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[vhost,v3,23/24] vdpa/mlx5: Don't reset VQs more than necessary

Message ID 20240708-stage-vdpa-vq-precreate-v3-23-afe3c766e393@nvidia.com (mailing list archive)
State Not Applicable
Headers show
Series vdpa/mlx5: Pre-create HW VQs to reduce LM downtime | expand

Checks

Context Check Description
netdev/tree_selection success Not a local patch

Commit Message

Dragos Tatulea July 8, 2024, noon UTC 
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.

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

Patch

diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
index f2af0ba82dd2..4e464a22381b 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);
-	mvqs_set_defaults(ndev);
+	vq_reset = needs_vqs_reset(mvdev);
+	if (vq_reset) {
+		teardown_vq_resources(ndev);
+		mvqs_set_defaults(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;