[Qemu-devel] [PATCH 3/5] target-i386: remove vendor_override field from CPUX86State

[Igor Mammedov <imammedo@redhat.com>]

commit 8935499831312 makes cpuid return to guest host's vendor value
instead of built-in one by default if kvm_enabled() == true and allows
to override this behavior if 'vendor' is specified on -cpu command line.

But every time guest calls cpuid to get 'vendor' value, host's value is
read again and again in default case.

It complicates semantic of vendor property and makes it harder to use.

Instead of reading 'vendor' value from host every time cpuid[vendor] is
called, override 'vendor' value only once in cpu_x86_find_by_name(), when
built-in CPU model is found and if(kvm_enabled() == true).

It provides the same default semantic
 if (kvm_enabled() == true)  vendor = host's vendor
 else vendor = built-in vendor

and then later:
 if (custom vendor) vendor = custom vendor

'vendor' value is overridden when user provides it on -cpu command line,
and there isn't need in vendor_override field anymore, remove it.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
 v4:
   - rebased with "target-i386: move out CPU features initialization
     in separate func" dropped. So remove vendor_override in
     cpu_x86_register() instead.
   - replace x86cpu_vendor_words2str() with x86_cpu_vendor_words2str()
     due to renaming of the last in previous patch
---
 target-i386/cpu.c |   27 ++++++++++++---------------
 target-i386/cpu.h |    1 -
 2 files changed, 12 insertions(+), 16 deletions(-)

diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index ab80dbe..5cd7917 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -362,7 +362,6 @@ typedef struct x86_def_t {
     uint32_t kvm_features, svm_features;
     uint32_t xlevel;
     char model_id[48];
-    int vendor_override;
     /* Store the results of Centaur's CPUID instructions */
     uint32_t ext4_features;
     uint32_t xlevel2;
@@ -934,7 +933,6 @@ static void kvm_cpu_fill_host(x86_def_t *x86_cpu_def)
                 kvm_arch_get_supported_cpuid(s, 0x80000001, 0, R_ECX);
 
     cpu_x86_fill_model_id(x86_cpu_def->model_id);
-    x86_cpu_def->vendor_override = 0;
 
     /* Call Centaur's CPUID instruction. */
     if (!strncmp(x86_cpu_def->vendor, CPUID_VENDOR_VIA,
@@ -1202,7 +1200,6 @@ static void x86_cpuid_set_vendor(Object *obj, const char *value,
         env->cpuid_vendor2 |= ((uint8_t)value[i + 4]) << (8 * i);
         env->cpuid_vendor3 |= ((uint8_t)value[i + 8]) << (8 * i);
     }
-    env->cpuid_vendor_override = 1;
 }
 
 static char *x86_cpuid_get_model_id(Object *obj, Error **errp)
@@ -1288,6 +1285,18 @@ static int cpu_x86_find_by_name(x86_def_t *x86_cpu_def, const char *name)
         return -1;
     } else {
         memcpy(x86_cpu_def, def, sizeof(*def));
+        /* sysenter isn't supported on compatibility mode on AMD, syscall
+         * isn't supported in compatibility mode on Intel.
+         * Normally we advertise the actual cpu vendor, but you can override
+         * this using the 'vendor' property if you want to use KVM's
+         * sysenter/syscall emulation in compatibility mode and when doing
+         * cross vendor migration
+         */
+        if (kvm_enabled()) {
+            uint32_t  ebx = 0, ecx = 0, edx = 0;
+            host_cpuid(0, 0, NULL, &ebx, &ecx, &edx);
+            x86_cpu_vendor_words2str(x86_cpu_def->vendor, ebx, edx, ecx);
+        }
     }
 
     return 0;
@@ -1361,7 +1370,6 @@ static int cpu_x86_parse_featurestr(x86_def_t *x86_cpu_def, char *features)
                 x86_cpu_def->xlevel = numvalue;
             } else if (!strcmp(featurestr, "vendor")) {
                 pstrcpy(x86_cpu_def->vendor, sizeof(x86_cpu_def->vendor), val);
-                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);
@@ -1557,7 +1565,6 @@ int cpu_x86_register(X86CPU *cpu, const char *cpu_model)
     }
     assert(def->vendor[0]);
     object_property_set_str(OBJECT(cpu), def->vendor, "vendor", &error);
-    env->cpuid_vendor_override = def->vendor_override;
     object_property_set_int(OBJECT(cpu), def->level, "level", &error);
     object_property_set_int(OBJECT(cpu), def->family, "family", &error);
     object_property_set_int(OBJECT(cpu), def->model, "model", &error);
@@ -1629,16 +1636,6 @@ static void get_cpuid_vendor(CPUX86State *env, uint32_t *ebx,
     *ebx = env->cpuid_vendor1;
     *edx = env->cpuid_vendor2;
     *ecx = env->cpuid_vendor3;
-
-    /* sysenter isn't supported on compatibility mode on AMD, syscall
-     * isn't supported in compatibility mode on Intel.
-     * Normally we advertise the actual cpu vendor, but you can override
-     * this if you want to use KVM's sysenter/syscall emulation
-     * in compatibility mode and when doing cross vendor migration
-     */
-    if (kvm_enabled() && ! env->cpuid_vendor_override) {
-        host_cpuid(0, 0, NULL, ebx, ecx, edx);
-    }
 }
 
 void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
diff --git a/target-i386/cpu.h b/target-i386/cpu.h
index 554bd4a..53e1ea0 100644
--- a/target-i386/cpu.h
+++ b/target-i386/cpu.h
@@ -835,7 +835,6 @@ typedef struct CPUX86State {
     uint32_t cpuid_ext2_features;
     uint32_t cpuid_ext3_features;
     uint32_t cpuid_apic_id;
-    int cpuid_vendor_override;
     /* Store the results of Centaur's CPUID instructions */
     uint32_t cpuid_xlevel2;
     uint32_t cpuid_ext4_features;
-- 
1.7.1