Re: [SeaBIOS] [PATCH 1/1 V2] kernel/kvm: fix improper nmi emulation

[Kenji Kaneshige]

(2011/10/12 2:00), 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.
>
> (laijs) Changed from v1:
> Add KVM_NMI API document
> Add KVM_CAP_USER_NMI
>
> Signed-off-by: Kenji Kaneshige
> Tested-by: Lai Jiangshan
>
> Documentation/virtual/kvm/api.txt |   20 ++++++++++++++++++++
>   arch/x86/kvm/irq.h                |    1 +
>   arch/x86/kvm/lapic.c              |    7 +++++++
>   arch/x86/kvm/x86.c                |   12 ++++++++++++
>   include/linux/kvm.h               |    3 +++
>   5 files changed, 43 insertions(+), 0 deletions(-)
>
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index b0e4b9c..5c24cc3 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -1430,6 +1430,26 @@ is supported; 2 if the processor requires all virtual machines to have
>   an RMA, or 1 if the processor can use an RMA but doesn't require it,
>   because it supports the Virtual RMA (VRMA) facility.
>
> +4.64 KVM_NMI
>
> +Capability: KVM_CAP_USER_NMI
> +Architectures: x86
> +Type: vcpu ioctl
> +Parameters: none
> +Returns: 0 on success, -1 on error
>
> +This ioctl injects NMI to the vcpu.
>
> +If with capability KVM_CAP_LAPIC_NMI, 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 lapic 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 lapic.
> The kvm_run structure
>
> Application code obtains a pointer to the kvm_run structure by
>
> 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..6862ef7 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2729,12 +2729,24 @@ static int kvm_vcpu_ioctl_interrupt(struct kvm_vcpu *vcpu,
>    return 0;
>   }
>
> +#ifdef KVM_CAP_LAPIC_NMI
> +static int kvm_vcpu_ioctl_nmi(struct kvm_vcpu *vcpu)
> +{
> if (irqchip_in_kernel(vcpu->kvm))
> kvm_apic_lint1_deliver(vcpu);
> else
> kvm_inject_nmi(vcpu);
> return 0;
>
> +}
> +#else
>   static int kvm_vcpu_ioctl_nmi(struct kvm_vcpu *vcpu)
>   {
>    kvm_inject_nmi(vcpu);
>
> return 0;
>   }
> +#endif

I don't think we need to keep old kvm_vcpu_ioctl_nmi() behavior because
it's clearly a bug.

Regards,
Kenji Kaneshige