Please next time mention mainstream commit like:
ms commit: 1650b4e ("KVM: Disable irq while unregistering user notifier")
Thank you.
--
Best regards,
Konstantin Khorenko,
Virtuozzo Linux Kernel Team
On 11/22/2016 12:09 PM, Evgeny Yakovlev wrote:
From: Ignacio Alvarado <ikalvar...@google.com>
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 <ikalvar...@google.com>
Reviewed-by: Paolo Bonzini <pbonz...@redhat.com>
Backport of https://patchwork.kernel.org/patch/9413131/
Fixes https://jira.sw.ru/browse/PSBM-55099
Signed-off-by: Evgeny Yakovlev <eyakov...@virtuozzo.com>
---
arch/x86/kvm/x86.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ea058a2..4b2754b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -198,7 +198,18 @@ 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) {
@@ -206,8 +217,6 @@ 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)
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