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Subject[PATCH] vdpa/mlx5: set_features should allow reset to zero
Date
Commit 452639a64ad8 ("vdpa: make sure set_features is invoked
for legacy") made an exception for legacy guests to reset
features to 0, when config space is accessed before features
are set. We should relieve the verify_min_features() check
and allow features reset to 0 for this case.

It's worth noting that not just legacy guests could access
config space before features are set. For instance, when
feature VIRTIO_NET_F_MTU is advertised some modern driver
will try to access and validate the MTU present in the config
space before virtio features are set. Rejecting reset to 0
prematurely causes correct MTU and link status unable to load
for the very first config space access, rendering issues like
guest showing inaccurate MTU value, or failure to reject
out-of-range MTU.

Fixes: 1a86b377aa21 ("vdpa/mlx5: Add VDPA driver for supported mlx5 devices")
Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
---
drivers/vdpa/mlx5/net/mlx5_vnet.c | 15 +--------------
1 file changed, 1 insertion(+), 14 deletions(-)

diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
index 7c1f789..540dd67 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
@@ -1490,14 +1490,6 @@ static u64 mlx5_vdpa_get_features(struct vdpa_device *vdev)
return mvdev->mlx_features;
}

-static int verify_min_features(struct mlx5_vdpa_dev *mvdev, u64 features)
-{
- if (!(features & BIT_ULL(VIRTIO_F_ACCESS_PLATFORM)))
- return -EOPNOTSUPP;
-
- return 0;
-}
-
static int setup_virtqueues(struct mlx5_vdpa_net *ndev)
{
int err;
@@ -1558,18 +1550,13 @@ static int mlx5_vdpa_set_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);
- int err;

print_features(mvdev, features, true);

- err = verify_min_features(mvdev, features);
- if (err)
- return err;
-
ndev->mvdev.actual_features = features & ndev->mvdev.mlx_features;
ndev->config.mtu = cpu_to_mlx5vdpa16(mvdev, ndev->mtu);
ndev->config.status |= cpu_to_mlx5vdpa16(mvdev, VIRTIO_NET_S_LINK_UP);
- return err;
+ return 0;
}

static void mlx5_vdpa_set_config_cb(struct vdpa_device *vdev, struct vdpa_callback *cb)
--
1.8.3.1
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