On Wed, 2010-10-20 at 17:26 +0200, Avi Kivity wrote: > 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. Nope, I think it's a non-starter to think anything but the latest current guests will have support for that. Alex -- 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
