Re: [Qemu-devel] [RFC PATCH v1 17/22] target-i386: add cpuid Fn8000_001f

[Eduardo Habkost]

On Wed, Sep 21, 2016 at 11:20:59AM -0500, Brijesh Singh wrote:
> On 09/13/2016 06:07 PM, Paolo Bonzini wrote:
> > On 13/09/2016 16:49, Brijesh Singh wrote:
[...]
> > > +    case 0x8000001F:
> > > +        host_cpuid(index, 0, eax, ebx, ecx, edx);
> > > +        break;

Do we really need to expose the raw host CPUID values directly to
the guest? It will make it harder to support migration later.


> > >      case 0xC0000000:
> > >          *eax = env->cpuid_xlevel2;
> > >          *ebx = 0;
> > > 
> > > 
> > > 
> > 
> > This should only be visible to a SEV-enabled guest.  Also, the xlevel
> > should be bumped to 0x8000001F for SEV-enabled guests.
> > 
> 
> Okay I will add sev_enabled() check before getting the cpuid.
> 
> Regarding xlevel, I am not able to locate qemu code which bumped the xelevel
> for KVM enabled guests.

Because QEMU doesn't do that automatically (yet), except for
CPUID[7].EBX features.

> Maybe I am missing something, looking at code gave
> me impression that xlevel is obtained using CPUID_80000000. One of the KVM
> RFC patch [1] updates the min level. Do I need to do something more into
> qemu to bumped the xlevel?

I will send a series today that will increase level/xlevel
automatically depending on the features that are enabled. I will
add you to CC.

-- 
Eduardo