[PATCH 4/4] drm/xe: destroy userptr vma on UNMAP event

[Oak Zeng <oak.zeng@intel.com>]

When there is MMU_NOTIFY_UNMAP event happens, the userptr
is munmapped from CPU. There is no need to keep the xe_vma
for this userptr from GPU side. So we destroy it.

But we can't destroy vma directly from the mmu notifier
callback function, because we need to remove mmu
notifier during vma destroy. If we remove mmu notifier
directly from mmu notifier callback, it is a deadlock.
xe_vma_destroy is modified to destroy vma in a worker
thread.

Another reason of this change is, for the future
hmmptr codes, we destroy vma when hmmptr is unmapped
from CPU. We want to unify the hmmptr and userptr
code.

I believe this is also the correct behavior for userptr.
This patch is experimental for CI and open to discuss

Signed-off-by: Oak Zeng <oak.zeng@intel.com>
---
 drivers/gpu/drm/xe/xe_vm.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
index 11a4bb9d5415..90d1163c1090 100644
--- a/drivers/gpu/drm/xe/xe_vm.c
+++ b/drivers/gpu/drm/xe/xe_vm.c
@@ -40,6 +40,8 @@
 #include "xe_wa.h"
 #include "xe_hmm.h"
 
+static void xe_vma_destroy(struct xe_vma *vma, struct dma_fence *fence);
+
 static struct drm_gem_object *xe_vm_obj(struct xe_vm *vm)
 {
 	return vm->gpuvm.r_obj;
@@ -604,6 +606,9 @@ static bool vma_userptr_invalidate(struct mmu_interval_notifier *mni,
 
 	trace_xe_vma_userptr_invalidate_complete(vma);
 
+	if (range->event == MMU_NOTIFY_UNMAP)
+		xe_vma_destroy(vma, NULL);
+
 	return true;
 }
 
@@ -901,7 +906,8 @@ static void xe_vma_destroy(struct xe_vma *vma, struct dma_fence *fence)
 			xe_vma_destroy_late(vma);
 		}
 	} else {
-		xe_vma_destroy_late(vma);
+		INIT_WORK(&vma->destroy_work, vma_destroy_work_func);
+		queue_work(system_unbound_wq, &vma->destroy_work);
 	}
 }
 
-- 
2.26.3