linux-kernel - [PATCH RFC v1 06/20] KVM: VMX: Refactor GPR index retrieval from exit qualification

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Message-ID: <20251110180131.28264-7-chang.seok.bae@intel.com>
Date: Mon, 10 Nov 2025 18:01:17 +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 06/20] KVM: VMX: Refactor GPR index retrieval from exit qualification

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

Some VMX exit qualification, in addition to the VMX instruction info
field, encode 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>
---
 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 4b883ded6c4b..97ec8e594155 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -6404,7 +6404,7 @@ 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 dd8c9517c38c..4405724cb874 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5459,7 +5459,7 @@ 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 a58d9187ed1d..64a0772c883c 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