Re: [Xen-devel] [PATCH] X86: cpuid faulting feature enable

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 01/07/2011 16:48, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:

>> + if ( cpuid_faulting_flip )
>> + {
>> +  unsigned int enable;
>> +
>> +  enable = !is_hvm_vcpu(next) && (next->domain->domain_id != 0);
> 
> Excluding Dom0 here is perhaps questionable (as it could allow hiding
> features not supported by Xen from applications).

It's probably because of a need for raw cpuid in libxc/xc_cpuid_x86.c where
we need to detect things like long mode. We could do that another way, or
provide a new paravirtualised raw cpuid just for dom0.

Not a barrier to this patch going in imo.

I suppose HVM VCPUs are excluded because otherwise the new feature would be
unexpectedly enabled in non-root mode too, and make HVM guests crash? :-)

 -- Keir



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