Re: [PATCH 5/6] vdpa: add get_vq_num_unchangeable callback in vdpa_config_ops

[Michael S. Tsirkin]

On Thu, Sep 09, 2021 at 10:55:03AM +0800, Jason Wang wrote:
> On Wed, Sep 8, 2021 at 8:23 PM Wu Zongyong <wuzongyong@xxxxxxxxxxxxxxxxx> wrote:
> >
> > This new callback is used to indicate whether the vring size can be
> > change or not. It is useful when we have a legacy virtio pci device as
> > the vdpa device for there is no way to negotiate the vring num by the
> > specification.
> 
> So I'm not sure it's worth bothering. E.g what if we just fail
> VHOST_SET_VRING_NUM it the value doesn't match what hardware has?
> 
> Thanks

More importantly is there and actual plan for supporting
legacy devices? I don't think they currently work at a number
of levels.

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MST