[PATCH v4 06/38] x86/irq: Factor out common code for installing kvm irq handler

From: Mingwei Zhang
Date: Mon Mar 24 2025 - 13:36:54 EST


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 6c56d5235f0f..00ac94535c21 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -8279,7 +8279,7 @@ 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();
@@ -8583,7 +8583,7 @@ __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;
}
--
2.49.0.395.g12beb8f557-goog