On Wed, Jul 28, 2010 at 07:31:03PM +0300, Avi Kivity wrote:
> On 07/28/2010 07:21 PM, Marcelo Tosatti wrote:
> >On Tue, Jul 27, 2010 at 04:19:35PM +0300, Avi Kivity wrote:
> >>Instead of blindly attempting to inject an event before each guest entry,
> >>check for a possible event first in vcpu->requests. Sites that can trigger
> >>event injection are modified to set KVM_REQ_EVENT:
> >>
> >>- interrupt, nmi window opening
> >>- ppr updates
> >>- i8259 output changes
> >>- local apic irr changes
> >>- rflags updates
> >>- gif flag set
> >>- event set on exit
> >>
> >>This improves non-injecting entry performance, and sets the stage for
> >>non-atomic injection.
> >>
> >>Signed-off-by: Avi Kivity<avi@xxxxxxxxxx>
> >>---
> >> arch/x86/kvm/i8259.c | 1 +
> >> arch/x86/kvm/lapic.c | 12 ++++++++++--
> >> arch/x86/kvm/svm.c | 8 +++++++-
> >> arch/x86/kvm/vmx.c | 6 ++++++
> >> arch/x86/kvm/x86.c | 35 ++++++++++++++++++++++++++---------
> >> include/linux/kvm_host.h | 1 +
> >> 6 files changed, 51 insertions(+), 12 deletions(-)
> >>
> >>@@ -4731,17 +4737,19 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> >> goto out;
> >> }
> >>
> >>- inject_pending_event(vcpu);
> >>+ if (kvm_check_request(KVM_REQ_EVENT, 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)
> >>- kvm_x86_ops->enable_irq_window(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)
> >>+ kvm_x86_ops->enable_irq_window(vcpu);
> >Problem is it might not be possible to inject the event signalled by
> >KVM_REQ_EVENT, say an interrupt from an irqchip, if there is an event
> >that needs reinjection (or an exception).
>
> That can happen event now, no? A pending exception, interrupt comes
> along, injection picks up the exception but leaves the interrupt.
>
> Now the situation can be more complicated:
>
> - pending exception
> - injection
> - interrupt, sets KVM_REQ_EVENT
> - notices KVM_REQ_EVENT
> - drops KVM_REQ_EVENT, cancels exception (made pending again)
> - goes back
> - injection (injects exception again, interrupt is pending)
>
> as far as I can tell, this is all fine.
But you cleared KVM_REQ_EVENT. Which means you're not going to inject
the pending interrupt on the next entry.
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