linux-kernel - [PATCH v3 2/9] KVM: x86: Move pv_unhaulted check out of kvm_vcpu_has

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Message-ID: <20250222014225.897298-3-binbin.wu@linux.intel.com>
Date: Sat, 22 Feb 2025 09:42:18 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: pbonzini@...hat.com,
	seanjc@...gle.com,
	kvm@...r.kernel.org
Cc: rick.p.edgecombe@...el.com,
	kai.huang@...el.com,
	adrian.hunter@...el.com,
	reinette.chatre@...el.com,
	xiaoyao.li@...el.com,
	tony.lindgren@...el.com,
	isaku.yamahata@...el.com,
	yan.y.zhao@...el.com,
	chao.gao@...el.com,
	linux-kernel@...r.kernel.org,
	binbin.wu@...ux.intel.com
Subject: [PATCH v3 2/9] KVM: x86: Move pv_unhaulted check out of kvm_vcpu_has_events()

Move pv_unhaulted check out of kvm_vcpu_has_events(), check pv_unhaulted
explicitly when handling PV unhalt and expose kvm_vcpu_has_events().

kvm_vcpu_has_events() returns true if pv_unhalted is set, and pv_unhalted
is only cleared on transitions to KVM_MP_STATE_RUNNABLE.  If the guest
initiates a spurious wakeup, pv_unhalted could be left set in perpetuity.
Currently, this is not problematic because kvm_vcpu_has_events() is only
called when handling PV unhalt.  However, if kvm_vcpu_has_events() is used
for other purposes in the future, it could return the unexpected results.

Export kvm_vcpu_has_events() for its usage in broader contexts.

Suggested-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Binbin Wu <binbin.wu@...ux.intel.com>
---
Hypercalls exit to userspace v3:
- New added.
---
 arch/x86/kvm/x86.c       | 11 +++++------
 include/linux/kvm_host.h |  1 +
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 62dded70932d..8877d6db9b84 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11133,7 +11133,7 @@ static bool kvm_vcpu_running(struct kvm_vcpu *vcpu)
 		!vcpu->arch.apf.halted);
 }
 
-static bool kvm_vcpu_has_events(struct kvm_vcpu *vcpu)
+bool kvm_vcpu_has_events(struct kvm_vcpu *vcpu)
 {
 	if (!list_empty_careful(&vcpu->async_pf.done))
 		return true;
@@ -11142,9 +11142,6 @@ static bool kvm_vcpu_has_events(struct kvm_vcpu *vcpu)
 	    kvm_apic_init_sipi_allowed(vcpu))
 		return true;
 
-	if (vcpu->arch.pv.pv_unhalted)
-		return true;
-
 	if (kvm_is_exception_pending(vcpu))
 		return true;
 
@@ -11182,10 +11179,12 @@ static bool kvm_vcpu_has_events(struct kvm_vcpu *vcpu)
 
 	return false;
 }
+EXPORT_SYMBOL_GPL(kvm_vcpu_has_events);
 
 int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
 {
-	return kvm_vcpu_running(vcpu) || kvm_vcpu_has_events(vcpu);
+	return kvm_vcpu_running(vcpu) || vcpu->arch.pv.pv_unhalted ||
+	       kvm_vcpu_has_events(vcpu);
 }
 
 /* Called within kvm->srcu read side.  */
@@ -11321,7 +11320,7 @@ static int __kvm_emulate_halt(struct kvm_vcpu *vcpu, int state, int reason)
 	 */
 	++vcpu->stat.halt_exits;
 	if (lapic_in_kernel(vcpu)) {
-		if (kvm_vcpu_has_events(vcpu))
+		if (kvm_vcpu_has_events(vcpu) || vcpu->arch.pv.pv_unhalted)
 			vcpu->arch.pv.pv_unhalted = false;
 		else
 			vcpu->arch.mp_state = state;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 3bfe3140f444..ed1968f6f841 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1609,6 +1609,7 @@ void kvm_arch_disable_virtualization(void);
 int kvm_arch_enable_virtualization_cpu(void);
 void kvm_arch_disable_virtualization_cpu(void);
 #endif
+bool kvm_vcpu_has_events(struct kvm_vcpu *vcpu);
 int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu);
 bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu);
 int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu);
-- 
2.46.0