Re: [SeaBIOS] [PATCH] kernel/kvm: fix improper nmi emulation

[Avi Kivity]

On 10/10/2011 08:06 AM, Lai Jiangshan wrote:
> From: Kenji Kaneshige
>
> Currently, NMI interrupt is blindly sent to all the vCPUs when NMI
> button event happens. This doesn't properly emulate real hardware on
> which NMI button event triggers LINT1. Because of this, NMI is sent to
> the processor even when LINT1 is maskied in LVT. For example, this
> causes the problem that kdump initiated by NMI sometimes doesn't work
> on KVM, because kdump assumes NMI is masked on CPUs other than CPU0.
>
> With this patch, KVM_NMI ioctl is handled as follows.
>
> When in-kernel irqchip is enabled, KVM_NMI ioctl is handled as a
>  request of triggering LINT1 on the processor. LINT1 is emulated in
>  in-kernel irqchip.
>
> When in-kernel irqchip is disabled, KVM_NMI ioctl is handled as a
>  request of injecting NMI to the processor. This assumes LINT1 is
>  already emulated in userland.

Please add a KVM_NMI section to Documentation/virtual/kvm/api.txt.
> -static int kvm_vcpu_ioctl_nmi(struct kvm_vcpu *vcpu)
> -{
> kvm_inject_nmi(vcpu);
> return 0;
>
> -}
> static int vcpu_ioctl_tpr_access_reporting(struct kvm_vcpu *vcpu,
>   			   struct kvm_tpr_access_ctl *tac)
> {
>
> @@ -3038,9 +3031,10 @@ long kvm_arch_vcpu_ioctl(struct file *fi
>    	break;
>    }
>    case KVM_NMI: {
> r = kvm_vcpu_ioctl_nmi(vcpu);
> if (r)
> 	goto out;
> if (irqchip_in_kernel(vcpu->kvm))
> 	kvm_apic_lint1_deliver(vcpu);
> else
> 	kvm_inject_nmi(vcpu);
> r = 0;
> break;
> }

Why did you drop kvm_vcpu_ioctl_nmi()?

Please add (and document) a KVM_CAP flag that lets userspace know the 
new behaviour is supported.