On Wed, Dec 05, 2012 at 08:38:59PM -0200, Marcelo Tosatti wrote:
> On Wed, Dec 05, 2012 at 01:14:38PM +0200, Gleb Natapov wrote:
> > On Wed, Dec 05, 2012 at 03:43:41AM +0000, Zhang, Yang Z wrote:
> > > >> @@ -5657,12 +5673,20 @@ static int vcpu_enter_guest(struct kvm_vcpu
> > > > *vcpu)
> > > >> }
> > > >>
> > > >> if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) {
> > > >> + /* update archtecture specific hints for APIC
> > > >> + * virtual interrupt delivery */
> > > >> + if (kvm_x86_ops->update_irq)
> > > >> + kvm_x86_ops->update_irq(vcpu);
> > > >> +
> > > >> inject_pending_event(vcpu);
> > > >>
> > > >> /* enable NMI/IRQ window open exits if needed */
> > > >> if (vcpu->arch.nmi_pending)
> > > >> kvm_x86_ops->enable_nmi_window(vcpu);
> > > >> - else if (kvm_cpu_has_interrupt(vcpu) || req_int_win)
> > > >> + else if (kvm_apic_vid_enabled(vcpu)) {
> > > >> + if (kvm_cpu_has_extint(vcpu))
> > > >> + kvm_x86_ops->enable_irq_window(vcpu);
> > > >
> > > > If RVI is non-zero, then interrupt window should not be enabled,
> > > > accordingly to 29.2.2:
> > > >
> > > > "If a virtual interrupt has been recognized (see Section 29.2.1), it will
> > > > be delivered at an instruction boundary when the following conditions all
> > > > hold: (1) RFLAGS.IF = 1; (2) there is no blocking by STI; (3) there is no
> > > > blocking by MOV SS or by POP SS; and (4) the “interrupt-window exiting”
> > > > VM-execution control is 0."
> > > Right. Must check RVI here.
> > >
> > Why? We request interrupt window here because there is ExtINT interrupt
> > pending. ExtINT interrupt has a precedence over APIC interrupts (our
> > current code is incorrect!), so we want vmexit as soon as interrupts are
> > allowed to inject ExtINT and we do not want virtual interrupt to be
> > delivered. I think the (4) there is exactly for this situation.
> >
> > --
> > Gleb.
>
> Right. BTW, delivery of ExtINT has no EOI, so there is no evaluation
> of pending virtual interrupts. Therefore, shouldnt interrupt window be
> enabled when injecting ExtINT so that evaluation of pending virtual
> interrupts is performed on next vm-entry?
>
Good question and I think, luckily for us, the answer is no. Spec uses
two different terms when it talks about virtual interrupts "Evaluation
of Pending Virtual Interrupts" and "Virtual-Interrupt Delivery". As far
as my reading of the spec goes they are not necessary happen at the same
time. So during ExtINT injection "evaluation" will happen (due to vmentry)
and virtual interrupt will be recognized, but not "delivered". It will
be delivered when condition described in section 29.2.2 will be met i.e
when interrupts will be enabled.
Yang, can you confirm this?
--
Gleb.
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