[PATCH] vdpa/mlx5: should keep avail_index despite device status

From: Si-Wei Liu
Date: Thu Oct 01 2020 - 17:01:41 EST


A VM with mlx5 vDPA has below warnings while being reset:

vhost VQ 0 ring restore failed: -1: Resource temporarily unavailable (11)
vhost VQ 1 ring restore failed: -1: Resource temporarily unavailable (11)

We should allow userspace emulating the virtio device be
able to get to vq's avail_index, regardless of vDPA device
status. Save the index that was last seen when virtq was
stopped, so that userspace doesn't complain.

Signed-off-by: Si-Wei Liu <si-wei.liu@xxxxxxxxxx>
---
drivers/vdpa/mlx5/net/mlx5_vnet.c | 20 ++++++++++++++------
1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
index 70676a6..74264e59 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
@@ -1133,15 +1133,17 @@ static void suspend_vq(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *m
if (!mvq->initialized)
return;

- if (query_virtqueue(ndev, mvq, &attr)) {
- mlx5_vdpa_warn(&ndev->mvdev, "failed to query virtqueue\n");
- return;
- }
if (mvq->fw_state != MLX5_VIRTIO_NET_Q_OBJECT_STATE_RDY)
return;

if (modify_virtqueue(ndev, mvq, MLX5_VIRTIO_NET_Q_OBJECT_STATE_SUSPEND))
mlx5_vdpa_warn(&ndev->mvdev, "modify to suspend failed\n");
+
+ if (query_virtqueue(ndev, mvq, &attr)) {
+ mlx5_vdpa_warn(&ndev->mvdev, "failed to query virtqueue\n");
+ return;
+ }
+ mvq->avail_idx = attr.available_index;
}

static void suspend_vqs(struct mlx5_vdpa_net *ndev)
@@ -1411,8 +1413,14 @@ static int mlx5_vdpa_get_vq_state(struct vdpa_device *vdev, u16 idx, struct vdpa
struct mlx5_virtq_attr attr;
int err;

- if (!mvq->initialized)
- return -EAGAIN;
+ /* If the virtq object was destroyed, use the value saved at
+ * the last minute of suspend_vq. This caters for userspace
+ * that cares about emulating the index after vq is stopped.
+ */
+ if (!mvq->initialized) {
+ state->avail_index = mvq->avail_idx;
+ return 0;
+ }

err = query_virtqueue(ndev, mvq, &attr);
if (err) {
--
1.8.3.1