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

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/ 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? Any help would be appreciated. Thank you in advance. Regards, Charles Charles Shih (史晨) Quality Engineer Red Hat, Platform QE, Virt QE, Section 1 Email: cheshi(a)redhat.com IRC: cheshi @ #eng-china, #hyperv ,#qa, #virt T: +86 10 65627484 <010%206562%207484> - IP: 8387484 M: +86 18611268098 <186%201126%208098>