target/i386: drop AMD machine check bits from Intel CPUID

The recent addition of the SUCCOR bit to kvm_arch_get_supported_cpuid()
causes the bit to be visible when "-cpu host" VMs are started on Intel
processors.

While this should in principle be harmless, it's not tidy and we don't
even know for sure that it doesn't cause any guest OS to take unexpected
paths.  Since x86_cpu_get_supported_feature_word() can return different
different values depending on the guest, adjust it to hide the SUCCOR
bit if the guest has non-AMD vendor.

Suggested-by: Xiaoyao Li <xiaoyao.li@intel.com>
Cc: John Allen <john.allen@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 4364cb0f8e3eea5f289da7f9c60fa6a692bbc818..5e5bf71702c34cab3868df91a7e3d0270f44ece1 100644 (file)
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -6039,6 +6039,7 @@ uint64_t x86_cpu_get_supported_feature_word(X86CPU *cpu, FeatureWord w)
 {
     FeatureWordInfo *wi = &feature_word_info[w];
     uint64_t r = 0;
+    uint32_t unavail = 0;
 
     if (kvm_enabled()) {
         switch (wi->type) {
@@ -6064,19 +6065,33 @@ uint64_t x86_cpu_get_supported_feature_word(X86CPU *cpu, FeatureWord w)
     } else {
         return ~0;
     }
+
+    switch (w) {
 #ifndef TARGET_X86_64
-    if (w == FEAT_8000_0001_EDX) {
+    case FEAT_8000_0001_EDX:
         /*
          * 32-bit TCG can emulate 64-bit compatibility mode.  If there is no
          * way for userspace to get out of its 32-bit jail, we can leave
          * the LM bit set.
          */
-        uint32_t unavail = tcg_enabled()
+        unavail = tcg_enabled()
             ? CPUID_EXT2_LM & ~CPUID_EXT2_KERNEL_FEATURES
             : CPUID_EXT2_LM;
-        r &= ~unavail;
-    }
+        break;
 #endif
+
+    case FEAT_8000_0007_EBX:
+        if (cpu && !IS_AMD_CPU(&cpu->env)) {
+            /* Disable AMD machine check architecture for Intel CPU.  */
+            unavail = ~0;
+        }
+        break;
+
+    default:
+        break;
+    }
+
+    r &= ~unavail;
     if (cpu && cpu->migratable) {
         r &= x86_cpu_get_migratable_flags(w);
     }