100644
> --- a/drivers/gpu/drm/xe/xe_device_types.h
> +++ b/drivers/gpu/drm/xe/xe_device_types.h
> @@ -385,6 +385,26 @@ struct xe_device {
> struct {
> /** @ref: ref count of memory accesses */
> atomic_t ref;
> + /*
> + * Protects access to vram usefault list.
> + * It is required, if we are outside of the runtime suspend path,
> + * access to @vram_userfault_list requires always first grabbing the
> + * runtime pm, to ensure we can't race against runtime suspend.
> + * Once we have that we also need to grab @vram_userfault_lock,
> + * at which point we have exclusive access.
> + * The runtime suspend path is special since it doesn't really hold any locks,
> + * but instead has exclusive access by virtue of all other accesses requiring
> + * holding the runtime pm wakeref.
> + */
> + spinlock_t vram_userfault_lock;
> +
> + /*
> + * Keep list of userfaulted gem obj, which require to release their
> + * mmap mappings at runtime suspend path.
> + */
Nit: Not properly formatted kernel-doc here and above.
> + struct list_head vram_userfault_list;
> +
> + bool vram_userfault_ongoing;
Also maybe consider wrapping this in a struct:
struct {
spinlock_t lock;
list_head list;
} vram_userfault;
Also vram_userfault_ongoing looks to be unused.
> } mem_access;
>
> /**
> diff --git a/drivers/gpu/drm/xe/xe_pm.c b/drivers/gpu/drm/xe/xe_pm.c
> index b429c2876a76..bc1cb081e6e5 100644
> --- a/drivers/gpu/drm/xe/xe_pm.c
> +++ b/drivers/gpu/drm/xe/xe_pm.c
> @@ -181,6 +181,8 @@ void xe_pm_init(struct xe_device *xe)
> }
>
> xe_pm_runtime_init(xe);
> + INIT_LIST_HEAD(&xe->mem_access.vram_userfault_list);
> + spin_lock_init(&xe->mem_access.vram_userfault_lock);
> }
>
> void xe_pm_runtime_fini(struct xe_device *xe)
> @@ -214,6 +216,7 @@ 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 +250,10 @@ int xe_pm_runtime_suspend(struct xe_device *xe)
> */
> lock_map_acquire(&xe_device_mem_access_lockdep_map);
>
> + list_for_each_entry_safe(bo, on,
> + &xe->mem_access.vram_userfault_list, vram_userfault_link)
> + xe_bo_runtime_pm_release_mmap_offset(bo);
> +
> if (xe->d3cold.allowed) {
> err = xe_bo_evict_all(xe);
> if (err)
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