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Re: [Xen-devel] [PATCH] X86: cpuid faulting feature enable
| To: | Jan Beulich <JBeulich@xxxxxxxxxx>, Jinsong Liu <jinsong.liu@xxxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] [PATCH] X86: cpuid faulting feature enable |
| From: | Keir Fraser <keir.xen@xxxxxxxxx> |
| Date: | Fri, 01 Jul 2011 17:07:52 +0100 |
| Cc: | Kevin Tian <kevin.tian@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Haitao Shan <haitao.shan@xxxxxxxxx>, Xin Li <xin.li@xxxxxxxxx> |
| Delivery-date: | Fri, 01 Jul 2011 09:09:04 -0700 |
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| Thread-topic: | [Xen-devel] [PATCH] X86: cpuid faulting feature enable |
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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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