On Thu, Oct 11, 2012 at 03:44:10PM +0200, Avi Kivity wrote: > On 10/11/2012 03:44 PM, Michael S. Tsirkin wrote: > > On Thu, Oct 11, 2012 at 03:34:54PM +0200, Avi Kivity wrote: > >> On 10/11/2012 03:31 PM, Michael S. Tsirkin wrote: > >> > On Thu, Oct 11, 2012 at 03:27:03PM +0200, Avi Kivity wrote: > >> >> vhost doesn't support guest iommus yet, indicate it to the user > >> >> by gently depositing a core on their disk. > >> >> > >> >> Signed-off-by: Avi Kivity <a...@redhat.com> > >> > > >> > Actually there is no problem. virtio bypasses an IOMMU, > >> > so vhost works fine by writing into guest memory directly. > >> > > >> > So I don't think we need this patch. > >> > >> The pci subsystem should set up the iommu so that it ignores virtio > >> devices. If it does, an emulated iommu will not reach vhost. If it > >> doesn't, then it will, and the assert() will alert us that we have a bug. > > > > You mean pci subsystem in the guest? I'm pretty sure that's not > > the case at the moment: iommu is on by default and applies > > to all devices unless you do something special. > > I see where you are coming from but it does > > not look right to break all existing guests. > > No, qemu should configure virtio devices to bypass the iommu, even if it > is on.
Okay so there will be some API that virtio devices should call to achieve this? > > Also - I see no reason to single out vhost - I think same applies with > > any virtio device, since it doesn't use the DMA API. > > True. > > -- > error compiling committee.c: too many arguments to function