On Sun, Dec 11, 2016 at 05:13:45AM +0200, Michael S. Tsirkin wrote: > On Wed, Dec 07, 2016 at 01:52:45PM +0800, Peter Xu wrote: > > Previously vt-d codes only supports 39 bits iova address width. It won't > > be hard to extend it to 48 bits. > > > > After enabling this, we should be able to map larger iova addresses. > > > > To check whether 48 bits aw is enabled, we can grep in the guest dmesg > > with line: "dmar: Host address width 48" (previously it was 39). > > > > Signed-off-by: Peter Xu <pet...@redhat.com> > > I suspect we can't do this for old machine types. > Need to behave in compatible ways.
Sure. I can do that. Btw, is vt-d iommu still in experimental stage? I am just thinking whether it'll be overkill we add lots of tunables before we have one stable and mature vt-d emulation. > Also, is 48 always enough? 5 level with 57 bits > is just around the corner. Please refer to the discussion with Jason - looks like vt-d spec currently supports only 39/48 bits address width? Please correct if I made a mistake. > And is it always supported? for things like vfio > to work, don't we need to check what does host support? Hmm, yes, we should do that. But until now, we still don't have a complete vfio support. IMHO we can postpone this issue until vfio is fully supported. Thanks, -- peterx
