On Thu, Feb 03, 2011 at 10:32:25AM +0100, Jan Kiszka wrote: > On 2011-02-03 09:18, Avi Kivity wrote: > > On 02/02/2011 05:52 PM, Jan Kiszka wrote: > >>>> > >>> If there is no problem in the logic of this commit (and I do not see > >>> one yet) then we somewhere miss kicking vcpu when interrupt, that should > >>> be > >>> handled, arrives? > >> > >> I'm not yet confident about the logic of the kernel patch: mov to cr8 is > >> serializing. If the guest raises the tpr and then signals this with a > >> succeeding, non vm-exiting instruction to the other vcpus, one of those > >> could inject an interrupt with a higher priority than the previous tpr, > >> but a lower one than current tpr. QEMU user space would accept this > >> interrupt - and would likely surprise the guest. Do I miss something? > > > > apic_get_interrupt() is only called from the vcpu thread, so it should > > see a correct tpr. > > > > The only difference I can see with the patch is that we may issue a > > spurious cpu_interrupt(). But that shouldn't do anything bad, should it? > > I tested this yesterday, and it doesn't confuse Windows. It actually > receives quite a few spurious IRQs in normal operation, w/ or w/o the > kernel's tpr optimization.
http://www.mail-archive.com/kvm@vger.kernel.org/msg41681.html tpr of a vcpu should always be inspected in vcpu context, instead of iothread context?
