From: Felix Kuehling <[email protected]>

[ Upstream commit 90ca78deb004abe75b5024968a199acb96bb70f9 ]

This fixes an intermittent bug where a root PD clear operation still in
progress could overwrite a PDE update done by the CPU, resulting in a
VM fault.

Fixes: 108b4d928c03 ("drm/amd/amdgpu: Update VM function pointer")
Reported-by: Jay Cornwall <[email protected]>
Tested-by: Jay Cornwall <[email protected]>
Signed-off-by: Felix Kuehling <[email protected]>
Reviewed-by: Christian König <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index c7514f743409..6335bd4ae374 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -2867,10 +2867,17 @@ int amdgpu_vm_make_compute(struct amdgpu_device *adev, 
struct amdgpu_vm *vm, uns
        WARN_ONCE((vm->use_cpu_for_update && 
!amdgpu_gmc_vram_full_visible(&adev->gmc)),
                  "CPU update of VM recommended only for large BAR system\n");
 
-       if (vm->use_cpu_for_update)
+       if (vm->use_cpu_for_update) {
+               /* Sync with last SDMA update/clear before switching to CPU */
+               r = amdgpu_bo_sync_wait(vm->root.base.bo,
+                                       AMDGPU_FENCE_OWNER_UNDEFINED, true);
+               if (r)
+                       goto free_idr;
+
                vm->update_funcs = &amdgpu_vm_cpu_funcs;
-       else
+       } else {
                vm->update_funcs = &amdgpu_vm_sdma_funcs;
+       }
        dma_fence_put(vm->last_update);
        vm->last_update = NULL;
 
-- 
2.25.1



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