On 29/06/20 15:46, Vitaly Kuznetsov wrote: >> + if (!lapic_in_kernel(vcpu)) >> + return 1; >> + > I'm not sure how much we care about !lapic_in_kernel() case but this > change should be accompanied with userspace changes to not expose > KVM_FEATURE_ASYNC_PF_INT or how would the guest know that writing a > legitimate value will result in #GP? Almost any pv feature is broken with QEMU if kernel_irqchip=off. I wouldn't bother and I am seriously thinking of dropping all support for that, including: - just injecting #UD for MOV from/to CR8 unless lapic_in_kernel() - make KVM_INTERRUPT fail unless irqchip_in_kernel(), so that KVM_INTERRUPT is only used to inject EXTINT with kernel_irqchip=split Paolo > Alternatively, we may just return '0' here: guest will be able to check > what's in the MSR to see if the feature was enabled. Normally, guests > shouldn't care about this but maybe there are cases when they do? >
