KVM: Split cpuid register access from computation

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@redhat.com>

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 61ccbdf..197afd5 100644 (file)
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -640,33 +640,37 @@ 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);
-       }
+               *eax = best->eax;
+               *ebx = best->ebx;
+               *ecx = best->ecx;
+               *edx = best->edx;
+       } else
+               *eax = *ebx = *ecx = *edx = 0;
+}
+
+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,
-                       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));
+       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 (file)
--- 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)