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Commit 1650b4eb authored by Ignacio Alvarado's avatar Ignacio Alvarado Committed by Radim Krčmář
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KVM: Disable irq while unregistering user notifier 



Function user_notifier_unregister should be called only once for each
registered user notifier.

Function kvm_arch_hardware_disable can be executed from an IPI context
which could cause a race condition with a VCPU returning to user mode
and attempting to unregister the notifier.

Signed-off-by: default avatarIgnacio Alvarado <ikalvarado@google.com>
Cc: stable@vger.kernel.org
Fixes: 18863bdd ("KVM: x86 shared msr infrastructure")
Reviewed-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarRadim Krčmář <rkrcmar@redhat.com>
parent 8b953440

arch/x86/kvm/x86.c

+11 −2
Original line number Diff line number Diff line
@@ -210,7 +210,18 @@ static void kvm_on_user_return(struct user_return_notifier *urn) 
	struct kvm_shared_msrs *locals

		= container_of(urn, struct kvm_shared_msrs, urn);

	struct kvm_shared_msr_values *values;

	unsigned long flags;



	/*

	 * Disabling irqs at this point since the following code could be

	 * interrupted and executed through kvm_arch_hardware_disable()

	 */

	local_irq_save(flags);

	if (locals->registered) {

		locals->registered = false;

		user_return_notifier_unregister(urn);

	}

	local_irq_restore(flags);

	for (slot = 0; slot < shared_msrs_global.nr; ++slot) {

		values = &locals->values[slot];

		if (values->host != values->curr) {
@@ -218,8 +229,6 @@ static void kvm_on_user_return(struct user_return_notifier *urn) 
			values->curr = values->host;

		}

	}

	locals->registered = false;

	user_return_notifier_unregister(urn);

}



static void shared_msr_update(unsigned slot, u32 msr)