[PATCH 12/13] drm/amdgpu: recompute the dw estimate after allocating a new VM update job

From: YuBiao Wang <[email protected]>

amdgpu_vm_sdma_update() keeps the number of free dwords of the current
job in a local variable. When the job runs out of room it is committed
and a new one is allocated, but that local variable is not refreshed and
still describes the job which was just submitted.

The stale value is then used to decide how many PTEs fit into the new
job. If it happens to be copy_pte_num_dw + 7, or one more than that, the
result is zero. copy_pte() encodes the transfer size as count * 8 - 1,
so a count of zero asks the engine for a 1GB copy starting inside the IB
pool. That runs off the end of the pool, faults on the first unmapped
GART page above it and hangs the ring.

Re-initialize the estimate from the newly allocated job, which is empty
and therefore has its full budget available.

Cc: [email protected]
Signed-off-by: YuBiao Wang <[email protected]>
Reviewed-by: Christian König <[email protected]>
Change-Id: I2a1979b4ba9f1445c109e0cded862c36eb05015a
Signed-off-by: Alex Deucher <[email protected]>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_vm_sdma.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_sdma.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_sdma.c
index 4302742376897..4db0ff3436abc 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_sdma.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_sdma.c
@@ -254,6 +254,11 @@ static int amdgpu_vm_sdma_update(struct amdgpu_vm_update_params *p,
 						     AMDGPU_KERNEL_JOB_ID_VM_UPDATE);
 			if (r)
 				return r;
+
+			/* The estimate above describes the job which was just
+			 * submitted, take the budget of the newly allocated one.
+			 */
+			ndw = p->num_dw_left;
 		}
 
 		if (!p->pages_addr) {
-- 
2.55.0