Re: [Qemu-devel] [PATCH] kernel/kvm: fix improper nmi emulation

[Jan Kiszka]

On 2011-10-10 08:06, Lai Jiangshan wrote:
> From: Kenji Kaneshige <address@hidden>
> 
> 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.
> 
> Signed-off-by: Kenji Kaneshige <address@hidden>
> Tested-by: Lai Jiangshan <address@hidden>
> ---
>  arch/x86/kvm/irq.h   |    1 +
>  arch/x86/kvm/lapic.c |    8 ++++++++
>  arch/x86/kvm/x86.c   |   14 ++++----------
>  3 files changed, 13 insertions(+), 10 deletions(-)
> 
> Index: linux/arch/x86/kvm/irq.h
> ===================================================================
> --- linux.orig/arch/x86/kvm/irq.h
> +++ linux/arch/x86/kvm/irq.h
> @@ -95,6 +95,7 @@ void kvm_pic_reset(struct kvm_kpic_state
>  void kvm_inject_pending_timer_irqs(struct kvm_vcpu *vcpu);
>  void kvm_inject_apic_timer_irqs(struct kvm_vcpu *vcpu);
>  void kvm_apic_nmi_wd_deliver(struct kvm_vcpu *vcpu);
> +void kvm_apic_lint1_deliver(struct kvm_vcpu *vcpu);
>  void __kvm_migrate_apic_timer(struct kvm_vcpu *vcpu);
>  void __kvm_migrate_pit_timer(struct kvm_vcpu *vcpu);
>  void __kvm_migrate_timers(struct kvm_vcpu *vcpu);
> Index: linux/arch/x86/kvm/lapic.c
> ===================================================================
> --- linux.orig/arch/x86/kvm/lapic.c
> +++ linux/arch/x86/kvm/lapic.c
> @@ -1039,6 +1039,14 @@ void kvm_apic_nmi_wd_deliver(struct kvm_
>               kvm_apic_local_deliver(apic, APIC_LVT0);
>  }
>  
> +void kvm_apic_lint1_deliver(struct kvm_vcpu *vcpu)
> +{
> +     struct kvm_lapic *apic = vcpu->arch.apic;
> +
> +     if (apic)

WARN_ON(!apic)? Looks like that case would be a kernel bug.

> +             kvm_apic_local_deliver(apic, APIC_LVT1);
> +}
> +
>  static struct kvm_timer_ops lapic_timer_ops = {
>       .is_periodic = lapic_is_periodic,
>  };
> Index: linux/arch/x86/kvm/x86.c
> ===================================================================
> --- linux.orig/arch/x86/kvm/x86.c
> +++ linux/arch/x86/kvm/x86.c
> @@ -2729,13 +2729,6 @@ static int kvm_vcpu_ioctl_interrupt(stru
>       return 0;
>  }
>  
> -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;
>       }

Looks OK otherwise.

Jan

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