This is a note to let you know that I've just added the patch titled
KVM: x86: disable preemption around the call to kvm_arch_vcpu_{un|}blocking
to the 5.18-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-x86-disable-preemption-around-the-call-to-kvm_ar.patch
and it can be found in the queue-5.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 51da2a430f49e1115c2e805118fe91667ced63cf
Author: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
Date: Mon Jun 6 21:08:28 2022 +0300
KVM: x86: disable preemption around the call to kvm_arch_vcpu_{un|}blocking
[ Upstream commit 18869f26df1a11ed11031dfb7392bc7d774062e8 ]
On SVM, if preemption happens right after the call to finish_rcuwait
but before call to kvm_arch_vcpu_unblocking on SVM/AVIC, it itself
will re-enable AVIC, and then we will try to re-enable it again
in kvm_arch_vcpu_unblocking which will lead to a warning
in __avic_vcpu_load.
The same problem can happen if the vCPU is preempted right after the call
to kvm_arch_vcpu_blocking but before the call to prepare_to_rcuwait
and in this case, we will end up with AVIC enabled during sleep -
Ooops.
Signed-off-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
Message-Id: <20220606180829.102503-7-mlevitsk@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 24cb37d19c63..7f1d19689701 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3327,9 +3327,11 @@ bool kvm_vcpu_block(struct kvm_vcpu *vcpu)
vcpu->stat.generic.blocking = 1;
+ preempt_disable();
kvm_arch_vcpu_blocking(vcpu);
-
prepare_to_rcuwait(wait);
+ preempt_enable();
+
for (;;) {
set_current_state(TASK_INTERRUPTIBLE);
@@ -3339,9 +3341,11 @@ bool kvm_vcpu_block(struct kvm_vcpu *vcpu)
waited = true;
schedule();
}
- finish_rcuwait(wait);
+ preempt_disable();
+ finish_rcuwait(wait);
kvm_arch_vcpu_unblocking(vcpu);
+ preempt_enable();
vcpu->stat.generic.blocking = 0;
