Re: Add option to skip cpu feature and model verification in libvirt and rely on qemu 'enforce' option

On Wed, Nov 23, 2022 at 05:58:41PM +0530, manish.mishra wrote: > On 23/11/22 5:44 pm, Daniel P. Berrangé wrote: >> On Wed, Nov 23, 2022 at 12:51:39PM +0100, Jiri Denemark wrote: >>> On Wed, Nov 23, 2022 at 11:41:03 +0000, Daniel P. Berrangé wrote: >>>> Why can't it just use the exsting QEMU passthrough syntax we have. >>>> I don't think we should be adding specifial support just for CPUs >>> That would be nice, but the QEMU passthrough syntax cannot be used for >>> changing options that libvirt already passes to QEMU. So using it would >>> likely result in two separate -cpu options on QEMU command line. And it >>> would not rule out the CPU verification code in libvirt. Remember, we >>> add a default -cpu model in case there's none configured in the XML. >> Two -cpu options isn't a problem, the latter will override the former, >> which is fine from the level of support intended for QEMU passthrough >> usage. >> >> For the libvirt checking, isn't the 'check=none' attr sufficient >> to skip checks libvirt does. >> >> >> With regards, >> Daniel > Actually even within check='none' libvirt does few checks e.g. > virCPUValidateFeatures if feature string passed is proper and > defined in libvirt. We could extend check='none' to remove even > these kind of things. So Jiri suggested that making such kind > of changes in general path is not good idea so discussion went > to using separate cpu class <qemu:cpu>. There is no need to remove any such check, as you wouldn't be specifying any <cpu> element with custom features set, so the virCPUValidateFeuatres check should not be creating any problems at that point.

With regards, Daniel