From: Zhao Liu <zhao1.liu@intel.com>
Date: Fri, 27 Jun 2025 03:51:26 +0000 (+0800)
Subject: i386/cpu: Mark EBX/ECX/EDX in CPUID 0x80000000 leaf as reserved for Intel
X-Git-Tag: v10.1.0-rc0~21^2~9
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a539cd26145c726fddd19eb0e2c20332960b0245;p=thirdparty%2Fqemu.git

i386/cpu: Mark EBX/ECX/EDX in CPUID 0x80000000 leaf as reserved for Intel

Per SDM,

80000000H EAX Maximum Input Value for Extended Function CPUID Information.
          EBX Reserved.
          ECX Reserved.
          EDX Reserved.

EBX/ECX/EDX in CPUID 0x80000000 leaf are reserved. Intel is using 0x0
leaf to encode vendor.

Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Tao Su <tao1.su@linux.intel.com>
Link: https://lore.kernel.org/r/20250627035129.2755537-2-zhao1.liu@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 4f0c973446..ae508fa962 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -8280,9 +8280,15 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
         break;
     case 0x80000000:
         *eax = env->cpuid_xlevel;
-        *ebx = env->cpuid_vendor1;
-        *edx = env->cpuid_vendor2;
-        *ecx = env->cpuid_vendor3;
+
+        if (cpu->vendor_cpuid_only_v2 &&
+            (IS_INTEL_CPU(env) || IS_ZHAOXIN_CPU(env))) {
+            *ebx = *ecx = *edx = 0;
+        } else {
+            *ebx = env->cpuid_vendor1;
+            *edx = env->cpuid_vendor2;
+            *ecx = env->cpuid_vendor3;
+        }
         break;
     case 0x80000001:
         *eax = env->cpuid_version;