drm/xe: Wait on external BO kernel fences in exec IOCTL

Before arming a user job, xe_exec_ioctl() only added the VM's
dma-resv KERNEL slot as a dependency. That slot covers rebinds and
the kernel operations of the VM's private BOs, but not external BOs
(bo->vm == NULL), which carry their kernel operations (evictions,
moves, ...) in their own dma-resv KERNEL slot.

The DMA_RESV_USAGE_KERNEL slot is the cross-driver contract for
memory management operations that must complete before the BO or its
backing store may be used: any accessor is required to wait on the
KERNEL fences before touching the resv. By skipping the external BOs'
KERNEL slots, the exec path violated that contract and could schedule
a user job while a kernel operation on an external BO mapped by the VM
was still in flight, racing against it and potentially reading or
writing memory that was being moved.

Replace the VM-only dependency with an iteration over every object
locked by the exec, adding each object's KERNEL slot as a job
dependency. This covers the VM resv (rebinds and private BOs) as well
as every external BO, mirroring the drm_gpuvm_resv_add_fence() call
that later publishes the job fence to the same set of objects.
Long-running mode continues to skip this, as before.

Fixes: dd08ebf6c352 ("drm/xe: Introduce a new DRM driver for Intel GPUs")
Cc: stable@vger.kernel.org
Assisted-by: GitHub_Copilot:claude-opus-4.8
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patch.msgid.link/20260702215805.4011228-1-matthew.brost@intel.com
(cherry picked from commit a6b842acf3ddd1efc53a56de9260cfa718fb35e7)
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>

diff --git a/drivers/gpu/drm/xe/xe_exec.c b/drivers/gpu/drm/xe/xe_exec.c
index e05dabfcd43ca8ac9cc633db4933f095470f5989..d5293bc33a670d06f6fb230014744ee27aab8f42 100644 (file)
--- a/drivers/gpu/drm/xe/xe_exec.c
+++ b/drivers/gpu/drm/xe/xe_exec.c
@@ -292,13 +292,23 @@ retry:
                goto err_exec;
        }
 
-       /* Wait behind rebinds */
+       /*
+        * Wait behind rebinds and any kernel operations (evictions, defrag
+        * moves, ...) on the VM and all external BOs. The VM's private BOs
+        * carry their kernel ops in the VM dma-resv KERNEL slot, while each
+        * external BO carries them in its own dma-resv KERNEL slot; both are
+        * covered by iterating every object locked by the exec, mirroring the
+        * drm_gpuvm_resv_add_fence() below.
+        */
        if (!xe_vm_in_lr_mode(vm)) {
-               err = xe_sched_job_add_deps(job,
-                                           xe_vm_resv(vm),
-                                           DMA_RESV_USAGE_KERNEL);
-               if (err)
-                       goto err_put_job;
+               struct drm_gem_object *obj;
+
+               drm_exec_for_each_locked_object(exec, obj) {
+                       err = xe_sched_job_add_deps(job, obj->resv,
+                                                   DMA_RESV_USAGE_KERNEL);
+                       if (err)
+                               goto err_put_job;
+               }
        }
 
        for (i = 0; i < num_syncs && !err; i++)