Re: [Qemu-devel] [PATCH v2 3/5] target/i386: Add support for CPUID_8000_001E for AMD

[Moger, Babu]

> -----Original Message-----
> From: Radim Krčmář [mailto:address@hidden
> Sent: Wednesday, February 28, 2018 12:24 PM
> To: Moger, Babu <address@hidden>
> Cc: address@hidden; address@hidden; address@hidden;
> address@hidden; address@hidden; address@hidden;
> address@hidden; Hook, Gary <address@hidden>
> Subject: Re: [PATCH v2 3/5] target/i386: Add support for CPUID_8000_001E
> for AMD
> 
> 2018-02-23 21:30-0500, Babu Moger:
> > From: Stanislav Lanci <address@hidden>
> >
> > Populate threads/core_id/apic_ids/socket_id when CPUID_EXT3_TOPOEXT
> > feature is supported. This is required to support hyperthreading
> > feature on AMD CPUS. These are supported via CPUID_8000_001E
> extended
> > functions.
> >
> > Signed-off-by: Stanislav Lanci <address@hidden>
> > Signed-off-by: Babu Moger <address@hidden>
> > ---
> >  target/i386/cpu.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> >
> > diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> > index a5a480e..191e850 100644
> > --- a/target/i386/cpu.c
> > +++ b/target/i386/cpu.c
> > @@ -3666,6 +3666,14 @@ void cpu_x86_cpuid(CPUX86State *env,
> uint32_t index, uint32_t count,
> >              *edx = 0;
> >          }
> >          break;
> > +    case 0x8000001E:
> > +        if (env->features[FEAT_8000_0001_ECX] & CPUID_EXT3_TOPOEXT) {
> > +            *eax = cpu->apic_id;
> > +            *ebx = (cs->nr_threads - 1) << 8 | cpu->core_id;
> 
> Do we somewhere assert that AMD cannot have cpu->core_id > 255?
> (qemu does allow weird configurations.)

I don't see specific assert on core_id.   But, I see that qemu does not allow 
nr_cores more than 255.
Also I see that core_id is iterated based on nr_cores.  If you strongly believe 
we need to add assert here, I will add it. 
Let me know.
 
> Thanks.
> 
> > +            *ecx = cpu->socket_id;
> > +            *edx = 0;
> > +        }
> > +        break;
> >      case 0xC0000000:
> >          *eax = env->cpuid_xlevel2;
> >          *ebx = 0;
> > --
> > 1.8.3.1
> >