[PATCH vhost 22/23] vdpa/mlx5: Don't reset VQs more than necessary

Dragos Tatulea
2024-06-17T15:09:33Z

The vdpa device can be reset many times in sequence without any
significant state changes in between. Previously this was not a problem:
VQs were torn down only on first reset. But after VQ pre-creation was
introduced, each reset will delete and re-create the hardware VQs and
their associated resources.

To solve this problem, avoid resetting hardware VQs if the VQs are still
in a blank state.

Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
---
drivers/vdpa/mlx5/net/mlx5_vnet.c | 30 +++++++++++++++++++++++++++---
1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
index d80d6b47da61..1a5ee0d2b47f 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
@@ -3134,18 +3134,41 @@ static void init_group_to_asid_map(struct mlx5_vdpa_dev *mvdev)
mvdev->group2asid[i] = 0;
}

+static bool needs_vqs_reset(const struct mlx5_vdpa_dev *mvdev)
+{
+ struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
+ struct mlx5_vdpa_virtqueue *mvq = &ndev->vqs[0];
+
+ if (mvdev->status & VIRTIO_CONFIG_S_DRIVER_OK)
+ return true;
+
+ if (mvq->fw_state != MLX5_VIRTIO_NET_Q_OBJECT_STATE_INIT)
+ return true;
+
+ return mvq->modified_fields & (
+ MLX5_VIRTQ_MODIFY_MASK_STATE |
+ MLX5_VIRTQ_MODIFY_MASK_VIRTIO_Q_ADDRS |
+ MLX5_VIRTQ_MODIFY_MASK_VIRTIO_Q_AVAIL_IDX |
+ MLX5_VIRTQ_MODIFY_MASK_VIRTIO_Q_USED_IDX
+ );
+}
+
static int mlx5_vdpa_compat_reset(struct vdpa_device *vdev, u32 flags)
{
struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
+ bool vq_reset;

print_status(mvdev, 0, true);
mlx5_vdpa_info(mvdev, "performing device reset\n");

down_write(&ndev->reslock);
unregister_link_notifier(ndev);
- teardown_vq_resources(ndev);
- init_mvqs(ndev);
+ vq_reset = needs_vqs_reset(mvdev);
+ if (vq_reset) {
+ teardown_vq_resources(ndev);
+ init_mvqs(ndev);
+ }

if (flags & VDPA_RESET_F_CLEAN_MAP)
mlx5_vdpa_destroy_mr_resources(&ndev->mvdev);
@@ -3165,7 +3188,8 @@ static int mlx5_vdpa_compat_reset(struct vdpa_device *vdev, u32 flags)
if (mlx5_vdpa_create_dma_mr(mvdev))
mlx5_vdpa_warn(mvdev, "create MR failed\n");
}
- setup_vq_resources(ndev, false);
+ if (vq_reset)
+ setup_vq_resources(ndev, false);
up_write(&ndev->reslock);

return 0;

--
2.45.1