On Fri, 4 Dec 2015 10:06:58 +0800 Jason Wang <jasow...@redhat.com> wrote:
> The problem is for pci: without this patch, guest may always see modern > bar is "disable-modern=false". But with this patch, on an old kernel > that does not support VERSION_1, even "disable-modern=false" were > specified, guest can not see modern bar anymore. Looks like a guest > visible change. But the guest even see a modern bar if the host is not able to present a spec-compliant device? What we have now is a device that looks like a modern device but that does not offer VERSION_1. Probably not spec compliant. If virtio-pci is fixed to not present such broken devices to the guest, this is guest-visible, yes; but only in the sense that the guest will no longer see broken devices, but simply legacy devices if configured.
