On 30/06/2015 22:19, Radim Krčmář wrote:
> Writes were a bit racy, but hard to turn into a bug at the same time.
> (Particularly because modern Linux doesn't use this feature anymore.)
I suspect patch 2 makes this race much easier to trigger, so it deserves
Cc: stable@ as well.
Paolo
> Signed-off-by: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> ---
> arch/x86/include/asm/kvm_host.h | 2 +-
> arch/x86/kvm/i8254.c | 2 +-
> arch/x86/kvm/lapic.c | 4 ++--
> 3 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index c7fa57b529d2..2a7f5d782c33 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -607,7 +607,7 @@ struct kvm_arch {
> struct kvm_pic *vpic;
> struct kvm_ioapic *vioapic;
> struct kvm_pit *vpit;
> - int vapics_in_nmi_mode;
> + atomic_t vapics_in_nmi_mode;
> struct mutex apic_map_lock;
> struct kvm_apic_map *apic_map;
>
> diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
> index 4dce6f8b6129..f90952f64e79 100644
> --- a/arch/x86/kvm/i8254.c
> +++ b/arch/x86/kvm/i8254.c
> @@ -305,7 +305,7 @@ static void pit_do_work(struct kthread_work *work)
> * LVT0 to NMI delivery. Other PIC interrupts are just sent to
> * VCPU0, and only if its LVT0 is in EXTINT mode.
> */
> - if (kvm->arch.vapics_in_nmi_mode > 0)
> + if (atomic_read(&kvm->arch.vapics_in_nmi_mode) > 0)
> kvm_for_each_vcpu(i, vcpu, kvm)
> kvm_apic_nmi_wd_deliver(vcpu);
> }
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 8dc32b5a4e0d..954e98a8c2e3 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1264,9 +1264,9 @@ static void apic_manage_nmi_watchdog(struct kvm_lapic *apic, u32 lvt0_val)
> if (lvt0_in_nmi_mode) {
> apic_debug("Receive NMI setting on APIC_LVT0 "
> "for cpu %d\n", apic->vcpu->vcpu_id);
> - apic->vcpu->kvm->arch.vapics_in_nmi_mode++;
> + atomic_inc(&apic->vcpu->kvm->arch.vapics_in_nmi_mode);
> } else
> - apic->vcpu->kvm->arch.vapics_in_nmi_mode--;
> + atomic_dec(&apic->vcpu->kvm->arch.vapics_in_nmi_mode);
> }
> }
>
>
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