linux-kernel - [PATCH RFC v1 08/20] KVM: VMX: Support extended register index in exit handling

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Message-ID: <20251110180131.28264-9-chang.seok.bae@intel.com>
Date: Mon, 10 Nov 2025 18:01:19 +0000
From: "Chang S. Bae" <chang.seok.bae@...el.com>
To: kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: pbonzini@...hat.com,
	seanjc@...gle.com,
	chao.gao@...el.com,
	zhao1.liu@...el.com,
	chang.seok.bae@...el.com
Subject: [PATCH RFC v1 08/20] KVM: VMX: Support extended register index in exit handling

Support to 5-bit register indices in VMCS fields when EGPRs are enabled.

Signed-off-by: Chang S. Bae <chang.seok.bae@...el.com>
---
RFC note:
The "chicken bit" (XCR0.APX) checker is intentionally deferred, as the
emulator in the next series will do a similar check. Consolidating the
XCR0 handling at the end keeps the logic clearer during the feature
exposition.
---
 arch/x86/kvm/vmx/vmx.h | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index b8da6ebc35dc..6cf1eb739caf 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -374,12 +374,17 @@ struct vmx_insn_info {
 
 static inline bool vmx_egpr_enabled(struct kvm_vcpu *vcpu __maybe_unused) { return false; }
 
-static inline struct vmx_insn_info vmx_get_insn_info(struct kvm_vcpu *vcpu __maybe_unused)
+static inline struct vmx_insn_info vmx_get_insn_info(struct kvm_vcpu *vcpu)
 {
 	struct vmx_insn_info insn;
 
-	insn.extended  = false;
-	insn.info.word = vmcs_read32(VMX_INSTRUCTION_INFO);
+	if (vmx_egpr_enabled(vcpu)) {
+		insn.extended   = true;
+		insn.info.dword = vmcs_read64(EXTENDED_INSTRUCTION_INFO);
+	} else {
+		insn.extended  = false;
+		insn.info.word = vmcs_read32(VMX_INSTRUCTION_INFO);
+	}
 
 	return insn;
 }
@@ -415,7 +420,10 @@ static __always_inline unsigned long vmx_get_exit_qual(struct kvm_vcpu *vcpu)
 
 static inline int vmx_get_exit_qual_gpr(struct kvm_vcpu *vcpu)
 {
-	return (vmx_get_exit_qual(vcpu) >> 8) & 0xf;
+	if (vmx_egpr_enabled(vcpu))
+		return (vmx_get_exit_qual(vcpu) >> 8) & 0x1f;
+	else
+		return (vmx_get_exit_qual(vcpu) >> 8) & 0xf;
 }
 
 static __always_inline u32 vmx_get_intr_info(struct kvm_vcpu *vcpu)
-- 
2.51.0