Re: [Qemu-devel] [PATCH 1/1 V5 tuning] kernel/kvm: introduce KVM_SET_LINT1 and fix improper nmi emulation

[Sasha Levin]

On Fri, 2011-10-14 at 17:51 +0800, Lai Jiangshan wrote:
> 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 masked 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, we introduce introduce KVM_SET_LINT1,
> and we can use KVM_SET_LINT1 to correctly emulate NMI button
> without change the old KVM_NMI behavior.
> 
> Signed-off-by: Lai Jiangshan <address@hidden>
> Reported-by: Kenji Kaneshige <address@hidden>
> ---

It could use a documentation update as well.

>  arch/x86/kvm/irq.h   |    1 +
>  arch/x86/kvm/lapic.c |    7 +++++++
>  arch/x86/kvm/x86.c   |    8 ++++++++
>  include/linux/kvm.h  |    3 +++
>  4 files changed, 19 insertions(+), 0 deletions(-)
> diff --git a/arch/x86/kvm/irq.h b/arch/x86/kvm/irq.h
> index 53e2d08..0c96315 100644
> --- a/arch/x86/kvm/irq.h
> +++ b/arch/x86/kvm/irq.h
> @@ -95,6 +95,7 @@ void kvm_pic_reset(struct kvm_kpic_state *s);
>  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);
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 57dcbd4..87fe36a 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1039,6 +1039,13 @@ void kvm_apic_nmi_wd_deliver(struct kvm_vcpu *vcpu)
>               kvm_apic_local_deliver(apic, APIC_LVT0);
>  }
>  
> +void kvm_apic_lint1_deliver(struct kvm_vcpu *vcpu)
> +{
> +     struct kvm_lapic *apic = vcpu->arch.apic;
> +
> +     kvm_apic_local_deliver(apic, APIC_LVT1);
> +}
> +
>  static struct kvm_timer_ops lapic_timer_ops = {
>       .is_periodic = lapic_is_periodic,
>  };
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 84a28ea..fccd094 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2077,6 +2077,7 @@ int kvm_dev_ioctl_check_extension(long ext)
>       case KVM_CAP_XSAVE:
>       case KVM_CAP_ASYNC_PF:
>       case KVM_CAP_GET_TSC_KHZ:
> +     case KVM_CAP_SET_LINT1:
>               r = 1;
>               break;
>       case KVM_CAP_COALESCED_MMIO:
> @@ -3264,6 +3265,13 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
>  
>               goto out;
>       }
> +     case KVM_SET_LINT1: {
> +             r = -EINVAL;
> +             if (!irqchip_in_kernel(vcpu->kvm))
> +                     goto out;
> +             r = 0;
> +             kvm_apic_lint1_deliver(vcpu);

We simply ignore the return value of kvm_apic_local_deliver() and assume
it always works. why?


-- 

Sasha.