[PATCH v2 09/15] drm/xe: Invalidate existing VRAM mappings on wedge

[Arvind Yadav <arvind.yadav@intel.com>]

CPU mappings created before a device wedge can keep valid PTEs and
continue accessing VRAM. Mapping new faults to a dummy page does not
replace these existing mappings.

Use the common device I/O SRCU gate to wait for active CPU faults to
finish. Then invalidate all tracked VRAM mappings. Faults starting
after the wedge use the per-BO dummy page.

This ensures userspace is notified only after existing VRAM mappings
have been removed.

v2:
- Drain active faults before invalidating VRAM mappings

Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Arvind Yadav <arvind.yadav@intel.com>
---
 drivers/gpu/drm/xe/xe_bo.c     | 20 ++++++++++++++++++++
 drivers/gpu/drm/xe/xe_bo.h     |  1 +
 drivers/gpu/drm/xe/xe_device.c |  4 ++++
 3 files changed, 25 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
index 7902ce3fe012..73dcd397dc13 100644
--- a/drivers/gpu/drm/xe/xe_bo.c
+++ b/drivers/gpu/drm/xe/xe_bo.c
@@ -4155,6 +4155,26 @@ void xe_bo_runtime_pm_release_mmap_offset(struct xe_bo *bo)
 	list_del_init(&bo->vram_userfault_link);
 }
 
+/**
+ * xe_bo_wedged_invalidate_mmaps - Invalidate CPU mappings backed by VRAM
+ * @xe: xe device instance
+ *
+ * The caller must drain the common device I/O gate before calling this
+ * function. Remove all tracked VRAM mappings so later faults map the
+ * per-BO dummy page.
+ */
+void xe_bo_wedged_invalidate_mmaps(struct xe_device *xe)
+{
+	struct xe_bo *bo, *next;
+
+	mutex_lock(&xe->mem_access.vram_userfault.lock);
+	list_for_each_entry_safe(bo, next,
+				 &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 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 290ca624e2a7..103eaacb56f2 100644
--- a/drivers/gpu/drm/xe/xe_bo.h
+++ b/drivers/gpu/drm/xe/xe_bo.h
@@ -449,6 +449,7 @@ int xe_gem_create_ioctl(struct drm_device *dev, void *data,
 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);
+void xe_bo_wedged_invalidate_mmaps(struct xe_device *xe);
 
 int xe_bo_dumb_create(struct drm_file *file_priv,
 		      struct drm_device *dev,
diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
index 045b5844e5c3..3549cf89a353 100644
--- a/drivers/gpu/drm/xe/xe_device.c
+++ b/drivers/gpu/drm/xe/xe_device.c
@@ -896,6 +896,10 @@ static void xe_device_wedged_work(struct work_struct *work)
 	unsigned long method;
 	int err;
 
+	/* Drain active faults before invalidating VRAM mappings. */
+	xe_device_io_drain(xe);
+	xe_bo_wedged_invalidate_mmaps(xe);
+
 	/* Report at most one recovery method per worker invocation. */
 	method = READ_ONCE(xe->wedged.method);
 	if (method != READ_ONCE(xe->wedged.reported_method)) {
-- 
2.43.0