Re: [Qemu-devel] [PATCH v2 09/15] target-i386: Add property getter for CPU model

[Andreas Färber]

Am 24.04.2012 18:36, schrieb Michael Roth:
> On Tue, Apr 24, 2012 at 11:33:35AM +0200, Andreas Färber wrote:
>> Signed-off-by: Andreas Färber <address@hidden>
>> ---
>>  target-i386/cpu.c |   14 +++++++++++++-
>>  1 files changed, 13 insertions(+), 1 deletions(-)
>>
>> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
>> index 9479717..643289f 100644
>> --- a/target-i386/cpu.c
>> +++ b/target-i386/cpu.c
>> @@ -640,6 +640,18 @@ static void x86_cpuid_version_set_family(Object *obj, 
>> Visitor *v, void *opaque,
>>      }
>>  }
>>  
>> +static void x86_cpuid_version_get_model(Object *obj, Visitor *v, void 
>> *opaque,
>> +                                        const char *name, Error **errp)
>> +{
>> +    X86CPU *cpu = X86_CPU(obj);
>> +    CPUX86State *env = &cpu->env;
>> +    int64_t value;
>> +
>> +    value = (env->cpuid_version >> 4) & 0xf;
>> +    value |= ((env->cpuid_version >> 16) & 0xf) << 4;
>> +    visit_type_int(v, &value, name, errp);
>> +}
>> +
> 
> Reviewed-by: Michael Roth <address@hidden>
> 
> Just a note though,
> 
> The setter code does:
> 
>     env->cpuid_version &= ~0xf00f0;
>     env->cpuid_version |= ((model & 0xf) << 4) | ((model >> 4) << 16);
> 
> So as a result I think there's a potential for the getter to not report bits
> that were incorrectly set and exposed to the guest, since we mask off
> bits outside the valid range in your code. But that would be a bug in the
> setter code/cpudef of course and could be addressed outside this series.

Sorry, I don't follow... Are you missing the if (value > 0xff) return;
path in the setter (05/15)? Or do you have example numbers that break?

I did it in two lines due to the 80-char limit. And env->cpuid_version
contains more than just the model so we must mask in the getter.

Are you saying the 16-bit limit is wrong and there should be a third
nibble somewhere?

Andreas

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