Re: [PATCH] vhost: accept VIRTIO_F_ORDER_PLATFORM as a valid SVQ feature

[Michael S. Tsirkin]

On Thu, Mar 02, 2023 at 12:30:52PM +0100, Eugenio Perez Martin wrote:
> > You need to pass this to guest. My point is that there is no reason to
> > get it from the kernel driver. QEMU can figure out whether the flag is
> > needed itself.
> >
> 
> Ok, I can see now how the HW device does not have all the knowledge to
> offer this flag or not. But I'm not sure how qemu can know either.
> 
> If qemu opens /dev/vhost-vdpa-N, how can it know it? It has no way to
> tell if the device is sw or hw as far as I know. Am I missing
> something?
> 
> Thanks!

This is what I said earlier.  You can safely assume vdpa needs this
flag. Only exception is vduse and we don't care about performance there.

-- 
MST