Instead of storing the raw CPUID data in CPUX86State and having
to convert the data back and forth on the QOM getter/setter, use
a simple static string property, and calculate CPUID data inside
cpu_x86_cpuid().

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
---
 target/i386/cpu.h |  2 +-
 target/i386/cpu.c | 62 ++++++++++++++++---------------------------------------
 2 files changed, 19 insertions(+), 45 deletions(-)

diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 7a228af..f56a3ea 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -1151,7 +1151,7 @@ typedef struct CPUX86State {
     FeatureWordArray features;
     /* Features that were explicitly enabled/disabled */
     FeatureWordArray user_features;
-    uint32_t cpuid_model[12];
+    char *model_id;
 
     /* MTRRs */
     uint64_t mtrr_fixed[11];
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index c571772..30b704c 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -1828,43 +1828,6 @@ static void x86_cpuid_set_vendor(Object *obj, const char *value,
     }
 }
 
-static char *x86_cpuid_get_model_id(Object *obj, Error **errp)
-{
-    X86CPU *cpu = X86_CPU(obj);
-    CPUX86State *env = &cpu->env;
-    char *value;
-    int i;
-
-    value = g_malloc(48 + 1);
-    for (i = 0; i < 48; i++) {
-        value[i] = env->cpuid_model[i >> 2] >> (8 * (i & 3));
-    }
-    value[48] = '\0';
-    return value;
-}
-
-static void x86_cpuid_set_model_id(Object *obj, const char *model_id,
-                                   Error **errp)
-{
-    X86CPU *cpu = X86_CPU(obj);
-    CPUX86State *env = &cpu->env;
-    int c, len, i;
-
-    if (model_id == NULL) {
-        model_id = "";
-    }
-    len = strlen(model_id);
-    memset(env->cpuid_model, 0, 48);
-    for (i = 0; i < 48; i++) {
-        if (i >= len) {
-            c = '\0';
-        } else {
-            c = (uint8_t)model_id[i];
-        }
-        env->cpuid_model[i >> 2] |= c << (8 * (i & 3));
-    }
-}
-
 static void x86_cpuid_get_tsc_freq(Object *obj, Visitor *v, const char *name,
                                    void *opaque, Error **errp)
 {
@@ -2899,10 +2862,23 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
     case 0x80000002:
     case 0x80000003:
     case 0x80000004:
-        *eax = env->cpuid_model[(index - 0x80000002) * 4 + 0];
-        *ebx = env->cpuid_model[(index - 0x80000002) * 4 + 1];
-        *ecx = env->cpuid_model[(index - 0x80000002) * 4 + 2];
-        *edx = env->cpuid_model[(index - 0x80000002) * 4 + 3];
+        {
+            int i;
+            int len = strlen(env->model_id);
+            uint32_t model[4] = { 0, 0, 0, 0 };
+
+            for (i = 0; i < 16; i++) {
+                int p = (index - 0x80000002) * 16 + i;
+                if (p >= len) {
+                    continue;
+                }
+                model[i >> 2] |= ((uint8_t)env->model_id[p]) << (8 * (i & 3));
+            }
+            *eax = model[0];
+            *ebx = model[1];
+            *ecx = model[2];
+            *edx = model[3];
+        }
         break;
     case 0x80000005:
         /* cache info (L1 cache) */
@@ -3868,9 +3844,6 @@ static void x86_cpu_initfn(Object *obj)
     object_property_add_str(obj, "vendor",
                             x86_cpuid_get_vendor,
                             x86_cpuid_set_vendor, NULL);
-    object_property_add_str(obj, "model-id",
-                            x86_cpuid_get_model_id,
-                            x86_cpuid_set_model_id, NULL);
     object_property_add(obj, "tsc-frequency", "int",
                         x86_cpuid_get_tsc_freq,
                         x86_cpuid_set_tsc_freq, NULL, NULL, NULL);
@@ -4004,6 +3977,7 @@ static Property x86_cpu_properties[] = {
     DEFINE_PROP_UINT32("phys-bits", X86CPU, phys_bits, 0),
     DEFINE_PROP_BOOL("host-phys-bits", X86CPU, host_phys_bits, false),
     DEFINE_PROP_BOOL("fill-mtrr-mask", X86CPU, fill_mtrr_mask, true),
+    DEFINE_PROP_STRING("model-id", X86CPU, env.model_id),
     DEFINE_PROP_UINT32("level", X86CPU, env.cpuid_level, UINT32_MAX),
     DEFINE_PROP_UINT32("xlevel", X86CPU, env.cpuid_xlevel, UINT32_MAX),
     DEFINE_PROP_UINT32("xlevel2", X86CPU, env.cpuid_xlevel2, UINT32_MAX),
-- 
2.9.4

On Wed, 12 Jul 2017 13:20:55 -0300
Eduardo Habkost <ehabkost@redhat.com> wrote:

> Instead of storing the raw CPUID data in CPUX86State and having
> to convert the data back and forth on the QOM getter/setter, use
> a simple static string property, and calculate CPUID data inside
> cpu_x86_cpuid().
wouldn't this slow down 'cpuid' instruction execution,
especially in tcg mode?

Why do you need this patch except of nice code reduction it gives?

> 
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
>  target/i386/cpu.h |  2 +-
>  target/i386/cpu.c | 62 ++++++++++++++++---------------------------------------
>  2 files changed, 19 insertions(+), 45 deletions(-)
> 
> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> index 7a228af..f56a3ea 100644
> --- a/target/i386/cpu.h
> +++ b/target/i386/cpu.h
> @@ -1151,7 +1151,7 @@ typedef struct CPUX86State {
>      FeatureWordArray features;
>      /* Features that were explicitly enabled/disabled */
>      FeatureWordArray user_features;
> -    uint32_t cpuid_model[12];
> +    char *model_id;
>  
>      /* MTRRs */
>      uint64_t mtrr_fixed[11];
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index c571772..30b704c 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -1828,43 +1828,6 @@ static void x86_cpuid_set_vendor(Object *obj, const char *value,
>      }
>  }
>  
> -static char *x86_cpuid_get_model_id(Object *obj, Error **errp)
> -{
> -    X86CPU *cpu = X86_CPU(obj);
> -    CPUX86State *env = &cpu->env;
> -    char *value;
> -    int i;
> -
> -    value = g_malloc(48 + 1);
> -    for (i = 0; i < 48; i++) {
> -        value[i] = env->cpuid_model[i >> 2] >> (8 * (i & 3));
> -    }
> -    value[48] = '\0';
> -    return value;
> -}
> -
> -static void x86_cpuid_set_model_id(Object *obj, const char *model_id,
> -                                   Error **errp)
> -{
> -    X86CPU *cpu = X86_CPU(obj);
> -    CPUX86State *env = &cpu->env;
> -    int c, len, i;
> -
> -    if (model_id == NULL) {
> -        model_id = "";
> -    }
> -    len = strlen(model_id);
> -    memset(env->cpuid_model, 0, 48);
> -    for (i = 0; i < 48; i++) {
> -        if (i >= len) {
> -            c = '\0';
> -        } else {
> -            c = (uint8_t)model_id[i];
> -        }
> -        env->cpuid_model[i >> 2] |= c << (8 * (i & 3));
> -    }
> -}
> -
>  static void x86_cpuid_get_tsc_freq(Object *obj, Visitor *v, const char *name,
>                                     void *opaque, Error **errp)
>  {
> @@ -2899,10 +2862,23 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
>      case 0x80000002:
>      case 0x80000003:
>      case 0x80000004:
> -        *eax = env->cpuid_model[(index - 0x80000002) * 4 + 0];
> -        *ebx = env->cpuid_model[(index - 0x80000002) * 4 + 1];
> -        *ecx = env->cpuid_model[(index - 0x80000002) * 4 + 2];
> -        *edx = env->cpuid_model[(index - 0x80000002) * 4 + 3];
> +        {
> +            int i;
> +            int len = strlen(env->model_id);
> +            uint32_t model[4] = { 0, 0, 0, 0 };
> +
> +            for (i = 0; i < 16; i++) {
> +                int p = (index - 0x80000002) * 16 + i;
> +                if (p >= len) {
> +                    continue;
> +                }
> +                model[i >> 2] |= ((uint8_t)env->model_id[p]) << (8 * (i & 3));
> +            }
> +            *eax = model[0];
> +            *ebx = model[1];
> +            *ecx = model[2];
> +            *edx = model[3];
> +        }
>          break;
>      case 0x80000005:
>          /* cache info (L1 cache) */
> @@ -3868,9 +3844,6 @@ static void x86_cpu_initfn(Object *obj)
>      object_property_add_str(obj, "vendor",
>                              x86_cpuid_get_vendor,
>                              x86_cpuid_set_vendor, NULL);
> -    object_property_add_str(obj, "model-id",
> -                            x86_cpuid_get_model_id,
> -                            x86_cpuid_set_model_id, NULL);
>      object_property_add(obj, "tsc-frequency", "int",
>                          x86_cpuid_get_tsc_freq,
>                          x86_cpuid_set_tsc_freq, NULL, NULL, NULL);
> @@ -4004,6 +3977,7 @@ static Property x86_cpu_properties[] = {
>      DEFINE_PROP_UINT32("phys-bits", X86CPU, phys_bits, 0),
>      DEFINE_PROP_BOOL("host-phys-bits", X86CPU, host_phys_bits, false),
>      DEFINE_PROP_BOOL("fill-mtrr-mask", X86CPU, fill_mtrr_mask, true),
> +    DEFINE_PROP_STRING("model-id", X86CPU, env.model_id),
>      DEFINE_PROP_UINT32("level", X86CPU, env.cpuid_level, UINT32_MAX),
>      DEFINE_PROP_UINT32("xlevel", X86CPU, env.cpuid_xlevel, UINT32_MAX),
>      DEFINE_PROP_UINT32("xlevel2", X86CPU, env.cpuid_xlevel2, UINT32_MAX),

On Mon, Jul 17, 2017 at 02:03:43PM +0200, Igor Mammedov wrote:
> On Wed, 12 Jul 2017 13:20:55 -0300
> Eduardo Habkost <ehabkost@redhat.com> wrote:
> 
> > Instead of storing the raw CPUID data in CPUX86State and having
> > to convert the data back and forth on the QOM getter/setter, use
> > a simple static string property, and calculate CPUID data inside
> > cpu_x86_cpuid().
> wouldn't this slow down 'cpuid' instruction execution,
> especially in tcg mode?

It may add a few additional CPU cycles, but I really doubt we can
find a workload where CPUID speed has measurable impact.  See,
for example, how expensive the kernel KVM CPUID code
(kvm_cpuid(), kvm_find_cpuid_entry()) is.

Richard, what do you think?


> 
> Why do you need this patch except of nice code reduction it gives?

It's just for code reduction, and it is not needed for this
series, if I recall correctly.  It can be included later, if
necessary.

> 
> > 
> > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> > ---
> >  target/i386/cpu.h |  2 +-
> >  target/i386/cpu.c | 62 ++++++++++++++++---------------------------------------
> >  2 files changed, 19 insertions(+), 45 deletions(-)
> > 
> > diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> > index 7a228af..f56a3ea 100644
> > --- a/target/i386/cpu.h
> > +++ b/target/i386/cpu.h
> > @@ -1151,7 +1151,7 @@ typedef struct CPUX86State {
> >      FeatureWordArray features;
> >      /* Features that were explicitly enabled/disabled */
> >      FeatureWordArray user_features;
> > -    uint32_t cpuid_model[12];
> > +    char *model_id;
> >  
> >      /* MTRRs */
> >      uint64_t mtrr_fixed[11];
> > diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> > index c571772..30b704c 100644
> > --- a/target/i386/cpu.c
> > +++ b/target/i386/cpu.c
> > @@ -1828,43 +1828,6 @@ static void x86_cpuid_set_vendor(Object *obj, const char *value,
> >      }
> >  }
> >  
> > -static char *x86_cpuid_get_model_id(Object *obj, Error **errp)
> > -{
> > -    X86CPU *cpu = X86_CPU(obj);
> > -    CPUX86State *env = &cpu->env;
> > -    char *value;
> > -    int i;
> > -
> > -    value = g_malloc(48 + 1);
> > -    for (i = 0; i < 48; i++) {
> > -        value[i] = env->cpuid_model[i >> 2] >> (8 * (i & 3));
> > -    }
> > -    value[48] = '\0';
> > -    return value;
> > -}
> > -
> > -static void x86_cpuid_set_model_id(Object *obj, const char *model_id,
> > -                                   Error **errp)
> > -{
> > -    X86CPU *cpu = X86_CPU(obj);
> > -    CPUX86State *env = &cpu->env;
> > -    int c, len, i;
> > -
> > -    if (model_id == NULL) {
> > -        model_id = "";
> > -    }
> > -    len = strlen(model_id);
> > -    memset(env->cpuid_model, 0, 48);
> > -    for (i = 0; i < 48; i++) {
> > -        if (i >= len) {
> > -            c = '\0';
> > -        } else {
> > -            c = (uint8_t)model_id[i];
> > -        }
> > -        env->cpuid_model[i >> 2] |= c << (8 * (i & 3));
> > -    }
> > -}
> > -
> >  static void x86_cpuid_get_tsc_freq(Object *obj, Visitor *v, const char *name,
> >                                     void *opaque, Error **errp)
> >  {
> > @@ -2899,10 +2862,23 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
> >      case 0x80000002:
> >      case 0x80000003:
> >      case 0x80000004:
> > -        *eax = env->cpuid_model[(index - 0x80000002) * 4 + 0];
> > -        *ebx = env->cpuid_model[(index - 0x80000002) * 4 + 1];
> > -        *ecx = env->cpuid_model[(index - 0x80000002) * 4 + 2];
> > -        *edx = env->cpuid_model[(index - 0x80000002) * 4 + 3];
> > +        {
> > +            int i;
> > +            int len = strlen(env->model_id);
> > +            uint32_t model[4] = { 0, 0, 0, 0 };
> > +
> > +            for (i = 0; i < 16; i++) {
> > +                int p = (index - 0x80000002) * 16 + i;
> > +                if (p >= len) {
> > +                    continue;
> > +                }
> > +                model[i >> 2] |= ((uint8_t)env->model_id[p]) << (8 * (i & 3));
> > +            }
> > +            *eax = model[0];
> > +            *ebx = model[1];
> > +            *ecx = model[2];
> > +            *edx = model[3];
> > +        }
> >          break;
> >      case 0x80000005:
> >          /* cache info (L1 cache) */
> > @@ -3868,9 +3844,6 @@ static void x86_cpu_initfn(Object *obj)
> >      object_property_add_str(obj, "vendor",
> >                              x86_cpuid_get_vendor,
> >                              x86_cpuid_set_vendor, NULL);
> > -    object_property_add_str(obj, "model-id",
> > -                            x86_cpuid_get_model_id,
> > -                            x86_cpuid_set_model_id, NULL);
> >      object_property_add(obj, "tsc-frequency", "int",
> >                          x86_cpuid_get_tsc_freq,
> >                          x86_cpuid_set_tsc_freq, NULL, NULL, NULL);
> > @@ -4004,6 +3977,7 @@ static Property x86_cpu_properties[] = {
> >      DEFINE_PROP_UINT32("phys-bits", X86CPU, phys_bits, 0),
> >      DEFINE_PROP_BOOL("host-phys-bits", X86CPU, host_phys_bits, false),
> >      DEFINE_PROP_BOOL("fill-mtrr-mask", X86CPU, fill_mtrr_mask, true),
> > +    DEFINE_PROP_STRING("model-id", X86CPU, env.model_id),
> >      DEFINE_PROP_UINT32("level", X86CPU, env.cpuid_level, UINT32_MAX),
> >      DEFINE_PROP_UINT32("xlevel", X86CPU, env.cpuid_xlevel, UINT32_MAX),
> >      DEFINE_PROP_UINT32("xlevel2", X86CPU, env.cpuid_xlevel2, UINT32_MAX),
> 

-- 
Eduardo

On Mon, 17 Jul 2017 14:18:27 -0300
Eduardo Habkost <ehabkost@redhat.com> wrote:

> On Mon, Jul 17, 2017 at 02:03:43PM +0200, Igor Mammedov wrote:
> > On Wed, 12 Jul 2017 13:20:55 -0300
> > Eduardo Habkost <ehabkost@redhat.com> wrote:
> >   
> > > Instead of storing the raw CPUID data in CPUX86State and having
> > > to convert the data back and forth on the QOM getter/setter, use
> > > a simple static string property, and calculate CPUID data inside
> > > cpu_x86_cpuid().  
> > wouldn't this slow down 'cpuid' instruction execution,
> > especially in tcg mode?  
> 
> It may add a few additional CPU cycles, but I really doubt we can
> find a workload where CPUID speed has measurable impact.  See,
> for example, how expensive the kernel KVM CPUID code
> (kvm_cpuid(), kvm_find_cpuid_entry()) is.
I don't expect that it would affect KVM, but for TCG any instruction
execution is 'fast' path, so I'd leave current cpu_x86_cpuid()
not to loose those few cycles, it's not worth sacrifice for the sake of cleanup.

> 
> Richard, what do you think?
> 
> 
> > 
> > Why do you need this patch except of nice code reduction it gives?  
> 
> It's just for code reduction, and it is not needed for this
> series, if I recall correctly.  It can be included later, if
> necessary.
> 
> >   
> > > 
> > > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> > > ---
> > >  target/i386/cpu.h |  2 +-
> > >  target/i386/cpu.c | 62 ++++++++++++++++---------------------------------------
> > >  2 files changed, 19 insertions(+), 45 deletions(-)
> > > 
> > > diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> > > index 7a228af..f56a3ea 100644
> > > --- a/target/i386/cpu.h
> > > +++ b/target/i386/cpu.h
> > > @@ -1151,7 +1151,7 @@ typedef struct CPUX86State {
> > >      FeatureWordArray features;
> > >      /* Features that were explicitly enabled/disabled */
> > >      FeatureWordArray user_features;
> > > -    uint32_t cpuid_model[12];
> > > +    char *model_id;
> > >  
> > >      /* MTRRs */
> > >      uint64_t mtrr_fixed[11];
> > > diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> > > index c571772..30b704c 100644
> > > --- a/target/i386/cpu.c
> > > +++ b/target/i386/cpu.c
> > > @@ -1828,43 +1828,6 @@ static void x86_cpuid_set_vendor(Object *obj, const char *value,
> > >      }
> > >  }
> > >  
> > > -static char *x86_cpuid_get_model_id(Object *obj, Error **errp)
> > > -{
> > > -    X86CPU *cpu = X86_CPU(obj);
> > > -    CPUX86State *env = &cpu->env;
> > > -    char *value;
> > > -    int i;
> > > -
> > > -    value = g_malloc(48 + 1);
> > > -    for (i = 0; i < 48; i++) {
> > > -        value[i] = env->cpuid_model[i >> 2] >> (8 * (i & 3));
> > > -    }
> > > -    value[48] = '\0';
> > > -    return value;
> > > -}
> > > -
> > > -static void x86_cpuid_set_model_id(Object *obj, const char *model_id,
> > > -                                   Error **errp)
> > > -{
> > > -    X86CPU *cpu = X86_CPU(obj);
> > > -    CPUX86State *env = &cpu->env;
> > > -    int c, len, i;
> > > -
> > > -    if (model_id == NULL) {
> > > -        model_id = "";
> > > -    }
> > > -    len = strlen(model_id);
> > > -    memset(env->cpuid_model, 0, 48);
> > > -    for (i = 0; i < 48; i++) {
> > > -        if (i >= len) {
> > > -            c = '\0';
> > > -        } else {
> > > -            c = (uint8_t)model_id[i];
> > > -        }
> > > -        env->cpuid_model[i >> 2] |= c << (8 * (i & 3));
> > > -    }
> > > -}
> > > -
> > >  static void x86_cpuid_get_tsc_freq(Object *obj, Visitor *v, const char *name,
> > >                                     void *opaque, Error **errp)
> > >  {
> > > @@ -2899,10 +2862,23 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
> > >      case 0x80000002:
> > >      case 0x80000003:
> > >      case 0x80000004:
> > > -        *eax = env->cpuid_model[(index - 0x80000002) * 4 + 0];
> > > -        *ebx = env->cpuid_model[(index - 0x80000002) * 4 + 1];
> > > -        *ecx = env->cpuid_model[(index - 0x80000002) * 4 + 2];
> > > -        *edx = env->cpuid_model[(index - 0x80000002) * 4 + 3];
> > > +        {
> > > +            int i;
> > > +            int len = strlen(env->model_id);
> > > +            uint32_t model[4] = { 0, 0, 0, 0 };
> > > +
> > > +            for (i = 0; i < 16; i++) {
> > > +                int p = (index - 0x80000002) * 16 + i;
> > > +                if (p >= len) {
> > > +                    continue;
> > > +                }
> > > +                model[i >> 2] |= ((uint8_t)env->model_id[p]) << (8 * (i & 3));
> > > +            }
> > > +            *eax = model[0];
> > > +            *ebx = model[1];
> > > +            *ecx = model[2];
> > > +            *edx = model[3];
> > > +        }
> > >          break;
> > >      case 0x80000005:
> > >          /* cache info (L1 cache) */
> > > @@ -3868,9 +3844,6 @@ static void x86_cpu_initfn(Object *obj)
> > >      object_property_add_str(obj, "vendor",
> > >                              x86_cpuid_get_vendor,
> > >                              x86_cpuid_set_vendor, NULL);
> > > -    object_property_add_str(obj, "model-id",
> > > -                            x86_cpuid_get_model_id,
> > > -                            x86_cpuid_set_model_id, NULL);
> > >      object_property_add(obj, "tsc-frequency", "int",
> > >                          x86_cpuid_get_tsc_freq,
> > >                          x86_cpuid_set_tsc_freq, NULL, NULL, NULL);
> > > @@ -4004,6 +3977,7 @@ static Property x86_cpu_properties[] = {
> > >      DEFINE_PROP_UINT32("phys-bits", X86CPU, phys_bits, 0),
> > >      DEFINE_PROP_BOOL("host-phys-bits", X86CPU, host_phys_bits, false),
> > >      DEFINE_PROP_BOOL("fill-mtrr-mask", X86CPU, fill_mtrr_mask, true),
> > > +    DEFINE_PROP_STRING("model-id", X86CPU, env.model_id),
> > >      DEFINE_PROP_UINT32("level", X86CPU, env.cpuid_level, UINT32_MAX),
> > >      DEFINE_PROP_UINT32("xlevel", X86CPU, env.cpuid_xlevel, UINT32_MAX),
> > >      DEFINE_PROP_UINT32("xlevel2", X86CPU, env.cpuid_xlevel2, UINT32_MAX),  
> >   
> 

On 18/07/2017 13:29, Igor Mammedov wrote:
>> It may add a few additional CPU cycles, but I really doubt we can
>> find a workload where CPUID speed has measurable impact.  See,
>> for example, how expensive the kernel KVM CPUID code
>> (kvm_cpuid(), kvm_find_cpuid_entry()) is.
> 
> I don't expect that it would affect KVM, but for TCG any instruction
> execution is 'fast' path, so I'd leave current cpu_x86_cpuid()
> not to loose those few cycles, it's not worth sacrifice for the sake of cleanup.

It's not like this does a QOM property lookup or anything.  I think the
patch is a good idea.

Even simpler way to write the cpuid code:

            int base = (index - 0x80000002) * 16;
            char model[16];

            if (strnlen(env->model_id, base) < base) {
                memset(model, 0, sizeof(model));
            } else {
                strncpy(model, env->model_id + base, sizeof(model));
            }
            *eax = ldl_le_p(&model[0]);
            *ebx = ldl_le_p(&model[4]);
            *ecx = ldl_le_p(&model[8]);
            *edx = ldl_le_p(&model[12]);

Paolo

On Mon, Jul 24, 2017 at 11:11:34PM +0200, Paolo Bonzini wrote:
> On 18/07/2017 13:29, Igor Mammedov wrote:
> >> It may add a few additional CPU cycles, but I really doubt we can
> >> find a workload where CPUID speed has measurable impact.  See,
> >> for example, how expensive the kernel KVM CPUID code
> >> (kvm_cpuid(), kvm_find_cpuid_entry()) is.
> > 
> > I don't expect that it would affect KVM, but for TCG any instruction
> > execution is 'fast' path, so I'd leave current cpu_x86_cpuid()
> > not to loose those few cycles, it's not worth sacrifice for the sake of cleanup.
> 
> It's not like this does a QOM property lookup or anything.  I think the
> patch is a good idea.
> 
> Even simpler way to write the cpuid code:
> 
>             int base = (index - 0x80000002) * 16;
>             char model[16];
> 
>             if (strnlen(env->model_id, base) < base) {
>                 memset(model, 0, sizeof(model));
>             } else {
>                 strncpy(model, env->model_id + base, sizeof(model));
>             }
>             *eax = ldl_le_p(&model[0]);
>             *ebx = ldl_le_p(&model[4]);
>             *ecx = ldl_le_p(&model[8]);
>             *edx = ldl_le_p(&model[12]);

Neat.  I will use it in v2.  Thanks!

-- 
Eduardo