Messages in this thread | | | Subject | Re: [PATCH] vdpa/mlx5: set_features should allow reset to zero | From | Jason Wang <> | Date | Tue, 23 Feb 2021 17:48:10 +0800 |
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On 2021/2/23 下午5:26, Michael S. Tsirkin wrote: > On Mon, Feb 22, 2021 at 08:05:26AM +0200, Eli Cohen wrote: >> On Sun, Feb 21, 2021 at 04:52:05PM -0500, Michael S. Tsirkin wrote: >>> On Sun, Feb 21, 2021 at 04:44:37PM +0200, Eli Cohen wrote: >>>> On Fri, Feb 19, 2021 at 06:54:58AM -0500, Si-Wei Liu wrote: >>>>> 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; >>>>> -} >>>>> - >>>> But what if VIRTIO_F_ACCESS_PLATFORM is not offerred? This does not >>>> support such cases. >>> Did you mean "catch such cases" rather than "support"? >>> >> Actually I meant this driver/device does not support such cases. > Well the removed code merely failed without VIRTIO_F_ACCESS_PLATFORM > it didn't actually try to support anything ...
I think it's used to catch the driver that doesn't support ACCESS_PLATFORM?
Thanks
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