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From: "Michael S. Tsirkin" <mst@redhat.com>
To: Jason Wang <jasowang@redhat.com>
Cc: Eli Cohen <elic@nvidia.com>, Si-Wei Liu <si-wei.liu@oracle.com>,
	linux-kernel@vger.kernel.org,
	virtualization@lists.linux-foundation.org,
	netdev@vger.kernel.org
Subject: Re: [PATCH] vdpa/mlx5: set_features should allow reset to zero
Date: Tue, 23 Feb 2021 04:55:37 -0500
Message-ID: <20210223045519-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <65494f6b-9613-1c0e-4a36-e4af2965235e@redhat.com>

On Tue, Feb 23, 2021 at 05:48:10PM +0800, Jason Wang wrote:
> 
> 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
> 

That is why I asked whether Eli meant catch.

-- 
MST


  reply index

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-19 11:54 Si-Wei Liu
2021-02-21 14:44 ` Eli Cohen
2021-02-21 21:52   ` Michael S. Tsirkin
2021-02-22  6:05     ` Eli Cohen
2021-02-23  9:26       ` Michael S. Tsirkin
2021-02-23  9:48         ` Jason Wang
2021-02-23  9:55           ` Michael S. Tsirkin [this message]
2021-02-22  4:14 ` Jason Wang
2021-02-22  7:34   ` Michael S. Tsirkin
2021-02-23  1:12     ` Si-Wei Liu
2021-02-23  2:03       ` Jason Wang
2021-02-23 13:26         ` Michael S. Tsirkin
2021-02-23 19:35           ` Si-Wei Liu
2021-02-24  3:20             ` Jason Wang
2021-02-24  5:17               ` Michael S. Tsirkin
2021-02-24  6:02                 ` Jason Wang
2021-02-24  6:45                 ` Eli Cohen
2021-02-24  6:47                   ` Michael S. Tsirkin
2021-02-24  6:55                     ` Jason Wang
2021-02-24  7:12                       ` Michael S. Tsirkin
2021-02-24 12:40                         ` Eli Cohen
2021-02-24  7:17                       ` Eli Cohen
2021-02-24  5:04             ` Michael S. Tsirkin
2021-02-24  6:04               ` Jason Wang
2021-02-24  6:46                 ` Michael S. Tsirkin
2021-02-24  6:53                   ` Jason Wang
2021-02-24  7:17                     ` Michael S. Tsirkin
     [not found]                       ` <babc654d-8dcd-d8a2-c3b6-d20cc4fc554c@redhat.com>
2021-02-24  8:43                         ` Michael S. Tsirkin
2021-02-24  9:30                           ` Jason Wang
2021-02-28 21:30                             ` Michael S. Tsirkin
2021-03-01  3:53                               ` Jason Wang
2021-02-24 18:24               ` Si-Wei Liu
2021-02-26  0:56                 ` Si-Wei Liu
2021-02-28 21:27                   ` Michael S. Tsirkin
2021-03-01 18:08                     ` Si-Wei Liu
2021-02-28 21:28                 ` Michael S. Tsirkin
2021-02-28 21:34                 ` Michael S. Tsirkin
2021-03-01  3:56                   ` Jason Wang
2021-03-02  9:47                     ` Michael S. Tsirkin
2021-03-02 10:53                       ` Jason Wang
2021-02-22 17:09   ` Si-Wei Liu
2021-02-23  2:03     ` Jason Wang
2021-02-23  9:25     ` Michael S. Tsirkin
2021-02-23  9:46       ` Jason Wang
2021-02-23 10:01         ` Michael S. Tsirkin
2021-02-23 10:17           ` Jason Wang
2021-02-24  9:40             ` Jason Wang
2021-02-23 10:04         ` [virtio-dev] " Cornelia Huck
2021-02-23 10:31           ` Jason Wang
2021-02-23 10:58             ` Cornelia Huck
2021-02-24  9:29               ` Jason Wang
2021-02-24 11:12                 ` Cornelia Huck
2021-02-25  4:36                   ` Jason Wang
2021-02-25 13:26                     ` Cornelia Huck
2021-02-25 18:53                     ` Michael S. Tsirkin
2021-02-26  8:19                       ` Jason Wang
2021-02-28 21:25                         ` Michael S. Tsirkin
2021-03-01  3:51                           ` Jason Wang
2021-03-02 12:08                             ` Cornelia Huck
     [not found]                               ` <5f6972fe-7246-b622-958d-9cab8dd98e21@redhat.com>
2021-03-03  8:29                                 ` Cornelia Huck
2021-03-04  8:24                                   ` Jason Wang
2021-03-04 13:50                                     ` Cornelia Huck
2021-03-05  3:01                                       ` Jason Wang
2021-02-23 12:26 ` Michael S. Tsirkin

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