Re: [PATCH] KVM: Improvements for task switching

[Jan Kiszka <jan.kiszka@siemens.com>]

Jan Kiszka wrote:
> Bernhard Kohl wrote:
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index 5cf28df..eca57a3 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -3357,7 +3357,8 @@ static void vmx_intr_assist(struct kvm_vcpu *vcpu)
>>  			enable_irq_window(vcpu);
>>  	}
>>  	if (vcpu->arch.interrupt.pending) {
>> -		vmx_inject_irq(vcpu, vcpu->arch.interrupt.nr);
>> +		if (vcpu->arch.interrupt_window_open)
>> +			vmx_inject_irq(vcpu, vcpu->arch.interrupt.nr);
>>  		if (kvm_cpu_has_interrupt(vcpu))
>>  			enable_irq_window(vcpu);
>>  	}
> 
> That causes concerns on my side as we had a hard time stabilizing this
> code. Need to think about it. Do you happen to have a test case for this
> (if it's not publicly shareable, contact me directly)? Did you check
> that this change causes no obvious regressions to other guests? What
> about the user-inject IRQ case, does it already work for you as-is?

Hmm, do_interrupt_requests will most likely not cause troubles as it
both pends and injects interrupts only when the window if open. I don't
get the scenario behind this here yet, but I think it would be a very
good chance to align the code layout of vmx_intr_assist to
do_interrupt_requests in this respect, either finally de-optimizing or
even breaking both :) - or bringing them in the same correct form.

Jan

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