[PATCH v2 02/26] KVM: Split cpuid register access from computation

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Introduce kvm_cpuid() to perform the leaf limit check and calculate
register values, and let kvm_emulate_cpuid() just handle reading and
writing the registers from/to the vcpu.  This allows us to reuse
kvm_cpuid() in a context where directly reading and writing registers
is not desired.

Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
---
 arch/x86/kvm/cpuid.c | 38 ++++++++++++++++++++++++--------------
 arch/x86/kvm/cpuid.h |  1 +
 2 files changed, 25 insertions(+), 14 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 7df1c6d..44476fb 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -639,33 +639,43 @@ static struct kvm_cpuid_entry2* check_cpuid_limit(struct kvm_vcpu *vcpu,
 	return kvm_find_cpuid_entry(vcpu, maxlevel->eax, index);
 }
 
-void kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
+void kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, u32 *ecx, u32 *edx)
 {
-	u32 function, index;
+	u32 function = *eax, index = *ecx;
 	struct kvm_cpuid_entry2 *best;
 
-	function = kvm_register_read(vcpu, VCPU_REGS_RAX);
-	index = kvm_register_read(vcpu, VCPU_REGS_RCX);
-	kvm_register_write(vcpu, VCPU_REGS_RAX, 0);
-	kvm_register_write(vcpu, VCPU_REGS_RBX, 0);
-	kvm_register_write(vcpu, VCPU_REGS_RCX, 0);
-	kvm_register_write(vcpu, VCPU_REGS_RDX, 0);
 	best = kvm_find_cpuid_entry(vcpu, function, index);
 
 	if (!best)
 		best = check_cpuid_limit(vcpu, function, index);
 
 	if (best) {
-		kvm_register_write(vcpu, VCPU_REGS_RAX, best->eax);
-		kvm_register_write(vcpu, VCPU_REGS_RBX, best->ebx);
-		kvm_register_write(vcpu, VCPU_REGS_RCX, best->ecx);
-		kvm_register_write(vcpu, VCPU_REGS_RDX, best->edx);
-	}
-	kvm_x86_ops->skip_emulated_instruction(vcpu);
+		*eax = best->eax;
+		*ebx = best->ebx;
+		*ecx = best->ecx;
+		*edx = best->edx;
+	} else
+		*eax = *ebx = *ecx = *edx = 0;
+
 	trace_kvm_cpuid(function,
 			kvm_register_read(vcpu, VCPU_REGS_RAX),
 			kvm_register_read(vcpu, VCPU_REGS_RBX),
 			kvm_register_read(vcpu, VCPU_REGS_RCX),
 			kvm_register_read(vcpu, VCPU_REGS_RDX));
 }
+
+void kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
+{
+	u32 function, eax, ebx, ecx, edx;
+
+	function = eax = kvm_register_read(vcpu, VCPU_REGS_RAX);
+	ecx = kvm_register_read(vcpu, VCPU_REGS_RCX);
+	kvm_cpuid(vcpu, &eax, &ebx, &ecx, &edx);
+	kvm_register_write(vcpu, VCPU_REGS_RAX, eax);
+	kvm_register_write(vcpu, VCPU_REGS_RBX, ebx);
+	kvm_register_write(vcpu, VCPU_REGS_RCX, ecx);
+	kvm_register_write(vcpu, VCPU_REGS_RDX, edx);
+	kvm_x86_ops->skip_emulated_instruction(vcpu);
+	trace_kvm_cpuid(function, eax, ebx, ecx, edx);
+}
 EXPORT_SYMBOL_GPL(kvm_emulate_cpuid);
diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
index 26d1fb4..f449edc 100644
--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -17,6 +17,7 @@ int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu,
 int kvm_vcpu_ioctl_get_cpuid2(struct kvm_vcpu *vcpu,
 			      struct kvm_cpuid2 *cpuid,
 			      struct kvm_cpuid_entry2 __user *entries);
+void kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, u32 *ecx, u32 *edx);
 
 
 static inline bool guest_cpuid_has_xsave(struct kvm_vcpu *vcpu)
-- 
1.7.11

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