On Mon, May 18, 2009 at 12:00:40PM +0300, Avi Kivity wrote:
> Gleb Natapov wrote:
>> @@ -3174,10 +3174,11 @@ static void inject_pending_irq(struct kvm_vcpu
>> *vcpu, struct kvm_run *kvm_run)
>> vcpu->arch.nmi_injected = true;
>> kvm_x86_ops->set_nmi(vcpu);
>> }
>> - } else if (kvm_cpu_has_interrupt(vcpu)) {
>> - if (kvm_x86_ops->interrupt_allowed(vcpu)) {
>> - kvm_queue_interrupt(vcpu, kvm_cpu_get_interrupt(vcpu),
>> - false);
>> + } else if (kvm_x86_ops->interrupt_allowed(vcpu)) {
>> + int vec = kvm_cpu_get_interrupt(vcpu);
>> + if (vec != -1) {
>> + printk(KERN_ERR"inject %d rip=%x\n", vec,
>> kvm_rip_read(vcpu));
>> + kvm_queue_interrupt(vcpu, vec, false);
>> kvm_x86_ops->set_irq(vcpu);
>> } }
>>
>
> Not sure if this is a win. Usually interrupts are allowed, so we'll
> have to do both calculations. On vmx ->interrupt_allowed() reads the
> vmcs, which is slow.
>
Depend on how slow vmcs read is. In case when interrupt is available we
also scan IRR twice with current code: first time in kvm_cpu_has_interrupt()
and another in kvm_cpu_get_interrupt().
If we want to optimize vmcs access, and for nested virtualization we may
want to do it, we can read common ones on exit and use in memory copy.
--
Gleb.
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