linux-kernel - [PATCH v6 35/44] KVM: VMX: Drop intermediate "guest" field from msr

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Message-ID: <20251206001720.468579-36-seanjc@google.com>
Date: Fri,  5 Dec 2025 16:17:11 -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 35/44] KVM: VMX: Drop intermediate "guest" field from msr_autostore

Drop the intermediate "guest" field from vcpu_vmx.msr_autostore as the
value saved on VM-Exit isn't guaranteed to be the guest's value, it's
purely whatever is in hardware at the time of VM-Exit.  E.g. KVM's only
use of the store list at the momemnt is to snapshot TSC at VM-Exit, and
the value saved is always the raw TSC even if TSC-offseting and/or
TSC-scaling is enabled for the guest.

And unlike msr_autoload, there is no need differentiate between "on-entry"
and "on-exit".

No functional change intended.

Cc: Jim Mattson <jmattson@...gle.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/vmx/nested.c | 10 +++++-----
 arch/x86/kvm/vmx/vmx.c    |  2 +-
 arch/x86/kvm/vmx/vmx.h    |  4 +---
 3 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 729cc1f05ac8..486789dac515 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -1076,11 +1076,11 @@ static bool nested_vmx_get_vmexit_msr_value(struct kvm_vcpu *vcpu,
 	 * VM-exit in L0, use the more accurate value.
 	 */
 	if (msr_index == MSR_IA32_TSC) {
-		int i = vmx_find_loadstore_msr_slot(&vmx->msr_autostore.guest,
+		int i = vmx_find_loadstore_msr_slot(&vmx->msr_autostore,
 						    MSR_IA32_TSC);
 
 		if (i >= 0) {
-			u64 val = vmx->msr_autostore.guest.val[i].value;
+			u64 val = vmx->msr_autostore.val[i].value;
 
 			*data = kvm_read_l1_tsc(vcpu, val);
 			return true;
@@ -1167,7 +1167,7 @@ static void prepare_vmx_msr_autostore_list(struct kvm_vcpu *vcpu,
 					   u32 msr_index)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
-	struct vmx_msrs *autostore = &vmx->msr_autostore.guest;
+	struct vmx_msrs *autostore = &vmx->msr_autostore;
 	bool in_vmcs12_store_list;
 	int msr_autostore_slot;
 	bool in_autostore_list;
@@ -2366,7 +2366,7 @@ static void prepare_vmcs02_constant_state(struct vcpu_vmx *vmx)
 	 * addresses are constant (for vmcs02), the counts can change based
 	 * on L2's behavior, e.g. switching to/from long mode.
 	 */
-	vmcs_write64(VM_EXIT_MSR_STORE_ADDR, __pa(vmx->msr_autostore.guest.val));
+	vmcs_write64(VM_EXIT_MSR_STORE_ADDR, __pa(vmx->msr_autostore.val));
 	vmcs_write64(VM_EXIT_MSR_LOAD_ADDR, __pa(vmx->msr_autoload.host.val));
 	vmcs_write64(VM_ENTRY_MSR_LOAD_ADDR, __pa(vmx->msr_autoload.guest.val));
 
@@ -2704,7 +2704,7 @@ static void prepare_vmcs02_rare(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12)
 	 */
 	prepare_vmx_msr_autostore_list(&vmx->vcpu, MSR_IA32_TSC);
 
-	vmcs_write32(VM_EXIT_MSR_STORE_COUNT, vmx->msr_autostore.guest.nr);
+	vmcs_write32(VM_EXIT_MSR_STORE_COUNT, vmx->msr_autostore.nr);
 	vmcs_write32(VM_EXIT_MSR_LOAD_COUNT, vmx->msr_autoload.host.nr);
 	vmcs_write32(VM_ENTRY_MSR_LOAD_COUNT, vmx->msr_autoload.guest.nr);
 
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 62ba2a2b9e98..23c92c41fd83 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6567,7 +6567,7 @@ void dump_vmcs(struct kvm_vcpu *vcpu)
 	if (vmcs_read32(VM_ENTRY_MSR_LOAD_COUNT) > 0)
 		vmx_dump_msrs("guest autoload", &vmx->msr_autoload.guest);
 	if (vmcs_read32(VM_EXIT_MSR_STORE_COUNT) > 0)
-		vmx_dump_msrs("guest autostore", &vmx->msr_autostore.guest);
+		vmx_dump_msrs("autostore", &vmx->msr_autostore);
 
 	if (vmentry_ctl & VM_ENTRY_LOAD_CET_STATE)
 		pr_err("S_CET = 0x%016lx, SSP = 0x%016lx, SSP TABLE = 0x%016lx\n",
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index d7a96c84371f..4ce653d729ca 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -245,9 +245,7 @@ struct vcpu_vmx {
 		struct vmx_msrs host;
 	} msr_autoload;
 
-	struct msr_autostore {
-		struct vmx_msrs guest;
-	} msr_autostore;
+	struct vmx_msrs msr_autostore;
 
 	struct {
 		int vm86_active;
-- 
2.52.0.223.gf5cc29aaa4-goog