[Starlingx-discuss] Support IBRS cpu model.

[Chris Friesen]

There's a problem with this patch.  The way the VCpuModelFilter is 
designed, the basic idea is that a host with a CPU model "later" in the 
list can support guests with all CPU models "earlier" in the list.

According to [1] the "spec-ctrl" and "ssbd" CPU features require host 
CPU microcode (i.e. that the host is detected as the "-IBRS" model) 
before it can be used for guest CPUs.  This means that a 
"Skylake-Server" host cannot support a "Broadwell-IBRS" guest, which 
violates the design of the VCpuModelFilter.

I think as part of adding the -IBRS models we'll have to also modify the 
filter itself.

Chris


[1] 
https://www.berrange.com/posts/2018/06/29/cpu-model-configuration-for-qemu-kvm-on-x86-hosts/


On 11/13/2018 11:54 PM, Sun, Austin wrote:
> Hi All:
>       if install StarlingX in compute-node with cpu type  'Skylake-Server-IBRS' ,  it cannot use  'passthrough' type with keyword hw:cpu_model in favor to create instance
>       It will prompt "No valid host was found. There are not enough hosts available. computer-0: (VCpuModelFilter) Host VCPU model Skylake-Server-IBRS required Passthrough Code 501"
>       After investigation ,  Libvirt 4.7.0 supports *IBRS (for example IvyBridge-IBRS, Skylake-Server-IBRS)  CPU model , but nova and meta favor does not support *IBRS CPU model yet.
>       
>       I have made patch for nova[0] and glance[1].
>        Nova[0] will support *-IBRS type vcpu when select passthrough
>        Glance[1] will add metadata to support *-IBRS in hw:cpu_model
>        
>     Please review these PRs.
> 
> Thanks.
> BR
> Austin Sun.
> 
>     [0] https://github.com/starlingx-staging/stx-nova/pull/15
>     [1] https://github.com/starlingx-staging/stx-glance/pull/4
> 
> 
> 
> 
> 
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