Re: [PATCH linux-next v4 6/8] vdpa/mlx5: Fix clearing of VIRTIO_NET_F_MAC feature bit

From: Jason Wang <jasowang@redhat.com>
To: Parav Pandit <parav@nvidia.com>,
	"virtualization@lists.linux-foundation.org"
	<virtualization@lists.linux-foundation.org>
Cc: Eli Cohen <elic@nvidia.com>, "mst@redhat.com" <mst@redhat.com>
Subject: Re: [PATCH linux-next v4 6/8] vdpa/mlx5: Fix clearing of VIRTIO_NET_F_MAC feature bit
Date: Tue, 26 Oct 2021 10:42:20 +0800	[thread overview]
Message-ID: <1d2a05d5-48af-89e2-ec7d-8ae0018ffa7a@redhat.com> (raw)
In-Reply-To: <PH0PR12MB5481233AF957874DF60575CEDC839@PH0PR12MB5481.namprd12.prod.outlook.com>

在 2021/10/25 下午3:08, Parav Pandit 写道:
>
>> From: Jason Wang <jasowang@redhat.com>
>> Sent: Monday, October 25, 2021 12:35 PM
>>
>> 在 2021/10/22 上午12:35, Parav Pandit 写道:
>>> Cited patch in the fixes tag clears the features bit during reset.
>>> mlx5 vdpa device feature bits are static decided by device capabilities.
>>
>> This is not what I read at least from mlx5_vdpa_get_features:
>>
>> static u64 mlx5_vdpa_get_features(struct vdpa_device *vdev) {
>>           struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
>>           struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
>>           u16 dev_features;
>>
>>           dev_features = MLX5_CAP_DEV_VDPA_EMULATION(mvdev->mdev,
>> device_features_bits_mask);
> Not sure I follow. Feature bits are decided by the device capabilities exposed by the MLX5_CAP_DEV_VDPA_EMULATION.
> Other fields below are pretty much static.

Ok, so I think in the commit log we need also mention that the 
VIRTIO_NET_F_MAC is determined and stored in device adding.

Thanks

>
>>           ndev->mvdev.mlx_features |= mlx_to_vritio_features(dev_features);
>>           if (MLX5_CAP_DEV_VDPA_EMULATION(mvdev->mdev,
>> virtio_version_1_0))
>>                   ndev->mvdev.mlx_features |= BIT_ULL(VIRTIO_F_VERSION_1);
>>           ndev->mvdev.mlx_features |= BIT_ULL(VIRTIO_F_ACCESS_PLATFORM);
>>           ndev->mvdev.mlx_features |= BIT_ULL(VIRTIO_NET_F_CTRL_VQ);
>>           ndev->mvdev.mlx_features |=
>> BIT_ULL(VIRTIO_NET_F_CTRL_MAC_ADDR);
>>           ndev->mvdev.mlx_features |= BIT_ULL(VIRTIO_NET_F_MQ);
>>
>>           print_features(mvdev, ndev->mvdev.mlx_features, false);
>>           return ndev->mvdev.mlx_features; }
>>
>>
>> Thanks
>>
>>
>>> Clearing features bit cleared the VIRTIO_NET_F_MAC. Due to this MAC
>>> address provided by the device is not honored.
>>>
>>> Fix it by not clearing the static feature bits during reset.
>>>
>>> Fixes: 0686082dbf7a ("vdpa: Add reset callback in vdpa_config_ops")
>>> Signed-off-by: Parav Pandit <parav@nvidia.com>
>>> Reviewed-by: Eli Cohen <elic@nvidia.com>
>>> ---
>>>    drivers/vdpa/mlx5/net/mlx5_vnet.c | 1 -
>>>    1 file changed, 1 deletion(-)
>>>
>>> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c
>>> b/drivers/vdpa/mlx5/net/mlx5_vnet.c
>>> index ca05f69054b6..0a2b79887085 100644
>>> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
>>> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
>>> @@ -2192,7 +2192,6 @@ static int mlx5_vdpa_reset(struct vdpa_device
>> *vdev)
>>>    	clear_vqs_ready(ndev);
>>>    	mlx5_vdpa_destroy_mr(&ndev->mvdev);
>>>    	ndev->mvdev.status = 0;
>>> -	ndev->mvdev.mlx_features = 0;
>>>    	memset(ndev->event_cbs, 0, sizeof(ndev->event_cbs));
>>>    	ndev->mvdev.actual_features = 0;
>>>    	++mvdev->generation;

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