[PATCH] KVM-userspace: allow CPUID vendor override

[PATCH] KVM-userspace: allow CPUID vendor override

[Andre Przywara]

Hi,

currently KVM always propagates the host CPU vendor ID to the guest. This
patch allows to override this behavior by explicitly specifying a vendor ID
with -cpu qemu64,vendor=KVMKVMKVMKVM. This proved to be useful for cross
vendor migration tests.

Regards,
Andre.

Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany
Tel: +49 351 277-84917
****to satisfy European Law for business letters:
Advanced Micro Devices GmbH
Karl-Hammerschmidt-Str. 34, 85609 Dornach b. Muenchen
Geschaeftsfuehrer: Jochen Polster; Thomas M. McCoy; Giuliano Meroni
Sitz: Dornach, Gemeinde Aschheim, Landkreis Muenchen
Registergericht Muenchen, HRB Nr. 43632


Signed-off-by: Andre Przywara <andre.przywara@amd.com>
---
 qemu/target-i386/cpu.h    |    1 +
 qemu/target-i386/helper.c |    5 ++++-
 2 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/qemu/target-i386/cpu.h b/qemu/target-i386/cpu.h
index 944e386..d83d62b 100644
--- a/qemu/target-i386/cpu.h
+++ b/qemu/target-i386/cpu.h
@@ -628,6 +628,7 @@ typedef struct CPUX86State {
     uint32_t cpuid_ext2_features;
     uint32_t cpuid_ext3_features;
     uint32_t cpuid_apic_id;
+    uint32_t cpuid_vendor_override;
 
 #ifdef USE_KQEMU
     int kqemu_enabled;
diff --git a/qemu/target-i386/helper.c b/qemu/target-i386/helper.c
index cda0390..7dbe36b 100644
--- a/qemu/target-i386/helper.c
+++ b/qemu/target-i386/helper.c
@@ -103,6 +103,7 @@ typedef struct x86_def_t {
     uint32_t features, ext_features, ext2_features, ext3_features;
     uint32_t xlevel;
     char model_id[48];
+    int vendor_override;
 } x86_def_t;
 
 #define I486_FEATURES (CPUID_FP87 | CPUID_VME | CPUID_PSE)
@@ -335,6 +336,7 @@ static int cpu_x86_find_by_name(x86_def_t *x86_cpu_def, const char *cpu_model)
                     x86_cpu_def->vendor2 |= ((uint8_t)val[i + 4]) << (8 * i);
                     x86_cpu_def->vendor3 |= ((uint8_t)val[i + 8]) << (8 * i);
                 }
+                x86_cpu_def->vendor_override = 1;
             } else if (!strcmp(featurestr, "model_id")) {
                 pstrcpy(x86_cpu_def->model_id, sizeof(x86_cpu_def->model_id),
                         val);
@@ -387,6 +389,7 @@ static int cpu_x86_register (CPUX86State *env, const char *cpu_model)
         env->cpuid_vendor2 = CPUID_VENDOR_INTEL_2;
         env->cpuid_vendor3 = CPUID_VENDOR_INTEL_3;
     }
+    env->cpuid_vendor_override = def->vendor_override;
     env->cpuid_level = def->level;
     if (def->family > 0x0f)
         env->cpuid_version = 0xf00 | ((def->family - 0x0f) << 20);
@@ -1435,7 +1438,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index,
          * isn't supported in compatibility mode on Intel.  so advertise the
          * actuall cpu, and say goodbye to migration between different vendors
          * is you use compatibility mode. */
-        if (kvm_enabled())
+        if (kvm_enabled() && ! env->cpuid_vendor_override)
             host_cpuid(0, NULL, ebx, ecx, edx);
         break;
     case 1:
-- 
1.5.2.2