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. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux
