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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: Ignacio Alvarado <ikalvarado@google.com>
Cc: stable@vger.kernel.org
Fixes: 18863bdd60 ("KVM: x86 shared msr infrastructure")
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
This commit is contained in:
Ignacio Alvarado 2016-11-04 12:15:55 -07:00 committed by Radim Krčmář
parent 8b95344064
commit 1650b4ebc9
1 changed files with 11 additions and 2 deletions
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13
arch/x86/kvm/x86.c
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@ -210,7 +210,18 @@ static void kvm_on_user_return(struct user_return_notifier *urn)
struct kvm_shared_msrs *locals struct kvm_shared_msrs *locals
= container_of(urn, struct kvm_shared_msrs, urn); = container_of(urn, struct kvm_shared_msrs, urn);
struct kvm_shared_msr_values *values; 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) { for (slot = 0; slot < shared_msrs_global.nr; ++slot) {
values = &locals->values[slot]; values = &locals->values[slot];
if (values->host != values->curr) { if (values->host != values->curr) {
@ -218,8 +229,6 @@ static void kvm_on_user_return(struct user_return_notifier *urn)
values->curr = values->host; values->curr = values->host;
} }
} }
locals->registered = false;
user_return_notifier_unregister(urn);
} }
static void shared_msr_update(unsigned slot, u32 msr) static void shared_msr_update(unsigned slot, u32 msr)