linux-kernel - Re: [PATCH 6/6] kvm: x86: do not use KVM_REQ

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Date:   Wed, 8 Feb 2017 17:23:18 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Radim Krčmář <rkrcmar@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        "Wu, Feng" <feng.wu@...el.com>
Subject: Re: [PATCH 6/6] kvm: x86: do not use KVM_REQ_EVENT for APICv
 interrupt injection



On 07/02/2017 20:58, Radim Krčmář wrote:
>> -	local_irq_disable();
>> +	if (kvm_lapic_enabled(vcpu)) {
>> +		/*
>> +		 * This handles the case where a posted interrupt was
>> +		 * notified with kvm_vcpu_kick.
>> +		 */
>> +		if (kvm_x86_ops->sync_pir_to_irr)
>> +			kvm_x86_ops->sync_pir_to_irr(vcpu);
> Hm, this is not working well when nesting while L1 has assigned devices:
> if the posted interrupt arrives just before local_irq_disable(), then
> we'll just enter L2 instead of doing a nested VM exit (in case we have
> interrupt exiting).
> 
> And after reading the code a bit, I think we allow posted interrupts in
> L2 while L1 has assigned devices that use posted interrupts, and that it
> doesn't work.

So you mean the interrupt is delivered to L2?  The fix would be to wrap
L2 entry and exit with some subset of pi_pre_block/pi_post_block.

Paolo