linux-kernel - [PATCH 06/16] KVM: VMX: Refactor GPR index retrieval from exit qualification

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Message-ID: <20251221040742.29749-7-chang.seok.bae@intel.com>
Date: Sun, 21 Dec 2025 04:07:32 +0000
From: "Chang S. Bae" <chang.seok.bae@...el.com>
To: pbonzini@...hat.com,
	seanjc@...gle.com
Cc: kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	chao.gao@...el.com,
	chang.seok.bae@...el.com
Subject: [PATCH 06/16] KVM: VMX: Refactor GPR index retrieval from exit qualification

Introduce a helper to extract the GPR index from the exit qualification
field.

VMX exit qualification, in addition to the VMX instruction info field,
encodes a GPR index. With the introduction of EGPRs, this field is
extended by a previously reserved bit position.

This refactoring centralizes the logic so that future updates can handle
the extended GPR index without code duplication.

Since the VMCS exit qualification is cached in VCPU state, it is safe
for the helper to access it directly via the VCPU pointer. This argument
will also be used later to determine EGPR availability.

No functional change intended.

Signed-off-by: Chang S. Bae <chang.seok.bae@...el.com>
---
No change since last version
---
 arch/x86/kvm/vmx/nested.c | 2 +-
 arch/x86/kvm/vmx/vmx.c    | 2 +-
 arch/x86/kvm/vmx/vmx.h    | 5 +++++
 3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 558f889db621..1e35e1923aec 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -6353,7 +6353,7 @@ static bool nested_vmx_exit_handled_cr(struct kvm_vcpu *vcpu,
 
 	switch ((exit_qualification >> 4) & 3) {
 	case 0: /* mov to cr */
-		reg = (exit_qualification >> 8) & 15;
+		reg = vmx_get_exit_qual_gpr(vcpu);
 		val = kvm_gpr_read(vcpu, reg);
 		switch (cr) {
 		case 0:
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index ae28b06b11f5..d41e710e8807 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5588,7 +5588,7 @@ static int handle_cr(struct kvm_vcpu *vcpu)
 
 	exit_qualification = vmx_get_exit_qual(vcpu);
 	cr = exit_qualification & 15;
-	reg = (exit_qualification >> 8) & 15;
+	reg = vmx_get_exit_qual_gpr(vcpu);
 	switch ((exit_qualification >> 4) & 3) {
 	case 0: /* mov to cr */
 		val = kvm_gpr_read(vcpu, reg);
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index ed02a8bcc15e..f8dbad161717 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -411,6 +411,11 @@ static __always_inline unsigned long vmx_get_exit_qual(struct kvm_vcpu *vcpu)
 	return vt->exit_qualification;
 }
 
+static inline int vmx_get_exit_qual_gpr(struct kvm_vcpu *vcpu)
+{
+	return (vmx_get_exit_qual(vcpu) >> 8) & 0xf;
+}
+
 static __always_inline u32 vmx_get_intr_info(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vt *vt = to_vt(vcpu);
-- 
2.51.0