[RFC PATCH v3 11/58] x86/irq: Factor out common code for installing kvm irq handler

[Mingwei Zhang <mizhang@xxxxxxxxxx>]

From: Xiong Zhang <xiong.y.zhang@xxxxxxxxxxxxxxx>

KVM will register irq handler for POSTED_INTR_WAKEUP_VECTOR and
KVM_GUEST_PMI_VECTOR, the existing kvm_set_posted_intr_wakeup_handler() is
renamed to x86_set_kvm_irq_handler(), and vector input parameter is used
to distinguish POSTED_INTR_WARKUP_VECTOR and KVM_GUEST_PMI_VECTOR.

Caller should call x86_set_kvm_irq_handler() once to register
a non-dummy handler for each vector. If caller register one
handler for a vector, later the caller register the same or different
non-dummy handler again, the second call will output warn message.

Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Xiong Zhang <xiong.y.zhang@xxxxxxxxxxxxxxx>
Tested-by: Yongwei Ma <yongwei.ma@xxxxxxxxx>
Signed-off-by: Mingwei Zhang <mizhang@xxxxxxxxxx>
---
 arch/x86/include/asm/irq.h |  2 +-
 arch/x86/kernel/irq.c      | 18 ++++++++++++------
 arch/x86/kvm/vmx/vmx.c     |  4 ++--
 3 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/irq.h b/arch/x86/include/asm/irq.h
index 194dfff84cb1..050a247b69b4 100644
--- a/arch/x86/include/asm/irq.h
+++ b/arch/x86/include/asm/irq.h
@@ -30,7 +30,7 @@ struct irq_desc;
 extern void fixup_irqs(void);
 
 #if IS_ENABLED(CONFIG_KVM)
-extern void kvm_set_posted_intr_wakeup_handler(void (*handler)(void));
+void x86_set_kvm_irq_handler(u8 vector, void (*handler)(void));
 #endif
 
 extern void (*x86_platform_ipi_callback)(void);
diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 385e3a5fc304..18cd418fe106 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -312,16 +312,22 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_x86_platform_ipi)
 static void dummy_handler(void) {}
 static void (*kvm_posted_intr_wakeup_handler)(void) = dummy_handler;
 
-void kvm_set_posted_intr_wakeup_handler(void (*handler)(void))
+void x86_set_kvm_irq_handler(u8 vector, void (*handler)(void))
 {
-	if (handler)
+	if (!handler)
+		handler = dummy_handler;
+
+	if (vector == POSTED_INTR_WAKEUP_VECTOR &&
+	    (handler == dummy_handler ||
+	     kvm_posted_intr_wakeup_handler == dummy_handler))
 		kvm_posted_intr_wakeup_handler = handler;
-	else {
-		kvm_posted_intr_wakeup_handler = dummy_handler;
+	else
+		WARN_ON_ONCE(1);
+
+	if (handler == dummy_handler)
 		synchronize_rcu();
-	}
 }
-EXPORT_SYMBOL_GPL(kvm_set_posted_intr_wakeup_handler);
+EXPORT_SYMBOL_GPL(x86_set_kvm_irq_handler);
 
 /*
  * Handler for POSTED_INTERRUPT_VECTOR.
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index b3c83c06f826..ad465881b043 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -8292,7 +8292,7 @@ void vmx_migrate_timers(struct kvm_vcpu *vcpu)
 
 void vmx_hardware_unsetup(void)
 {
-	kvm_set_posted_intr_wakeup_handler(NULL);
+	x86_set_kvm_irq_handler(POSTED_INTR_WAKEUP_VECTOR, NULL);
 
 	if (nested)
 		nested_vmx_hardware_unsetup();
@@ -8602,7 +8602,7 @@ __init int vmx_hardware_setup(void)
 	if (r && nested)
 		nested_vmx_hardware_unsetup();
 
-	kvm_set_posted_intr_wakeup_handler(pi_wakeup_handler);
+	x86_set_kvm_irq_handler(POSTED_INTR_WAKEUP_VECTOR, pi_wakeup_handler);
 
 	return r;
 }
-- 
2.46.0.rc1.232.g9752f9e123-goog