On 2011-02-03 11:04, Marcelo Tosatti wrote: > 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@xxxxxxxxxxxxxxx/msg41681.html Don't get the scenario yet: We do not inject (or set isr) over the context of apic_set_irq caller. > > tpr of a vcpu should always be inspected in vcpu context, instead of > iothread context? Maybe this is true for the in-kernel model, but I don't see the issue (anymore) for the way user space works. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux -- 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
