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KVM: x86: make vapics_in_nmi_mode atomic 

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.)

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
[Actually the next patch makes it much, much easier to trigger the race
 so I'm including this one for stable@ as well. - Paolo]
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Radim Krčmář 2015-07-01 15:31:49 +02:00 committed by Paolo Bonzini
parent 2ecd9d29ab
commit 42720138b0
3 changed files with 4 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/x86/include/asm/kvm_host.h
View File

@ -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;

2
arch/x86/kvm/i8254.c
View File

@ -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);
}

4
arch/x86/kvm/lapic.c
View File

@ -1263,10 +1263,10 @@ static void apic_manage_nmi_watchdog(struct kvm_lapic *apic, u32 lvt0_val)
if (!nmi_wd_enabled) {
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 if (nmi_wd_enabled)
apic->vcpu->kvm->arch.vapics_in_nmi_mode--;
atomic_dec(&apic->vcpu->kvm->arch.vapics_in_nmi_mode);
}
static int apic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)