This is a note to let you know that I've just added the patch titled
KVM: fix avic_set_running for preemptable kernels
to the 5.15-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-fix-avic_set_running-for-preemptable-kernels.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 7cfc5c653b07782e7059527df8dc1e3143a7591e Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Date: Tue, 30 Nov 2021 03:46:07 -0500
Subject: KVM: fix avic_set_running for preemptable kernels
From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
commit 7cfc5c653b07782e7059527df8dc1e3143a7591e upstream.
avic_set_running() passes the current CPU to avic_vcpu_load(), albeit
via vcpu->cpu rather than smp_processor_id(). If the thread is migrated
while avic_set_running runs, the call to avic_vcpu_load() can use a stale
value for the processor id. Avoid this by blocking preemption over the
entire execution of avic_set_running().
Reported-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Fixes: 8221c1370056 ("svm: Manage vcpu load/unload when enable AVIC")
Cc: stable@xxxxxxxxxxxxxxx
Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/svm/avic.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -988,16 +988,18 @@ void avic_vcpu_put(struct kvm_vcpu *vcpu
static void avic_set_running(struct kvm_vcpu *vcpu, bool is_run)
{
struct vcpu_svm *svm = to_svm(vcpu);
+ int cpu = get_cpu();
+ WARN_ON(cpu != vcpu->cpu);
svm->avic_is_running = is_run;
- if (!kvm_vcpu_apicv_active(vcpu))
- return;
-
- if (is_run)
- avic_vcpu_load(vcpu, vcpu->cpu);
- else
- avic_vcpu_put(vcpu);
+ if (kvm_vcpu_apicv_active(vcpu)) {
+ if (is_run)
+ avic_vcpu_load(vcpu, cpu);
+ else
+ avic_vcpu_put(vcpu);
+ }
+ put_cpu();
}
void svm_vcpu_blocking(struct kvm_vcpu *vcpu)
Patches currently in stable-queue which might be from pbonzini@xxxxxxxxxx are
queue-5.15/kvm-disallow-user-memslot-with-size-that-exceeds-unsigned-long.patch
queue-5.15/kvm-fix-avic_set_running-for-preemptable-kernels.patch
