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Date:   Sun, 28 Feb 2021 16:30:08 -0500
From:   "Michael S. Tsirkin" <mst@redhat.com>
To:     Jason Wang <jasowang@redhat.com>
Cc:     Si-Wei Liu <si-wei.liu@oracle.com>, elic@nvidia.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
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On Wed, Feb 24, 2021 at 05:30:37PM +0800, Jason Wang wrote:
> 
> On 2021/2/24 4:43 下午, Michael S. Tsirkin wrote:
> > On Wed, Feb 24, 2021 at 04:26:43PM +0800, Jason Wang wrote:
> > >      Basically on first guest access QEMU would tell kernel whether
> > >      guest is using the legacy or the modern interface.
> > >      E.g. virtio_pci_config_read/virtio_pci_config_write will call ioctl(ENABLE_LEGACY, 1)
> > >      while virtio_pci_common_read will call ioctl(ENABLE_LEGACY, 0)
> > > 
> > > 
> > > But this trick work only for PCI I think?
> > > 
> > > Thanks
> > ccw has a revision it can check. mmio does not have transitional devices
> > at all.
> 
> 
> Ok, then we can do the workaround in the qemu, isn't it?
> 
> Thanks

which one do you mean?

-- 
MST