[PATCH] Match virtual machine processor vendor to that of the host

[Jeremy Katz <katzj-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

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Currently, kvm ends up just using the standard qemu cpu initialization.
This means that all x86_64 virtual machines appear to have an
AuthenticAMD (AMD64) processor.  This ends up causing a problem when
booting some x86_64 Linux kernels as they attempt to do AMD64 specific
initialization for things like performance counters.  Since those MSRs
aren't supported on the Intel host, the virtual machine is halted.

The attached patch makes it so that we check the actual cpu type of the
host and then provide the same cpu type for the virtual machine.

Jeremy

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Index: qemu/exec-all.h
===================================================================
--- qemu/exec-all.h	(revision 4142)
+++ qemu/exec-all.h	(working copy)
@@ -603,3 +603,7 @@
 }
 
 #endif
+
+#ifdef USE_KVM
+#include "qemu-kvm.h"
+#endif
--- qemu/target-i386/helper2.c	(revision 4142)
+++ qemu/target-i386/helper2.c	(working copy)
@@ -141,6 +141,9 @@
 #ifdef USE_KQEMU
     kqemu_init(env);
 #endif
+#ifdef USE_KVM
+    kvm_cpu_init(env);
+#endif
     return env;
 }
 
--- qemu/qemu-kvm.c	(revision 4142)
+++ qemu/qemu-kvm.c	(working copy)
@@ -590,6 +590,56 @@
     .io_window = kvm_io_window,
 };
 
+static inline unsigned int cpuid_ebx(unsigned int op)
+{
+    unsigned int eax, ebx;
+    __asm__ volatile
+	("movl %%ebx, %%esi\n\t"
+         "cpuid\n\t"
+         "xchgl %%ebx, %%esi"
+         : "=a" (eax), "=S" (ebx)
+         : "0" (op));
+    return ebx;
+}
+
+static void kvm_update_cpuid(CPUState *env)
+{
+    int family, model, stepping;
+
+    /* we need to differentiate intel vs amd processors here.  
+     * FIXME: should match more cpuid capabilities here */
+    switch (cpuid_ebx(0)) {
+    case 0x756e6547: /* Intel */
+        env->cpuid_vendor1 = 0x756e6547; /* "Genu" */
+        env->cpuid_vendor2 = 0x49656e69; /* "ineI" */
+        env->cpuid_vendor3 = 0x6c65746e; /* "ntel" */
+        family = 6;
+        model = 15;
+        stepping = 3;
+        break;
+    case 0x68747541: /* AMD */
+        env->cpuid_vendor1 = 0x68747541; /* "Auth" */
+        env->cpuid_vendor2 = 0x69746e65; /* "enti" */
+        env->cpuid_vendor3 = 0x444d4163; /* "cAMD" */
+        family = 6;
+        model = 2;
+        stepping = 3;
+        break;
+    default:
+        /* we don't know what it is, just return */
+        return;
+        break;
+    }
+
+    env->cpuid_version = (family << 8) | (model << 4) | stepping;
+}
+
+int kvm_cpu_init(CPUState *env)
+{
+    kvm_update_cpuid(env);
+    return 0;
+}
+
 int kvm_qemu_init()
 {
     /* Try to initialize kvm */
 
Index: qemu/qemu-kvm.h
===================================================================
--- qemu/qemu-kvm.h	(revision 4142)
+++ qemu/qemu-kvm.h	(working copy)
@@ -10,4 +10,6 @@
 int kvm_cpu_exec(CPUState *env);
 int kvm_update_debugger(CPUState *env);
 
+int kvm_cpu_init(CPUState *env);
+
 #endif

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