On Thu, Apr 14, 2011 at 08:58:41PM +0930, Rusty Russell wrote: > On Tue, 12 Apr 2011 23:01:12 +0300, "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > > On Thu, Mar 10, 2011 at 12:19:42PM +1030, Rusty Russell wrote: > > > Here's an old patch where I played with implementing this: > > > > ... > > > > > > > > virtio: put last_used and last_avail index into ring itself. > > > > > > Generally, the other end of the virtio ring doesn't need to see where > > > you're up to in consuming the ring. However, to completely understand > > > what's going on from the outside, this information must be exposed. > > > For example, if you want to save and restore a virtio_ring, but you're > > > not the consumer because the kernel is using it directly. > > > > > > Fortunately, we have room to expand: > > > > This seems to be true for x86 kvm and lguest but is it true > > for s390? > > Yes, as the ring is page aligned so there's always room. > > > Will this last bit work on s390? > > If I understand correctly the memory is allocated by host there? > > They have to offer the feature, so if the have some way of allocating > non-page-aligned amounts of memory, they'll have to add those extra 2 > bytes. > > So I think it's OK... > Rusty. Correct. I wonder whether we need to pass the relevant flag to vring_size. If we do we'll need to add a new function for that though as vring_size is exported to userspace. -- MST -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
