[PATCH vhost v2 22/24] vdpa/mlx5: Re-create HW VQs under certain conditions

[Dragos Tatulea]

There are a few conditions under which the hardware VQs need a full
teardown and setup:

- VQ size changed to something else than default value. Hardware VQ size
  modification is not supported.

- User turns off certain device features: mergeable buffers, checksum
  virtio 1.0 compliance. In these cases, the TIR and RQT need to be
  re-created.

Add a needs_teardown configuration variable and set it when detecting
the above scenarios. On next DRIVER_OK, the resources will be torn down
first.

Reviewed-by: Cosmin Ratiu <cra...@nvidia.com>
Acked-by: Eugenio Pérez <epere...@redhat.com>
Signed-off-by: Dragos Tatulea <dtatu...@nvidia.com>
---
 drivers/vdpa/mlx5/net/mlx5_vnet.c | 15 +++++++++++++++
 drivers/vdpa/mlx5/net/mlx5_vnet.h |  1 +
 2 files changed, 16 insertions(+)

diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c 
b/drivers/vdpa/mlx5/net/mlx5_vnet.c
index 8ef703f4c23d..ea4bfd9afce9 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
@@ -2390,6 +2390,7 @@ 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;
        mvq->num_ent = num;
 }
 
@@ -2800,6 +2801,7 @@ static int mlx5_vdpa_set_driver_features(struct 
vdpa_device *vdev, u64 features)
        struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
        struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
        u64 old_features = mvdev->actual_features;
+       u64 diff_features;
        int err;
 
        print_features(mvdev, features, true);
@@ -2822,6 +2824,14 @@ static int mlx5_vdpa_set_driver_features(struct 
vdpa_device *vdev, u64 features)
                }
        }
 
+       /* When below features diverge from initial device features, VQs need a 
full teardown. */
+#define NEEDS_TEARDOWN_MASK (BIT_ULL(VIRTIO_NET_F_MRG_RXBUF) | \
+                            BIT_ULL(VIRTIO_NET_F_CSUM) | \
+                            BIT_ULL(VIRTIO_F_VERSION_1))
+
+       diff_features = mvdev->mlx_features ^ mvdev->actual_features;
+       ndev->needs_teardown = !!(diff_features & NEEDS_TEARDOWN_MASK);
+
        update_cvq_info(mvdev);
        return err;
 }
@@ -3038,6 +3048,7 @@ static void teardown_vq_resources(struct mlx5_vdpa_net 
*ndev)
        destroy_rqt(ndev);
        teardown_virtqueues(ndev);
        ndev->setup = false;
+       ndev->needs_teardown = false;
 }
 
 static int setup_cvq_vring(struct mlx5_vdpa_dev *mvdev)
@@ -3078,6 +3089,10 @@ static void mlx5_vdpa_set_status(struct vdpa_device 
*vdev, u8 status)
                                goto err_setup;
                        }
                        register_link_notifier(ndev);
+
+                       if (ndev->needs_teardown)
+                               teardown_vq_resources(ndev);
+
                        if (ndev->setup) {
                                err = resume_vqs(ndev);
                                if (err) {
diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.h 
b/drivers/vdpa/mlx5/net/mlx5_vnet.h
index 90b556a57971..00e79a7d0be8 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.h
+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.h
@@ -56,6 +56,7 @@ struct mlx5_vdpa_net {
        struct dentry *rx_dent;
        struct dentry *rx_table_dent;
        bool setup;
+       bool needs_teardown;
        u32 cur_num_vqs;
        u32 rqt_size;
        bool nb_registered;

-- 
2.45.1