[libvirt-users] Question about disabling '3dnowprefetch' CPU feature in Xen Guest using libvirt

[Charles Shih]

Hi Jim,

  Thank you for the great support and expertise. It helps so much! :-)

Regards,
Charles

Charles Shih (史晨)
Quality Engineer
Red Hat, Platform QE, Virt QE, Section 1
Email: cheshi at redhat.com
IRC: cheshi @ #eng-china, #hyperv ,#qa, #virt
T: +86 10 65627484  - IP: 8387484
M: +86 18611268098


On Wed, Jul 5, 2017 at 11:42 PM, Jim Fehlig <jfehlig at suse.com> wrote:

> On 06/18/2017 09:01 PM, Charles Shih wrote:
>
>> Dear All,
>>
>>      I'm reaching this mail-list to ask a small question about disabling
>> '3dnowprefetch' CPU feature in Xen Guest using libvirt.
>>
>>      This is my environment:
>>      Fedora release 26 (Twenty Six)
>>      4.11.0-0.rc3.git0.2.fc26.x86_64
>>      xen-4.8.1-2.fc26.x86_64
>>      libvirt-3.2.1-1.fc26.x86_64
>>
>>      I can disable '3dnowprefetch' CPU feature in guest via 'xl' command,
>> with adding `cpuid='host,3dnowprefetch=0'` into the CFG file.
>>
>>      However, follow the instruction (https://libvirt.org/formatdom
>> ain.html#elementsCPU <https://libvirt.org/formatdomain.html#elementsCPU>),
>> I added the following block into my XML file:
>>
>> ```
>>    <cpu mode='host-passthrough' check='none'>
>>      <feature policy='disable' name='3dnowprefetch'/>
>>    </cpu>
>> ```
>>
>>      Created the instance, seemed this feature was not being disabled in
>> my guest. (I was able to see '3dnowprefetch' in `lscpu` outputs)
>>
>>      Anybody has idea on this? Does libvirt support this for Xen?
>>
>
> Currently, the libvirt libxl driver only supports VMX or SVM CPU feature,
> and for that you'd need libvirt 3.3.0
>
> http://libvirt.org/git/?p=libvirt.git;a=commit;h=c268b9eaeb4
> 321ef311ae2e152b80752918eb289
>
> More support for CPU customization is on the todo list. Contributions are
> always warmly welcomed :-).
>
> Regards,
> Jim
>
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