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Commit 42720138 authored Jul 01, 2015 by Radim Krčmář Committed by Paolo Bonzini Jul 03, 2015

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>

parent 2ecd9d29

arch/x86/include/asm/kvm_host.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -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;

arch/x86/kvm/i8254.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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);
		}

arch/x86/kvm/lapic.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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)