From: Eli Cohen elic@nvidia.com
[ Upstream commit 83ef73b27eb2363f44faf9c3ee28a3fe752cfd15 ]
Make sure to put dma write memory barrier after updating CQ consumer index so the hardware knows that there are available CQE slots in the queue.
Failure to do this can cause the update of the RX doorbell record to get updated before the CQ consumer index resulting in CQ overrun.
Fixes: 1a86b377aa21 ("vdpa/mlx5: Add VDPA driver for supported mlx5 devices") Signed-off-by: Eli Cohen elic@nvidia.com Link: https://lore.kernel.org/r/20201209140004.15892-1-elic@nvidia.com Signed-off-by: Michael S. Tsirkin mst@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/vdpa/mlx5/net/mlx5_vnet.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c index 1fa6fcac82992..81b932f72e103 100644 --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c @@ -464,6 +464,11 @@ static int mlx5_vdpa_poll_one(struct mlx5_vdpa_cq *vcq) static void mlx5_vdpa_handle_completions(struct mlx5_vdpa_virtqueue *mvq, int num) { mlx5_cq_set_ci(&mvq->cq.mcq); + + /* make sure CQ cosumer update is visible to the hardware before updating + * RX doorbell record. + */ + dma_wmb(); rx_post(&mvq->vqqp, num); if (mvq->event_cb.callback) mvq->event_cb.callback(mvq->event_cb.private);