Re: [PATCH 2/2] KVM: x86: Fix split-irqchip vs interrupt injection window request

Paolo Bonzini <pbonzini@xxxxxxxxxx> · Thu, 15 Apr 2021 08:07:06 +0200

On 15/04/21 02:59, Lai Jiangshan wrote:
The next call to inject_pending_event() will reach here AT FIRST with
vcpu->arch.exception.injected==false and vcpu->arch.exception.pending==false

          ... if (!vcpu->arch.exception.pending) {
                  if (vcpu->arch.nmi_injected) {
                          static_call(kvm_x86_set_nmi)(vcpu);
                          can_inject = false;
                  } else if (vcpu->arch.interrupt.injected) {
                          static_call(kvm_x86_set_irq)(vcpu);
                          can_inject = false;

And comes here and vcpu->arch.interrupt.injected is true for there is
an interrupt queued by KVM_INTERRUPT for pure user irqchip. It then does
the injection of the interrupt without checking the EFLAGS.IF.

Ok, understood now.  Yeah, that could be a problem for userspace irqchip 
so we should switch it to use pending_external_vector instead.  Are you 
going to write the patch or should I?

Thanks!

Paolo

My question is that what stops the next call to inject_pending_event()
to reach here when KVM_INTERRUPT is called with exepction pending.