On Wed, 2008-11-12 at 22:51 +1030, Rusty Russell wrote: > On Tuesday 11 November 2008 10:07:09 Hollis Blanchard wrote: > > Both sides of the virtio interface must agree about how big a pfn really > > is. This is particularly an issue on architectures where the page size is > > configurable (e.g. PowerPC, IA64) -- the interface must be independent of > > PAGE_SHIFT. > > > > Currently there are three distinct problems: > > * The shift count used when passing the physical address of the ring to a > > PCI-based back end. > > * The ring layout itself is padded to span at least two "pages". > > * The balloon driver operates in units of "pages". > > Hi Hollis, > > The more I thought about this, the more I think we're not solving this > as neatly as we could. The trigger was noting that we're breaking the > userspace API (vring_size and vring_init are exposed to userspace): I > know that qemu cut & pastes, but that's no excuse. > > So instead, I've introduced separate constants for each use. Yes, > all these constants are 12/4096. But just to be contrary, at the end > is a patch to change lguest to 128. And there's no reason this > couldn't change in future using some guest detection scheme. OK. I thought it was simpler to just say "4KB everywhere" in all aspects of the virtio interface, but I'm happy as long as we solve the problem somehow. :) -- Hollis Blanchard IBM Linux Technology Center -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
