This is a note to let you know that I've just added the patch titled
KVM: Disable irq while unregistering user notifier
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-disable-irq-while-unregistering-user-notifier.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 1650b4ebc99da4c137bfbfc531be4a2405f951dd Mon Sep 17 00:00:00 2001
From: Ignacio Alvarado <ikalvarado@xxxxxxxxxx>
Date: Fri, 4 Nov 2016 12:15:55 -0700
Subject: KVM: Disable irq while unregistering user notifier
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From: Ignacio Alvarado <ikalvarado@xxxxxxxxxx>
commit 1650b4ebc99da4c137bfbfc531be4a2405f951dd upstream.
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@xxxxxxxxxx>
Fixes: 18863bdd60f8 ("KVM: x86 shared msr infrastructure")
Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Radim Krčmář <rkrcmar@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/x86.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -199,7 +199,18 @@ static void kvm_on_user_return(struct us
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) {
@@ -207,8 +218,6 @@ static void kvm_on_user_return(struct us
values->curr = values->host;
}
}
- locals->registered = false;
- user_return_notifier_unregister(urn);
}
static void shared_msr_update(unsigned slot, u32 msr)
Patches currently in stable-queue which might be from ikalvarado@xxxxxxxxxx are
queue-4.4/kvm-disable-irq-while-unregistering-user-notifier.patch
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