[PATCH v3 11/20] KVM: nVMX: Propagate the extended instruction info field

Chang S. Bae
2026-04-28T05:26:27Z

Define the new extended_instruction_info field in struct vmcs12 and
propagate it to nested VMX. Gate the propagation on the guest APX
enumeration, which aligns with VMX behavior. Thus, define the CPUID bit
here too.

Link: https://lore.kernel.org/aRvOSnaUt1E+%2FpkC@intel.com
Suggested-by: Chao Gao <chao.gao@intel.com>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
---
arch/x86/kvm/reverse_cpuid.h | 2 ++
arch/x86/kvm/vmx/nested.c | 6 ++++++
arch/x86/kvm/vmx/vmcs12.c | 1 +
arch/x86/kvm/vmx/vmcs12.h | 3 ++-
4 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h
index 657f5f743ed9..de90697c4e5a 100644
--- a/arch/x86/kvm/reverse_cpuid.h
+++ b/arch/x86/kvm/reverse_cpuid.h
@@ -35,6 +35,7 @@
#define X86_FEATURE_AVX_VNNI_INT16 KVM_X86_FEATURE(CPUID_7_1_EDX, 10)
#define X86_FEATURE_PREFETCHITI KVM_X86_FEATURE(CPUID_7_1_EDX, 14)
#define X86_FEATURE_AVX10 KVM_X86_FEATURE(CPUID_7_1_EDX, 19)
+#define KVM_X86_FEATURE_APX KVM_X86_FEATURE(CPUID_7_1_EDX, 21)

/* Intel-defined sub-features, CPUID level 0x00000007:2 (EDX) */
#define X86_FEATURE_INTEL_PSFD KVM_X86_FEATURE(CPUID_7_2_EDX, 0)
@@ -144,6 +145,7 @@ static __always_inline u32 __feature_translate(int x86_feature)
KVM_X86_TRANSLATE_FEATURE(SGX1);
KVM_X86_TRANSLATE_FEATURE(SGX2);
KVM_X86_TRANSLATE_FEATURE(SGX_EDECCSSA);
+ KVM_X86_TRANSLATE_FEATURE(APX);
KVM_X86_TRANSLATE_FEATURE(CONSTANT_TSC);
KVM_X86_TRANSLATE_FEATURE(PERFMON_V2);
KVM_X86_TRANSLATE_FEATURE(RRSBA_CTRL);
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index a1ecde280ecc..498b291c73bd 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4748,6 +4748,12 @@ static void prepare_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
vmcs12->vm_exit_intr_info = exit_intr_info;
vmcs12->vm_exit_instruction_len = exit_insn_len;
vmcs12->vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
+ /*
+ * The APX enumeration guarantees the presence of the extended
+ * fields. This CPUID bit alone is sufficient to rely on it.
+ */
+ if (guest_cpu_cap_has(vcpu, X86_FEATURE_APX))
+ vmcs12->extended_instruction_info = vmcs_read64(EXTENDED_INSTRUCTION_INFO);

/*
* According to spec, there's no need to store the guest's
diff --git a/arch/x86/kvm/vmx/vmcs12.c b/arch/x86/kvm/vmx/vmcs12.c
index 1ebe67c384ad..267aa64f005e 100644
--- a/arch/x86/kvm/vmx/vmcs12.c
+++ b/arch/x86/kvm/vmx/vmcs12.c
@@ -53,6 +53,7 @@ static const u16 kvm_supported_vmcs12_field_offsets[] __initconst = {
FIELD64(XSS_EXIT_BITMAP, xss_exit_bitmap),
FIELD64(ENCLS_EXITING_BITMAP, encls_exiting_bitmap),
FIELD64(GUEST_PHYSICAL_ADDRESS, guest_physical_address),
+ FIELD64(EXTENDED_INSTRUCTION_INFO, extended_instruction_info),
FIELD64(VMCS_LINK_POINTER, vmcs_link_pointer),
FIELD64(GUEST_IA32_DEBUGCTL, guest_ia32_debugctl),
FIELD64(GUEST_IA32_PAT, guest_ia32_pat),
diff --git a/arch/x86/kvm/vmx/vmcs12.h b/arch/x86/kvm/vmx/vmcs12.h
index 21cd1b75e4fd..25e9a41c248f 100644
--- a/arch/x86/kvm/vmx/vmcs12.h
+++ b/arch/x86/kvm/vmx/vmcs12.h
@@ -71,7 +71,7 @@ struct __packed vmcs12 {
u64 pml_address;
u64 encls_exiting_bitmap;
u64 tsc_multiplier;
- u64 padding64[1]; /* room for future expansion */
+ u64 extended_instruction_info;
/*
* To allow migration of L1 (complete with its L2 guests) between
* machines of different natural widths (32 or 64 bit), we cannot have
@@ -261,6 +261,7 @@ static inline void vmx_check_vmcs12_offsets(void)
CHECK_OFFSET(pml_address, 312);
CHECK_OFFSET(encls_exiting_bitmap, 320);
CHECK_OFFSET(tsc_multiplier, 328);
+ CHECK_OFFSET(extended_instruction_info, 336);
CHECK_OFFSET(cr0_guest_host_mask, 344);
CHECK_OFFSET(cr4_guest_host_mask, 352);
CHECK_OFFSET(cr0_read_shadow, 360);
--
2.51.0