linux-kernel - [PATCH v6 42/44] KVM: VMX: Dedup code for adding MSR to VMCS's auto list

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Message-ID: <20251206001720.468579-43-seanjc@google.com>
Date: Fri,  5 Dec 2025 16:17:18 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Marc Zyngier <maz@...nel.org>, Oliver Upton <oupton@...nel.org>, 
	Tianrui Zhao <zhaotianrui@...ngson.cn>, Bibo Mao <maobibo@...ngson.cn>, 
	Huacai Chen <chenhuacai@...nel.org>, Anup Patel <anup@...infault.org>, 
	Paul Walmsley <pjw@...nel.org>, Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
	Xin Li <xin@...or.com>, "H. Peter Anvin" <hpa@...or.com>, Andy Lutomirski <luto@...nel.org>, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
	kvm@...r.kernel.org, loongarch@...ts.linux.dev, kvm-riscv@...ts.infradead.org, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, Mingwei Zhang <mizhang@...gle.com>, 
	Xudong Hao <xudong.hao@...el.com>, Sandipan Das <sandipan.das@....com>, 
	Dapeng Mi <dapeng1.mi@...ux.intel.com>, Xiong Zhang <xiong.y.zhang@...ux.intel.com>, 
	Manali Shukla <manali.shukla@....com>, Jim Mattson <jmattson@...gle.com>
Subject: [PATCH v6 42/44] KVM: VMX: Dedup code for adding MSR to VMCS's auto list

Add a helper to add an MSR to a VMCS's "auto" list to deduplicate the code
in add_atomic_switch_msr(), and so that the functionality can be used in
the future for managing the MSR auto-store list.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/vmx/vmx.c | 41 +++++++++++++++++++----------------------
 1 file changed, 19 insertions(+), 22 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 018e01daab68..3f64d4b1b19c 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1093,12 +1093,28 @@ static __always_inline void add_atomic_switch_msr_special(struct vcpu_vmx *vmx,
 	vm_exit_controls_setbit(vmx, exit);
 }
 
+static void vmx_add_auto_msr(struct vmx_msrs *m, u32 msr, u64 value,
+			     unsigned long vmcs_count_field, struct kvm *kvm)
+{
+	int i;
+
+	i = vmx_find_loadstore_msr_slot(m, msr);
+	if (i < 0) {
+		if (KVM_BUG_ON(m->nr == MAX_NR_LOADSTORE_MSRS, kvm))
+			return;
+
+		i = m->nr++;
+		m->val[i].index = msr;
+		vmcs_write32(vmcs_count_field, m->nr);
+	}
+	m->val[i].value = value;
+}
+
 static void add_atomic_switch_msr(struct vcpu_vmx *vmx, unsigned msr,
 				  u64 guest_val, u64 host_val)
 {
 	struct msr_autoload *m = &vmx->msr_autoload;
 	struct kvm *kvm = vmx->vcpu.kvm;
-	int i;
 
 	switch (msr) {
 	case MSR_EFER:
@@ -1132,27 +1148,8 @@ static void add_atomic_switch_msr(struct vcpu_vmx *vmx, unsigned msr,
 		wrmsrq(MSR_IA32_PEBS_ENABLE, 0);
 	}
 
-	i = vmx_find_loadstore_msr_slot(&m->guest, msr);
-	if (i < 0) {
-		if (KVM_BUG_ON(m->guest.nr == MAX_NR_LOADSTORE_MSRS, kvm))
-			return;
-
-		i = m->guest.nr++;
-		m->guest.val[i].index = msr;
-		vmcs_write32(VM_ENTRY_MSR_LOAD_COUNT, m->guest.nr);
-	}
-	m->guest.val[i].value = guest_val;
-
-	i = vmx_find_loadstore_msr_slot(&m->host, msr);
-	if (i < 0) {
-		if (KVM_BUG_ON(m->host.nr == MAX_NR_LOADSTORE_MSRS, kvm))
-			return;
-
-		i = m->host.nr++;
-		m->host.val[i].index = msr;
-		vmcs_write32(VM_EXIT_MSR_LOAD_COUNT, m->host.nr);
-	}
-	m->host.val[i].value = host_val;
+	vmx_add_auto_msr(&m->guest, msr, guest_val, VM_ENTRY_MSR_LOAD_COUNT, kvm);
+	vmx_add_auto_msr(&m->guest, msr, host_val, VM_EXIT_MSR_LOAD_COUNT, kvm);
 }
 
 static bool update_transition_efer(struct vcpu_vmx *vmx)
-- 
2.52.0.223.gf5cc29aaa4-goog