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

[Jan Kiszka <jan.kiszka@web.de>]

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On 2011-10-14 11:03, 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 <laijs@cn.fujitsu.com>
> Reported-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
> ---
>  arch/x86/include/asm/kvm.h |    1 +
>  arch/x86/kvm/irq.h         |    1 +
>  arch/x86/kvm/lapic.c       |    7 +++++++
>  arch/x86/kvm/x86.c         |    8 ++++++++
>  include/linux/kvm.h        |    5 +++++
>  5 files changed, 22 insertions(+), 0 deletions(-)
> diff --git a/arch/x86/include/asm/kvm.h b/arch/x86/include/asm/kvm.h
> index 4d8dcbd..88d0ac3 100644
> --- a/arch/x86/include/asm/kvm.h
> +++ b/arch/x86/include/asm/kvm.h
> @@ -24,6 +24,7 @@
>  #define __KVM_HAVE_DEBUGREGS
>  #define __KVM_HAVE_XSAVE
>  #define __KVM_HAVE_XCRS
> +#define __KVM_HAVE_SET_LINT1
>  
>  /* Architectural interrupt line count. */
>  #define KVM_NR_INTERRUPTS 256
> 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);
> +	}
>  	default:
>  		r = -EINVAL;
>  	}
> diff --git a/include/linux/kvm.h b/include/linux/kvm.h
> index aace6b8..3a10572 100644
> --- a/include/linux/kvm.h
> +++ b/include/linux/kvm.h
> @@ -554,6 +554,9 @@ struct kvm_ppc_pvinfo {
>  #define KVM_CAP_PPC_SMT 64
>  #define KVM_CAP_PPC_RMA	65
>  #define KVM_CAP_S390_GMAP 71
> +#ifdef __KVM_HAVE_SET_LINT1
> +#define KVM_CAP_SET_LINT1 72
> +#endif

Actually, there is no need for __KVM_HAVE_SET_LINT1 and #ifdef. User
land will just do a runtime check.

Jan


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