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

[Michael Roth]

On Tue, Apr 24, 2012 at 06:50:28PM +0200, Andreas Färber wrote:
> 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?

Sorry, you're right, I missed the range check you added in 05/15. Looks
good.

> 
> 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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