[Intel-xe] [RFC PATCH] drm/xe/dgfx: Release mmap mappings on rpm suspend
Rodrigo Vivi
rodrigo.vivi at intel.com
Fri Sep 22 14:28:23 UTC 2023
On Thu, Aug 24, 2023 at 11:16:18PM +0530, 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.
>
> 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 | 53 ++++++++++++++++++++++++++--
> drivers/gpu/drm/xe/xe_bo.h | 2 ++
> drivers/gpu/drm/xe/xe_bo_types.h | 6 ++++
> drivers/gpu/drm/xe/xe_device_types.h | 20 +++++++++++
> drivers/gpu/drm/xe/xe_pm.c | 7 ++++
> 5 files changed, 85 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
> index 1ab682d61e3c..4192bfcd8013 100644
> --- a/drivers/gpu/drm/xe/xe_bo.c
> +++ b/drivers/gpu/drm/xe/xe_bo.c
> @@ -776,6 +776,18 @@ static int xe_bo_move(struct ttm_buffer_object *ttm_bo, bool evict,
> dma_fence_put(fence);
> }
>
> + /*
> + * 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);
I'm always afraid of these locking interactions here, but I believe
this is okay.
> + }
> +
> xe_device_mem_access_put(xe);
> trace_printk("new_mem->mem_type=%d\n", new_mem->mem_type);
>
> @@ -1100,6 +1112,8 @@ 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 = ttm_to_xe_bo(tbo);
hmm...
> + struct xe_device *xe = to_xe_device(ddev);
> vm_fault_t ret;
> int idx, r = 0;
>
> @@ -1107,9 +1121,10 @@ static vm_fault_t xe_gem_fault(struct vm_fault *vmf)
> if (ret)
> return ret;
>
> - if (drm_dev_enter(ddev, &idx)) {
> - struct xe_bo *bo = ttm_to_xe_bo(tbo);
... if this was here, maybe there's a reason to avoid getting the bo only
if drm_dev_enter has succeeded?
I would at least keep this call here inside the drm_dev_enter block
and not move that up there.
> + if (tbo->resource->bus.is_iomem)
But I also wonder if it is safe at all to access the tbo pointers
on that case... should we move that inside drm_dev_enter? or that
is too late?
> + xe_device_mem_access_get(xe);
>
> + if (drm_dev_enter(ddev, &idx)) {
> trace_xe_bo_cpu_fault(bo);
>
> if (should_migrate_to_system(bo)) {
> @@ -1127,10 +1142,25 @@ 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_rpm;
> + /*
> + * ttm_bo_vm_reserve() already has dma_resv_lock.
could we add some lockdep assertion here?
> + * vram_userfault_count is protected by dma_resv lock and rpm wakeref.
> + */
> + if (ret == VM_FAULT_NOPAGE && xe_device_mem_access_ongoing(xe) && !bo->vram_userfault_count) {
> + 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_WARN_ON(!tbo->resource->bus.is_iomem);
> + }
> dma_resv_unlock(tbo->base.resv);
> +out_rpm:
> + if(tbo->resource->bus.is_iomem && xe_device_mem_access_ongoing(xe))
> + xe_device_mem_access_put(xe);
> return ret;
> }
>
> @@ -2108,6 +2138,23 @@ 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);
> +
> + /*
> + * We have exclusive access here via runtime suspend. All other callers
> + * must first grab the rpm wakeref.
> + */
> + XE_WARN_ON(!bo->vram_userfault_count);
> + list_del(&bo->vram_userfault_link);
> + bo->vram_userfault_count = 0;
> +}
> +
> +
> #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 0823dda0f31b..6b86f326c700 100644
> --- a/drivers/gpu/drm/xe/xe_bo.h
> +++ b/drivers/gpu/drm/xe/xe_bo.h
> @@ -247,6 +247,8 @@ 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 f6ee920303af..cdca91a378c4 100644
> --- a/drivers/gpu/drm/xe/xe_bo_types.h
> +++ b/drivers/gpu/drm/xe/xe_bo_types.h
> @@ -68,6 +68,12 @@ struct xe_bo {
> struct llist_node freed;
> /** @created: Whether the bo has passed initial creation */
> bool created;
> + /**
> + * Whether the object is currently in fake offset mmap backed by vram.
> + */
> + unsigned int vram_userfault_count;
> + struct list_head vram_userfault_link;
> +
> };
>
> #endif
> diff --git a/drivers/gpu/drm/xe/xe_device_types.h b/drivers/gpu/drm/xe/xe_device_types.h
> index 750e1f0d3339..c345fb483af1 100644
> --- a/drivers/gpu/drm/xe/xe_device_types.h
> +++ b/drivers/gpu/drm/xe/xe_device_types.h
> @@ -328,6 +328,26 @@ 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.
> + */
> + struct list_head vram_userfault_list;
> +
> + bool vram_userfault_ongoing;
> } mem_access;
>
> /** @d3cold: Encapsulate d3cold related stuff */
> diff --git a/drivers/gpu/drm/xe/xe_pm.c b/drivers/gpu/drm/xe/xe_pm.c
> index 0f06d8304e17..51cde1db930e 100644
> --- a/drivers/gpu/drm/xe/xe_pm.c
> +++ b/drivers/gpu/drm/xe/xe_pm.c
> @@ -172,6 +172,8 @@ 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)
> @@ -205,6 +207,7 @@ 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;
> @@ -238,6 +241,10 @@ 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);
> +
other then the comments above I believe we should get the test that Anshuman
just sent, tweak it to ensure we cover this case and then give it a try.
> if (xe->d3cold.allowed) {
> err = xe_bo_evict_all(xe);
> if (err)
> --
> 2.25.1
>
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