[PATCH vhost] vdpa/mlx5: Fix needs_teardown flag calculation

[PATCH vhost] vdpa/mlx5: Fix needs_teardown flag calculation

[Dragos Tatulea]

needs_teardown is a device flag that indicates when virtual queues need
to be recreated. This happens for certain configuration changes: queue
size and some specific features.

Currently, the needs_teardown state can be incorrectly reset by
subsequent .set_vq_num() calls. For example, for 1 rx VQ with size 512
and 1 tx VQ with size 256:

.set_vq_num(0, 512) -> sets needs_teardown to true (rx queue has a
                       non-default size)
.set_vq_num(1, 256) -> sets needs_teardown to false (tx queue has a
                       default size)

This change takes into account the previous value of the needs_teardown
flag when re-calculating it during VQ size configuration.

Fixes: 0fe963d6fc16 ("vdpa/mlx5: Re-create HW VQs under certain conditions")
Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Reviewed-by: Shahar Shitrit <shshitrit@nvidia.com>
Reviewed-by: Si-Wei Liu <si-wei.liu@oracle.com>
Tested-by: Si-Wei Liu<si-wei.liu@oracle.com>
---
 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 cccc49a08a1a..efb5fa694f1e 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
@@ -2491,7 +2491,7 @@ static void mlx5_vdpa_set_vq_num(struct vdpa_device *vdev, u16 idx, u32 num)
         }
 
 	mvq = &ndev->vqs[idx];
-	ndev->needs_teardown = num != mvq->num_ent;
+	ndev->needs_teardown |= num != mvq->num_ent;
 	mvq->num_ent = num;
 }
 
-- 
2.43.0

Re: [PATCH vhost] vdpa/mlx5: Fix needs_teardown flag calculation

[Jason Wang]

On Thu, Jun 5, 2025 at 2:48 AM Dragos Tatulea <dtatulea@nvidia.com> wrote:
>
> needs_teardown is a device flag that indicates when virtual queues need
> to be recreated. This happens for certain configuration changes: queue
> size and some specific features.
>
> Currently, the needs_teardown state can be incorrectly reset by
> subsequent .set_vq_num() calls. For example, for 1 rx VQ with size 512
> and 1 tx VQ with size 256:
>
> .set_vq_num(0, 512) -> sets needs_teardown to true (rx queue has a
>                        non-default size)
> .set_vq_num(1, 256) -> sets needs_teardown to false (tx queue has a
>                        default size)
>
> This change takes into account the previous value of the needs_teardown
> flag when re-calculating it during VQ size configuration.
>
> Fixes: 0fe963d6fc16 ("vdpa/mlx5: Re-create HW VQs under certain conditions")
> Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
> Reviewed-by: Shahar Shitrit <shshitrit@nvidia.com>
> Reviewed-by: Si-Wei Liu <si-wei.liu@oracle.com>
> Tested-by: Si-Wei Liu<si-wei.liu@oracle.com>
> ---

Acked-by: Jason Wang <jasowang@redhat.com>

Thanks