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Re: [Qemu-devel] [PATCH x86-next v2] target-i386: add PCID flag to Westm
From: |
Vincent Bernat |
Subject: |
Re: [Qemu-devel] [PATCH x86-next v2] target-i386: add PCID flag to Westmere, Sandy Bridge and Ivy Bridge |
Date: |
Tue, 16 Jan 2018 13:55:22 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.2 (gnu/linux) |
❦ 16 janvier 2018 10:41 -0200, Eduardo Habkost <address@hidden> :
>> > Adding Westmere-PCID would require adding a Westmere-PCID-IBRS
>> > CPU model too, so this is starting to look a bit ridiculous.
>> > Sane VM management systems would know how to use
>> > "-cpu Westmere,+pcid" without requiring new CPU model entries in
>> > QEMU. What's missing in existing management stacks to allow that
>> > to happen?
>>
>> That's what I actually do. So, I am fine with the solution of doing
>> nothing. However, it would be nice for unaware people to get the speedup
>> of pcid without knowing about it. Maybe we can just forget about
>> Westmere and still apply it to Sandy Bridge and Ivy Bridge.
>
> If management stacks today don't let the user choose
> "Westmere,+pcid", we probably have no other choice than adding a
> Westmere-PCID CPU model. But our management stacks need to be
> fixed so we won't need similar hacks in the future.
With libvirt:
<cpu mode='custom' match='exact'>
<model>Westmere</model>
<feature policy='require' name='pcid'/>
</cpu>
We are using CloudStack on top of that and it's also an available
option. However, looking at OpenStack, it doesn't seem possible:
https://github.com/openstack/nova/blob/6b248518da794a4c82665c22abf7bee5aa527a47/nova/conf/libvirt.py#L506
--
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and wants it back the minute it begins to rain.
-- Mark Twain
- [Qemu-devel] [PATCH x86-next v2] target-i386: add PCID flag to Westmere, Sandy Bridge and Ivy Bridge, Vincent Bernat, 2018/01/09
- Re: [Qemu-devel] [PATCH x86-next v2] target-i386: add PCID flag to Westmere, Sandy Bridge and Ivy Bridge, Eduardo Habkost, 2018/01/12
- Re: [Qemu-devel] [PATCH x86-next v2] target-i386: add PCID flag to Westmere, Sandy Bridge and Ivy Bridge, Vincent Bernat, 2018/01/13
- Re: [Qemu-devel] [PATCH x86-next v2] target-i386: add PCID flag to Westmere, Sandy Bridge and Ivy Bridge, Eduardo Habkost, 2018/01/16
- Re: [Qemu-devel] [PATCH x86-next v2] target-i386: add PCID flag to Westmere, Sandy Bridge and Ivy Bridge,
Vincent Bernat <=
- Re: [Qemu-devel] [PATCH x86-next v2] target-i386: add PCID flag to Westmere, Sandy Bridge and Ivy Bridge, Kashyap Chamarthy, 2018/01/16
- Re: [Qemu-devel] [PATCH x86-next v2] target-i386: add PCID flag to Westmere, Sandy Bridge and Ivy Bridge, Eduardo Habkost, 2018/01/16
- Re: [Qemu-devel] [PATCH x86-next v2] target-i386: add PCID flag to Westmere, Sandy Bridge and Ivy Bridge, Daniel P. Berrange, 2018/01/16
- Re: [Qemu-devel] [PATCH x86-next v2] target-i386: add PCID flag to Westmere, Sandy Bridge and Ivy Bridge, Kashyap Chamarthy, 2018/01/16