On 10/20/2010 05:22 PM, Alex Williamson wrote:
On Wed, 2010-10-20 at 17:17 +0200, Avi Kivity wrote:
> On 10/20/2010 03:43 PM, Michael S. Tsirkin wrote:
> > > >If instead of eventfd we had a file descriptor that can pass vector
> > > >information from vfio to kvm and back, that would fix it,
> > > >as we would not need to set us GSIs at all,
> > > >and not need for userspace to handle MSIX specially.
> > > >
> > >
> > > But if we emulate the entire msix bar in vfio, that's not needed,
right?
> >
> > Yes, I think it is. How does kvm know which interrupt to inject?
> > Either vfio needs to pass that info to qemu and qemu would pass it
> > to kvm, or vfio would have some way to pass that info to kvm
> > directly.
>
> Wait. We can't emulate the BAR in vfio, we have to emulate it in kvm
> where we emulate the write instruction. We then need to tell vfio,
> perhaps via userspace, that masking state has changed.
>
> Seems very intrusive.
We wouldn't direct map the vector table or pending bits, so we could
trap and emulate in qemu, which could then call into reads/writes in
vfio.
That's 100% unintrusive for kvm, but that's what we do today, which is
deemed too slow.
Another option is to fake an interrupt remapping device and do a direct
map. Will those older guests recognize and use it? I imagine not.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
