Re: [Qemu-devel] [PATCHv2] virtio: verify that all outstanding buffers are flushed

[Paolo Bonzini]

> > We technically should save the addresses and sizes too.  It makes
> > it a heck of a lot safer then re-reading guest memory since we do some
> > validation on the size of the sg elements.
> 
> Not really.
> 
> The guest puts the descriptors in the ring and leaves them there until
> the device acks.  If it changes them once they're exposed but before
> they're acked, it can get either before or after version, and always
> could.

The problems start when the guest tries to race against QEMU and defy
the validation.  Always using the validated version is a bit easier
than redoing the validation after migration.

Paolo