On 05/09/2018 01:35 PM, Kashyap Chamarthy wrote:
On Tue, May 08, 2018 at 10:44:22AM -0400, Collin Walling wrote:
Hi
I have noticed something that may be misconstrued regarding the libvirt domain xml format for defining a cpu model. There seems to be a misalignment where the libvirt documentation states something that is not supported, but libvirt itself gives no clear indication of such. This is regarding the cpu mode "host-model" and providing a cpu model name between the <model> tags.
From the libvirt docs under header "CPU model and topology" paragraph "cpu" subparagraph "host-model", the following rule is defined (bolded or between asterisks):
"... The match attribute can't be used in this mode. *Specifying CPU model is not supported* either, but model's fallback attribute may still be used. ..."
https://libvirt.org/formatdomain.html#elementsCPU
The above rule reads as "if mode is 'host-model' (and the architecture is not PowerPC) then specifying a model name should not be allowed". However, this is not the observed behavior. For example, I can define and start a guest with the following xml snippet without any issues:
<cpu mode='host-model'> <model>cpu-name</model> </cpu>
After starting the guest, you still see the same as above when you do `virsh dumpxml $GUEST`? Also does the "cpu-name" of your choice really shows up when check the QEMU command-line for the guest?
After the domain is defined but not started: <cpu mode='host-model' check='partial'> <model fallback='allow'>cpu-name</model> </cpu> After the defined domain is started: <cpu mode='custom' match='exact' check='partial'> <model fallback='forbid'>z13.2-base</model> <feature policy='require' name='aen'/> <feature policy='require' name='aefsi'/> <feature policy='require' name='msa5'/> <feature policy='require' name='msa4'/> <feature policy='require' name='msa3'/> <feature policy='require' name='msa2'/> <feature policy='require' name='msa1'/> <feature policy='require' name='sthyi'/> <feature policy='require' name='edat'/> <feature policy='require' name='ri'/> <feature policy='require' name='edat2'/> <feature policy='require' name='vx'/> <feature policy='require' name='ipter'/> <feature policy='require' name='esop'/> <feature policy='require' name='cte'/> <feature policy='require' name='bpb'/> <feature policy='require' name='ppa15'/> <feature policy='require' name='zpci'/> <feature policy='require' name='sea_esop2'/> <feature policy='require' name='te'/> <feature policy='require' name='cmm'/> </cpu> and of course the cpu_name does not show up in the qemu command line. The question is if the model could not simply be ignored in the define scenario resulting in <cpu mode='host-model' check='partial'> <model fallback='allow'/> </cpu> which also gets generated when just defining the domain with <cpu mode='host-model'/> -- Mit freundlichen Grüßen/Kind regards Boris Fiuczynski IBM Deutschland Research & Development GmbH Vorsitzender des Aufsichtsrats: Martina Köderitz Geschäftsführung: Dirk Wittkopp Sitz der Gesellschaft: Böblingen Registergericht: Amtsgericht Stuttgart, HRB 243294