[PATCH v2 3/3] vdpa/mlx5: defer clear_virtqueues to until DRIVER_OK

From: Si-Wei Liu
Date: Wed Feb 10 2021 - 16:51:26 EST


While virtq is stopped, get_vq_state() is supposed to
be called to get sync'ed with the latest internal
avail_index from device. The saved avail_index is used
to restate the virtq once device is started. Commit
b35ccebe3ef7 introduced the clear_virtqueues() routine
to reset the saved avail_index, however, the index
gets cleared a bit earlier before get_vq_state() tries
to read it. This would cause consistency problems when
virtq is restarted, e.g. through a series of link down
and link up events. We could defer the clearing of
avail_index to until the device is to be started,
i.e. until VIRTIO_CONFIG_S_DRIVER_OK is set again in
set_status().

Fixes: b35ccebe3ef7 ("vdpa/mlx5: Restore the hardware used index after change map")
Signed-off-by: Si-Wei Liu <si-wei.liu@xxxxxxxxxx>
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
---
drivers/vdpa/mlx5/net/mlx5_vnet.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
index 7c1f789..ce6aae8 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
@@ -1777,7 +1777,6 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
if (!status) {
mlx5_vdpa_info(mvdev, "performing device reset\n");
teardown_driver(ndev);
- clear_virtqueues(ndev);
mlx5_vdpa_destroy_mr(&ndev->mvdev);
ndev->mvdev.status = 0;
++mvdev->generation;
@@ -1786,6 +1785,7 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)

if ((status ^ ndev->mvdev.status) & VIRTIO_CONFIG_S_DRIVER_OK) {
if (status & VIRTIO_CONFIG_S_DRIVER_OK) {
+ clear_virtqueues(ndev);
err = setup_driver(ndev);
if (err) {
mlx5_vdpa_warn(mvdev, "failed to setup driver\n");
--
1.8.3.1