linux-kernel - [RFC PATCH v7 01/37] KVM: lapic: Remove __apic_test_and_{set|clear}

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Message-ID: <20250610175424.209796-2-Neeraj.Upadhyay@amd.com>
Date: Tue, 10 Jun 2025 23:23:48 +0530
From: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
To: <linux-kernel@...r.kernel.org>
CC: <bp@...en8.de>, <tglx@...utronix.de>, <mingo@...hat.com>,
	<dave.hansen@...ux.intel.com>, <Thomas.Lendacky@....com>, <nikunj@....com>,
	<Santosh.Shukla@....com>, <Vasant.Hegde@....com>,
	<Suravee.Suthikulpanit@....com>, <David.Kaplan@....com>, <x86@...nel.org>,
	<hpa@...or.com>, <peterz@...radead.org>, <seanjc@...gle.com>,
	<pbonzini@...hat.com>, <kvm@...r.kernel.org>,
	<kirill.shutemov@...ux.intel.com>, <huibo.wang@....com>,
	<naveen.rao@....com>, <francescolavra.fl@...il.com>, <tiala@...rosoft.com>
Subject: [RFC PATCH v7 01/37] KVM: lapic: Remove __apic_test_and_{set|clear}_vector()

Remove __apic_test_and_set_vector() and __apic_test_and_clear_vector(),
because the _only_ register that's safe to modify with a non-atomic
operation is ISR, because KVM isn't running the vCPU, i.e. hardware can't
service an IRQ or process an EOI for the relevant (virtual) APIC.

No functional change intended.

Suggested-by: Sean Christopherson <seanjc@...gle.com>
[Neeraj: Add "inline" for apic_vector_to_isr()]
Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
---
Changes since v6:

 - New change.

 arch/x86/kvm/lapic.c | 19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 73418dc0ebb2..11e57f351ce5 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -125,16 +125,6 @@ bool kvm_apic_pending_eoi(struct kvm_vcpu *vcpu, int vector)
 		apic_test_vector(vector, apic->regs + APIC_IRR);
 }
 
-static inline int __apic_test_and_set_vector(int vec, void *bitmap)
-{
-	return __test_and_set_bit(VEC_POS(vec), (bitmap) + REG_POS(vec));
-}
-
-static inline int __apic_test_and_clear_vector(int vec, void *bitmap)
-{
-	return __test_and_clear_bit(VEC_POS(vec), (bitmap) + REG_POS(vec));
-}
-
 __read_mostly DEFINE_STATIC_KEY_FALSE(kvm_has_noapic_vcpu);
 EXPORT_SYMBOL_GPL(kvm_has_noapic_vcpu);
 
@@ -744,9 +734,14 @@ void kvm_apic_clear_irr(struct kvm_vcpu *vcpu, int vec)
 }
 EXPORT_SYMBOL_GPL(kvm_apic_clear_irr);
 
+static inline void *apic_vector_to_isr(int vec, struct kvm_lapic *apic)
+{
+	return apic->regs + APIC_ISR + REG_POS(vec);
+}
+
 static inline void apic_set_isr(int vec, struct kvm_lapic *apic)
 {
-	if (__apic_test_and_set_vector(vec, apic->regs + APIC_ISR))
+	if (__test_and_set_bit(VEC_POS(vec), apic_vector_to_isr(vec, apic)))
 		return;
 
 	/*
@@ -789,7 +784,7 @@ static inline int apic_find_highest_isr(struct kvm_lapic *apic)
 
 static inline void apic_clear_isr(int vec, struct kvm_lapic *apic)
 {
-	if (!__apic_test_and_clear_vector(vec, apic->regs + APIC_ISR))
+	if (!__test_and_clear_bit(VEC_POS(vec), apic_vector_to_isr(vec, apic)))
 		return;
 
 	/*
-- 
2.34.1