drm/pagemap, drm/xe: Ensure that the devmem allocation is idle before use

In situations where no system memory is migrated to devmem, and in
upcoming patches where another GPU is performing the migration to
the newly allocated devmem buffer, there is nothing to ensure any
ongoing clear to the devmem allocation or async eviction from the
devmem allocation is complete.

Address that by passing a struct dma_fence down to the copy
functions, and ensure it is waited for before migration is marked
complete.

v3:
- New patch.
v4:
- Update the logic used for determining when to wait for the
  pre_migrate_fence.
- Update the logic used for determining when to warn for the
  pre_migrate_fence since the scheduler fences apparently
  can signal out-of-order.
v5:
- Fix a UAF (CI)
- Remove references to source P2P migration (Himal)
- Put the pre_migrate_fence after migration.
v6:
- Pipeline the pre_migrate_fence dependency (Matt Brost)

Fixes: c5b3eb5a906c ("drm/xe: Add GPUSVM device memory copy vfunc functions")
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: <stable@vger.kernel.org> # v6.15+
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> # For merging through drm-xe.
Link: https://patch.msgid.link/20251219113320.183860-4-thomas.hellstrom@linux.intel.com
(cherry picked from commit 16b5ad31952476fb925c401897fc171cd37f536b)
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>

1 files changed, 14 insertions, 3 deletions

diff --git a/include/drm/drm_pagemap.h b/include/drm/drm_pagemap.h
index f6e7e234c089..70a7991f784f 100644
--- a/include/drm/drm_pagemap.h
+++ b/include/drm/drm_pagemap.h
@@ -8,6 +8,7 @@
 
 #define NR_PAGES(order) (1U << (order))
 
+struct dma_fence;
 struct drm_pagemap;
 struct drm_pagemap_zdd;
 struct device;
@@ -174,6 +175,8 @@ struct drm_pagemap_devmem_ops {
 	 * @pages: Pointer to array of device memory pages (destination)
 	 * @pagemap_addr: Pointer to array of DMA information (source)
 	 * @npages: Number of pages to copy
+	 * @pre_migrate_fence: dma-fence to wait for before migration start.
+	 * May be NULL.
 	 *
 	 * Copy pages to device memory. If the order of a @pagemap_addr entry
 	 * is greater than 0, the entry is populated but subsequent entries
@@ -183,13 +186,16 @@ struct drm_pagemap_devmem_ops {
 	 */
 	int (*copy_to_devmem)(struct page **pages,
 			      struct drm_pagemap_addr *pagemap_addr,
-			      unsigned long npages);
+			      unsigned long npages,
+			      struct dma_fence *pre_migrate_fence);
 
 	/**
 	 * @copy_to_ram: Copy to system RAM (required for migration)
 	 * @pages: Pointer to array of device memory pages (source)
 	 * @pagemap_addr: Pointer to array of DMA information (destination)
 	 * @npages: Number of pages to copy
+	 * @pre_migrate_fence: dma-fence to wait for before migration start.
+	 * May be NULL.
 	 *
 	 * Copy pages to system RAM. If the order of a @pagemap_addr entry
 	 * is greater than 0, the entry is populated but subsequent entries
@@ -199,7 +205,8 @@ struct drm_pagemap_devmem_ops {
 	 */
 	int (*copy_to_ram)(struct page **pages,
 			   struct drm_pagemap_addr *pagemap_addr,
-			   unsigned long npages);
+			   unsigned long npages,
+			   struct dma_fence *pre_migrate_fence);
 };
 
 /**
@@ -212,6 +219,8 @@ struct drm_pagemap_devmem_ops {
  * @dpagemap: The struct drm_pagemap of the pages this allocation belongs to.
  * @size: Size of device memory allocation
  * @timeslice_expiration: Timeslice expiration in jiffies
+ * @pre_migrate_fence: Fence to wait for or pipeline behind before migration starts.
+ * (May be NULL).
  */
 struct drm_pagemap_devmem {
 	struct device *dev;
@@ -221,6 +230,7 @@ struct drm_pagemap_devmem {
 	struct drm_pagemap *dpagemap;
 	size_t size;
 	u64 timeslice_expiration;
+	struct dma_fence *pre_migrate_fence;
 };
 
 int drm_pagemap_migrate_to_devmem(struct drm_pagemap_devmem *devmem_allocation,
@@ -238,7 +248,8 @@ struct drm_pagemap *drm_pagemap_page_to_dpagemap(struct page *page);
 void drm_pagemap_devmem_init(struct drm_pagemap_devmem *devmem_allocation,
 			     struct device *dev, struct mm_struct *mm,
 			     const struct drm_pagemap_devmem_ops *ops,
-			     struct drm_pagemap *dpagemap, size_t size);
+			     struct drm_pagemap *dpagemap, size_t size,
+			     struct dma_fence *pre_migrate_fence);
 
 int drm_pagemap_populate_mm(struct drm_pagemap *dpagemap,
 			    unsigned long start, unsigned long end,