[PATCH v2 15/15] drm/xe: Block BO VM access when device I/O is unavailable

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

xe_bo_vm_access() may acquire a runtime PM reference and access a BO
during PCI error recovery, after a permanent wedge or during device
unplug.

Use xe_device_io_get() to protect against unplug, PCI error recovery and
permanent wedging. Keep both protections until the runtime PM reference
has been released.

Return -EIO for a permanent wedge, -ECANCELED during PCI error recovery
and -ENODEV after device unplug.

v2:
 - Replace the runtime-PM scoped guard with explicit get/put calls
   to avoid mixing scope-based and goto-based cleanup. (Sashiko)
 - Replace the private VRAM SRCU lock with the common device I/O gate.
 - Preserve -EIO for BO access after a permanent wedge.

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 | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
index 73dcd397dc13..5372bc07aa4e 100644
--- a/drivers/gpu/drm/xe/xe_bo.c
+++ b/drivers/gpu/drm/xe/xe_bo.c
@@ -2235,9 +2235,18 @@ static int xe_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
 	struct ttm_buffer_object *ttm_bo = vma->vm_private_data;
 	struct xe_bo *bo = ttm_to_xe_bo(ttm_bo);
 	struct xe_device *xe = xe_bo_device(bo);
+	int idx, ret;
 
-	guard(xe_pm_runtime)(xe);
-	return ttm_bo_vm_access(vma, addr, buf, len, write);
+	ret = xe_device_io_get(xe, &idx);
+	if (ret)
+		return ret == -ECANCELED && xe_device_wedged(xe) ? -EIO : ret;
+
+	xe_pm_runtime_get(xe);
+	ret = ttm_bo_vm_access(vma, addr, buf, len, write);
+	xe_pm_runtime_put(xe);
+
+	xe_device_io_put(idx);
+	return ret;
 }
 
 /**
-- 
2.43.0