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Re: [Qemu-devel] [PATCH 13/20] target-i386: remove vendor_override field
From: |
Eduardo Habkost |
Subject: |
Re: [Qemu-devel] [PATCH 13/20] target-i386: remove vendor_override field from CPUX86State |
Date: |
Thu, 20 Dec 2012 10:48:08 -0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Thu, Dec 20, 2012 at 01:16:31AM +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,
> due to split brain syndrome, lets simplify it.
>
> 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 <address@hidden>
> ---
> target-i386/cpu.c | 20 +++++---------------
> target-i386/cpu.h | 1 -
> 2 files changed, 5 insertions(+), 16 deletions(-)
>
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index a96aa33..a12d938 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -284,7 +284,6 @@ 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;
> @@ -865,7 +864,6 @@ 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;
>
It's funny how x86_def_t _never_ has vendor_override set to true. The
field was completely pointless.
> /* Call Centaur's CPUID instruction. */
> if (!strcmp(x86_cpu_def->vendor, CPUID_VENDOR_VIA)) {
> @@ -1117,7 +1115,6 @@ 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)
> @@ -1194,7 +1191,6 @@ static void cpudef_2_x86_cpu(X86CPU *cpu, x86_def_t
> *def, Error **errp)
>
> assert(def->vendor[0]);
> object_property_set_str(OBJECT(cpu), def->vendor, "vendor", errp);
> - env->cpuid_vendor_override = def->vendor_override;
> object_property_set_int(OBJECT(cpu), def->level, "level", errp);
> object_property_set_int(OBJECT(cpu), def->family, "family", errp);
> object_property_set_int(OBJECT(cpu), def->model, "model", errp);
> @@ -1231,6 +1227,11 @@ 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));
Could you keep the old comment explaining the reason for the KVM
behavior, here?
/* 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
*/
(I suggest replacing "you can override this" with "you can override this
using the 'vendor' property").
The rest of the patch looks good to me.
> + if (kvm_enabled()) {
> + uint32_t ebx = 0, ecx = 0, edx = 0;
> + host_cpuid(0, 0, NULL, &ebx, &ecx, &edx);
> + x86cpu_vendor_words2str(x86_cpu_def->vendor, ebx, edx, ecx);
> + }
I like the fact that you are doing this as early as possible (even
before cpudef_2_x86_cpu() is called), making it easy to move the logic
to class_init.
> }
>
> return 0;
> @@ -1331,7 +1332,6 @@ 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);
> @@ -1582,16 +1582,6 @@ 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 fbbe730..a15a09e 100644
> --- a/target-i386/cpu.h
> +++ b/target-i386/cpu.h
> @@ -812,7 +812,6 @@ 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;
> --
> 1.7.11.7
>
--
Eduardo
- Re: [Qemu-devel] [PATCH 10/20] target-i386: prepare cpu_x86_parse_featurestr() to return a set of key, value property pairs, (continued)
[Qemu-devel] [PATCH 04/20] target-i386: setting default 'vendor' is obsolete, remove it, Igor Mammedov, 2012/12/17
[Qemu-devel] [PATCH 12/20] target-i386: replace uint32_t vendor fields by vendor string in x86_def_t, Igor Mammedov, 2012/12/17
[Qemu-devel] [PATCH 18/20] target-i386: set custom 'stepping' without intermediate x86_def_t, Igor Mammedov, 2012/12/17
[Qemu-devel] [PATCH 17/20] target-i386: set custom 'model-id' without intermediate x86_def_t, Igor Mammedov, 2012/12/17
[Qemu-devel] [PATCH 19/20] target-i386: set custom 'model' without intermediate x86_def_t, Igor Mammedov, 2012/12/17
[Qemu-devel] [PATCH 16/20] target-i386: set custom 'level' without intermediate x86_def_t, Igor Mammedov, 2012/12/17
[Qemu-devel] [PATCH 20/20] target-i386: set custom 'family' without intermediate x86_def_t, Igor Mammedov, 2012/12/17
[Qemu-devel] [PATCH 15/20] target-i386: set custom 'xlevel' without intermediate x86_def_t, Igor Mammedov, 2012/12/17