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

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:

quoted

On 2021/2/24 4:43 下午, Michael S. Tsirkin wrote:

quoted

On Wed, Feb 24, 2021 at 04:26:43PM +0800, Jason Wang wrote:

quoted

      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