drm/xe/madvise: Block imported and exported dma-bufs

Prevent marking imported or exported dma-bufs as purgeable.
External devices may be accessing these buffers without our
knowledge, making purging unsafe.

Check drm_gem_is_imported() for buffers created by other
drivers and obj->dma_buf for buffers exported to other
drivers. Silently skip these BOs during madvise processing.

This follows drm_gem_shmem's purgeable implementation and
prevents data corruption from purging actively-used shared
buffers.

Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Arvind Yadav <arvind.yadav@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patch.msgid.link/20260326130843.3545241-8-arvind.yadav@intel.com

diff --git a/drivers/gpu/drm/xe/xe_vm_madvise.c b/drivers/gpu/drm/xe/xe_vm_madvise.c
index 991bbd6a7ff3441a4a7183eecd527dfba7984510..b7c1c1c525b20fa7e9fce200e26026d8743060df 100644 (file)
--- a/drivers/gpu/drm/xe/xe_vm_madvise.c
+++ b/drivers/gpu/drm/xe/xe_vm_madvise.c
@@ -185,6 +185,33 @@ static void madvise_pat_index(struct xe_device *xe, struct xe_vm *vm,
        }
 }
 
+/**
+ * xe_bo_is_dmabuf_shared() - Check if BO is shared via dma-buf
+ * @bo: Buffer object
+ *
+ * Prevent marking imported or exported dma-bufs as purgeable.
+ * For imported BOs, Xe doesn't own the backing store and cannot
+ * safely reclaim pages (exporter or other devices may still be
+ * using them). For exported BOs, external devices may have active
+ * mappings we cannot track.
+ *
+ * Return: true if BO is imported or exported, false otherwise
+ */
+static bool xe_bo_is_dmabuf_shared(struct xe_bo *bo)
+{
+       struct drm_gem_object *obj = &bo->ttm.base;
+
+       /* Imported: exporter owns backing store */
+       if (drm_gem_is_imported(obj))
+               return true;
+
+       /* Exported: external devices may be accessing */
+       if (obj->dma_buf)
+               return true;
+
+       return false;
+}
+
 /**
  * enum xe_bo_vmas_purge_state - VMA purgeable state aggregation
  *
@@ -234,6 +261,10 @@ static enum xe_bo_vmas_purge_state xe_bo_all_vmas_dontneed(struct xe_bo *bo)
 
        xe_bo_assert_held(bo);
 
+       /* Shared dma-bufs cannot be purgeable */
+       if (xe_bo_is_dmabuf_shared(bo))
+               return XE_BO_VMAS_STATE_WILLNEED;
+
        drm_gem_for_each_gpuvm_bo(vm_bo, obj) {
                drm_gpuvm_bo_for_each_va(gpuva, vm_bo) {
                        struct xe_vma *vma = gpuva_to_vma(gpuva);
@@ -335,6 +366,12 @@ static void __maybe_unused madvise_purgeable(struct xe_device *xe,
                /* BO must be locked before modifying madv state */
                xe_bo_assert_held(bo);
 
+               /* Skip shared dma-bufs - no PTEs to zap */
+               if (xe_bo_is_dmabuf_shared(bo)) {
+                       vmas[i]->skip_invalidation = true;
+                       continue;
+               }
+
                /*
                 * Once purged, always purged. Cannot transition back to WILLNEED.
                 * This matches i915 semantics where purged BOs are permanently invalid.