[PATCH 5.4 128/261] drm/amdgpu: Sync with VM root BO when switching VM to CPU update mode

[Greg Kroah-Hartman]

From: Felix Kuehling <Felix.Kuehling@xxxxxxx>

[ 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 <Jay.Cornwall@xxxxxxx>
Tested-by: Jay Cornwall <Jay.Cornwall@xxxxxxx>
Signed-off-by: Felix Kuehling <Felix.Kuehling@xxxxxxx>
Reviewed-by: Christian KÃnig <christian.koenig@xxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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