i386/cpu: Unify family, model and stepping calculation for x86 CPU

There are multiple places where CPUID family/model/stepping info
are retrieved from env->cpuid_version.

Besides, the calculation of family and model inside host_cpu_vendor_fms()
doesn't comply to what Intel and AMD define. For family, both Intel
and AMD define that Extended Family ID needs to be counted only when
(base) Family is 0xF. For model, Intel counts Extended Model when
(base) Family is 0x6 or 0xF, while AMD counts EXtended MOdel when
(base) Family is 0xF.

Introduce generic helper functions to get family, model and stepping
from the EAX value of CPUID leaf 1, with the correct calculation
formula.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Link: https://lore.kernel.org/r/20250630080610.3151956-5-xiaoyao.li@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

4 files changed, 38 insertions, 12 deletions

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index d3d13b1..b768838 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -6325,10 +6325,7 @@ static void x86_cpuid_version_get_family(Object *obj, Visitor *v,
     CPUX86State *env = &cpu->env;
     uint64_t value;
 
-    value = (env->cpuid_version >> 8) & 0xf;
-    if (value == 0xf) {
-        value += (env->cpuid_version >> 20) & 0xff;
-    }
+    value = x86_cpu_family(env->cpuid_version);
     visit_type_uint64(v, name, &value, errp);
 }
 
@@ -6366,8 +6363,7 @@ static void x86_cpuid_version_get_model(Object *obj, Visitor *v,
     CPUX86State *env = &cpu->env;
     uint64_t value;
 
-    value = (env->cpuid_version >> 4) & 0xf;
-    value |= ((env->cpuid_version >> 16) & 0xf) << 4;
+    value = x86_cpu_model(env->cpuid_version);
     visit_type_uint64(v, name, &value, errp);
 }
 
@@ -6401,7 +6397,7 @@ static void x86_cpuid_version_get_stepping(Object *obj, Visitor *v,
     CPUX86State *env = &cpu->env;
     uint64_t value;
 
-    value = env->cpuid_version & 0xf;
+    value = x86_cpu_stepping(env->cpuid_version);
     visit_type_uint64(v, name, &value, errp);
 }
 
@@ -8155,7 +8151,7 @@ static void mce_init(X86CPU *cpu)
     CPUX86State *cenv = &cpu->env;
     unsigned int bank;
 
-    if (((cenv->cpuid_version >> 8) & 0xf) >= 6
+    if (x86_cpu_family(cenv->cpuid_version) >= 6
         && (cenv->features[FEAT_1_EDX] & (CPUID_MCE | CPUID_MCA)) ==
             (CPUID_MCE | CPUID_MCA)) {
         cenv->mcg_cap = MCE_CAP_DEF | MCE_BANKS_DEF |
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index b3bb988..a580562 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -2678,6 +2678,36 @@ static inline int32_t x86_get_a20_mask(CPUX86State *env)
     }
 }
 
+static inline uint32_t x86_cpu_family(uint32_t eax)
+{
+    uint32_t family = (eax >> 8) & 0xf;
+
+    if (family == 0xf) {
+        family += (eax >> 20) & 0xff;
+    }
+
+    return family;
+}
+
+static inline uint32_t x86_cpu_model(uint32_t eax)
+{
+    uint32_t family, model;
+
+    family = x86_cpu_family(eax);
+    model = (eax >> 4) & 0xf;
+
+    if (family >= 0x6) {
+        model += ((eax >> 16) & 0xf) << 4;
+    }
+
+    return model;
+}
+
+static inline uint32_t x86_cpu_stepping(uint32_t eax)
+{
+    return eax & 0xf;
+}
+
 static inline bool cpu_has_vmx(CPUX86State *env)
 {
     return env->features[FEAT_1_ECX] & CPUID_EXT_VMX;
diff --git a/target/i386/host-cpu.c b/target/i386/host-cpu.c
index b1fb6d6..d5e2bb5 100644
--- a/target/i386/host-cpu.c
+++ b/target/i386/host-cpu.c
@@ -117,13 +117,13 @@ void host_cpu_vendor_fms(char *vendor, int *family, int *model, int *stepping)
 
     host_cpuid(0x1, 0, &eax, &ebx, &ecx, &edx);
     if (family) {
-        *family = ((eax >> 8) & 0x0F) + ((eax >> 20) & 0xFF);
+        *family = x86_cpu_family(eax);
     }
     if (model) {
-        *model = ((eax >> 4) & 0x0F) | ((eax & 0xF0000) >> 12);
+        *model = x86_cpu_model(eax);
     }
     if (stepping) {
-        *stepping = eax & 0x0F;
+        *stepping = x86_cpu_stepping(eax);
     }
 }
 
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index fc58a23..e8c8be0 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -2259,7 +2259,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
     cpuid_i = kvm_x86_build_cpuid(env, cpuid_data.entries, cpuid_i);
     cpuid_data.cpuid.nent = cpuid_i;
 
-    if (((env->cpuid_version >> 8)&0xF) >= 6
+    if (x86_cpu_family(env->cpuid_version) >= 6
         && (env->features[FEAT_1_EDX] & (CPUID_MCE | CPUID_MCA)) ==
            (CPUID_MCE | CPUID_MCA)) {
         uint64_t mcg_cap, unsupported_caps;