[PATCH 2/3] KVM: SVM: Unregister KVM's GALog notifier on kvm-amd.ko exit

[Sean Christopherson <seanjc@google.com>]

Unregister the GALog notifier (used to get notified of wake events for
blocking vCPUs) on kvm-amd.ko exit so that a KVM or IOMMU driver bug that
results in a spurious GALog event "only" results in a spurious IRQ, and
doesn't trigger a use-after-free due to executing unloaded module code.

Fixes: 5881f73757cc ("svm: Introduce AMD IOMMU avic_ga_log_notifier")
Reported-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
Closes: https://lore.kernel.org/all/20250918130320.GA119526@k08j02272.eu95sqa
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/svm/avic.c | 6 ++++++
 arch/x86/kvm/svm/svm.c  | 2 ++
 arch/x86/kvm/svm/svm.h  | 1 +
 3 files changed, 9 insertions(+)

diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index f286b5706d7c..3ab74f2bd584 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -1243,3 +1243,9 @@ bool __init avic_hardware_setup(void)
 
 	return true;
 }
+
+void avic_hardware_unsetup(void)
+{
+	if (avic)
+		amd_iommu_register_ga_log_notifier(NULL);
+}
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index efc3a7adebef..76055c0ba177 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -921,6 +921,8 @@ static void svm_hardware_unsetup(void)
 {
 	int cpu;
 
+	avic_hardware_unsetup();
+
 	sev_hardware_unsetup();
 
 	for_each_possible_cpu(cpu)
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index e4b04f435b3d..b0fe40c21728 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -805,6 +805,7 @@ extern struct kvm_x86_nested_ops svm_nested_ops;
 )
 
 bool __init avic_hardware_setup(void);
+void avic_hardware_unsetup(void);
 int avic_ga_log_notifier(u32 ga_tag);
 void avic_vm_destroy(struct kvm *kvm);
 int avic_vm_init(struct kvm *kvm);
-- 
2.51.0.858.gf9c4a03a3a-goog