[PATCH 2/2] KVM: x86: flush pending lapic jump label updates on module unload

[David Matlack <dmatlack@google.com>]

KVM's lapic emulation uses static_key_deferred (apic_{hw,sw}_disabled).
These are implemented with delayed_work structs which can still be
pending when the KVM module is unloaded. We've seen this cause kernel
panics when the kvm_intel module is quickly reloaded.

Use the new static_key_deferred_flush() API to flush pending updates on
module unload.

Signed-off-by: David Matlack <dmatlack@google.com>
---
 arch/x86/kvm/lapic.c | 6 ++++++
 arch/x86/kvm/lapic.h | 1 +
 arch/x86/kvm/x86.c   | 1 +
 3 files changed, 8 insertions(+)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 34a66b2..1b80fa3 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2426,3 +2426,9 @@ void kvm_lapic_init(void)
 	jump_label_rate_limit(&apic_hw_disabled, HZ);
 	jump_label_rate_limit(&apic_sw_disabled, HZ);
 }
+
+void kvm_lapic_exit(void)
+{
+	static_key_deferred_flush(&apic_hw_disabled);
+	static_key_deferred_flush(&apic_sw_disabled);
+}
diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
index e0c8023..ff8039d 100644
--- a/arch/x86/kvm/lapic.h
+++ b/arch/x86/kvm/lapic.h
@@ -110,6 +110,7 @@ static inline bool kvm_hv_vapic_assist_page_enabled(struct kvm_vcpu *vcpu)
 
 int kvm_lapic_enable_pv_eoi(struct kvm_vcpu *vcpu, u64 data);
 void kvm_lapic_init(void);
+void kvm_lapic_exit(void);
 
 #define VEC_POS(v) ((v) & (32 - 1))
 #define REG_POS(v) (((v) >> 5) << 4)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8f86c0c..da386bf 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6007,6 +6007,7 @@ int kvm_arch_init(void *opaque)
 
 void kvm_arch_exit(void)
 {
+	kvm_lapic_exit();
 	perf_unregister_guest_info_callbacks(&kvm_guest_cbs);
 
 	if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
-- 
2.8.0.rc3.226.g39d4020