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Re: [Qemu-devel] [PATCH] target-i386: add pcid to both Sandy Bridge and
From: |
Eduardo Habkost |
Subject: |
Re: [Qemu-devel] [PATCH] target-i386: add pcid to both Sandy Bridge and Ivy Bridge |
Date: |
Mon, 8 Jan 2018 20:28:53 -0200 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
On Mon, Jan 08, 2018 at 11:22:36PM +0100, Vincent Bernat wrote:
> ❦ 8 janvier 2018 20:14 -0200, Eduardo Habkost <address@hidden> :
>
> >> What are the consequences of running a too old kernel? Would KVM just
> >> hide PCID flag?
> >
> > On an old kernel, the SandyBridge and IvyBridge CPU models will
> > be unexpectedly become not runnable.
>
> But, isn't it the same for more recent models that already have PCID
> enabled?
Yes, the more recent models are already not runnable on those
hosts. The key here is "unexpectedly": management software can
assume that the CPU model won't become unrunnable when it was
runnable in the past, and logic that decides if/where a VM can be
started (or migrated to) might break.
--
Eduardo