[Starlingx-discuss] Support IBRS cpu model.

Sun, Austin austin.sun at intel.com
Sat Nov 17 02:59:21 UTC 2018


Hi Chris:
      Thanks your review.  I have made new patch [1] based on your suggestion.  Could you help review it again ? 

https://github.com/austinsun/stx-nova/commit/3255facb16b70b138ff12243822b43d1824f6890#diff-6955c78b8a0da8ec1cbf33c3834de1e0

Thanks.
BR
Austin Sun. 

-----Original Message-----
From: Chris Friesen [mailto:chris.friesen at windriver.com] 
Sent: Friday, November 16, 2018 11:50 PM
To: starlingx-discuss at lists.starlingx.io
Subject: Re: [Starlingx-discuss] Support IBRS cpu model.

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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> Starlingx-discuss at lists.starlingx.io
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