Re: [PATCH v2] KVM: x86: avoid redundant REQ_EVENT

Paolo Bonzini
2016-12-14T22:29:39Z

On 14/12/2016 11:59, Denis Plotnikov wrote:
>
> if ((exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT)
> && nested_exit_intr_ack_set(vcpu)) {
> - int irq = kvm_cpu_get_interrupt(vcpu);
> + int irq = kvm_cpu_get_interrupt(vcpu, true);
> WARN_ON(irq < 0);

I think this is not needed, because all nested vmexits end with a KVM_REQ_EVENT:

/*
* the KVM_REQ_EVENT optimization bit is only on for one entry, and if
* we did not inject a still-pending event to L1 now because of
* nested_run_pending, we need to re-enable this bit.
*/
if (vmx->nested.nested_run_pending)
kvm_make_request(KVM_REQ_EVENT, vcpu);

This would allow you to always pass false from kvm_cpu_get_interrupt to
kvm_get_apic_interrupt. Not sure if the additional complication in vmx.c
is worth the simplification in lapic.c. Radim, second opinion? :)

Paolo