On Fri, Jan 11, 2013 at 03:10:20AM +0100, Igor Mammedov wrote:
> 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
>
How do you plan to make this work when the vendor string for each model
gets represented using a default defined at class_init-time[1]? When we do
that, we wouldn't be able to differentiate the built/predefined vendor
value (used for TCG only) and the user-defined vendor value (that would
be set in KVM mode too).
[1] AFAIU, class_init would never be able to check kvm_enabled(), by
design, because it may run before anything is configured (even the
choice to enable/disable KVM).
Maybe we can later add a "tcg-vendor" property, that would override the
vendor only if in TCG mode. Then the predefined CPU models could have a
"tcg-vendor" default set, and no "vendor" default set, to emulate the
current behavior.
> '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 <imamm...@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 0b4fa57..4250c77 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 (!strcmp(x86_cpu_def->vendor, CPUID_VENDOR_VIA)) {
> @@ -1201,7 +1199,6 @@ 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)
> @@ -1287,6 +1284,18 @@ 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;
> @@ -1358,7 +1367,6 @@ 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);
> @@ -1554,7 +1562,6 @@ 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);
> @@ -1626,16 +1633,6 @@ 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 983aab1..8bb5a58 100644
> --- a/target-i386/cpu.h
> +++ b/target-i386/cpu.h
> @@ -829,7 +829,6 @@ 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
>
--
Eduardo
