Re: [Qemu-devel] [PATCH 2/2 V2] qemu-kvm: fix improper nmi emulation

[Jan Kiszka]

On 2011-10-11 19:03, 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, inject-nmi request is handled as follows.
> 
> - When in-kernel irqchip is disabled, inject LINT1 instead of NMI
>   interrupt.
> - When in-kernel irqchip is enabled, send nmi event to kernel as the
>   current code does. LINT1 should be emulated in kernel.
> 
> (laijs) changed from v1:
> use KVM_CAP_LAPIC_NMI
> adjust the pic_deliver_nmi() API
> 
> Signed-off-by: Kenji Kaneshige <address@hidden>
> Tested-by: Lai Jiangshan <address@hidden>
> ---
>  hw/apic.c |   26 ++++++++++++++++++++++++++
>  hw/apic.h |    1 +
>  monitor.c |    6 +++++-
>  3 files changed, 32 insertions(+), 1 deletions(-)
> 
> diff --git a/hw/apic.c b/hw/apic.c
> index 69d6ac5..76e8208 100644
> --- a/hw/apic.c
> +++ b/hw/apic.c
> @@ -205,6 +205,32 @@ void apic_deliver_pic_intr(DeviceState *d, int level)
>      }
>  }
>  
> +void apic_deliver_nmi(DeviceState *d)
> +{
> +    APICState *s = DO_UPCAST(APICState, busdev.qdev, d);
> +
> +#ifdef KVM_CAP_LAPIC_NMI

Unneeded #ifdef, x86 has this defined unconditionally.

> +    static int kernel_lapic_nmi;

Some enum with symbolic states would be more readable.

> +
> +    if (kernel_lapic_nmi == 0) {
> +        if (!kvm_enabled() || !kvm_irqchip_in_kernel() ||
> +            !kvm_check_extension(kvm_state, KVM_CAP_LAPIC_NMI)) {

This is wrong: If we run with in-kernel irqchip on an old kernel without
KVM_CAP_LAPIC_NMI, we still must not call into the user space APIC model.

As explained in some other mail, we could then emulate the missing
kernel feature by reading out the current in-kernel APIC state, testing
if LINT1 is unmasked, and then delivering the NMI directly.

Jan

signature.asc
Description: OpenPGP digital signature