Re: [PATCH] vdpa/mlx5: set_features should allow reset to zero

[Jason Wang]

On 2021/3/1 5:30 上午, Michael S. Tsirkin wrote:
> 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?


I meant the workaround that is done by 452639a64ad8 ("vdpa: make sure 
set_features is invoked for legacy").

Thanks


>