[PATCH v6 35/44] KVM: VMX: Drop intermediate "guest" field from msr_autostore

Sean Christopherson
2025-12-06T00:18:37Z

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@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.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