Re: [PATCH v7 7/9] i386: Add support for CPUID_8000_001E for AMD

[Eduardo Habkost <ehabkost@redhat.com>]

On Tue, May 08, 2018 at 03:02:07PM +0000, Moger, Babu wrote:
> 
> > -----Original Message-----
> > From: Eduardo Habkost [mailto:ehabkost@redhat.com]
> > Sent: Tuesday, May 8, 2018 9:17 AM
> > To: Moger, Babu <Babu.Moger@amd.com>
> > Cc: mst@redhat.com; marcel@redhat.com; pbonzini@redhat.com;
> > rth@twiddle.net; mtosatti@redhat.com; geoff@hostfission.com;
> > kash@tripleback.net; qemu-devel@nongnu.org; kvm@vger.kernel.org
> > Subject: Re: [Qemu-devel] [PATCH v7 7/9] i386: Add support for
> > CPUID_8000_001E for AMD
> > 
> > On Mon, May 07, 2018 at 11:44:31PM +0000, Moger, Babu wrote:
> > [...]
> > > > > +
> > > > >  /*
> > > > >   * Encode cache info for CPUID[0x80000006].ECX and
> > > > CPUID[0x80000006].EDX
> > > > >   * @l3 can be NULL.
> > > > > @@ -4105,6 +4111,14 @@ void cpu_x86_cpuid(CPUX86State *env,
> > > > uint32_t index, uint32_t count,
> > > > >              break;
> > > > >          }
> > > > >          break;
> > > > > +    case 0x8000001E:
> > > > > +        assert(cpu->core_id <= 255);
> > > >
> > > > Where's the code that ensures this assert() line can't be
> > > > triggered by any command-line configuration?
> > >
> > > I did not understand this. Can you please elaborate. Thanks
> > 
> > The user must not be able to trigger an assert(), so we need to
> > ensure that core_id will never be larger than 255.  Is there
> > existing code that ensures that?
> 
> I see that max_cpus is set to 255 and also there are checks to make sure core_id does not go above 255.
> I verified it while testing.  So, probably we don't need assert here.  Radim asked me to add this assert.
> I can remove it if no abjections. 

Sorry for not replying to this before: no objection to the
assert(), especially considering it will trigger very early on
initialization if we break it one day.

-- 
Eduardo