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From: Eduardo Habkost <ehabkost@redhat.com>
To: Vincent Bernat <vincent@bernat.im>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Richard Henderson <rth@twiddle.net>,
	qemu-devel@nongnu.org, Jiri Denemark <jdenemar@redhat.com>,
	Kashyap Chamarthy <kchamart@redhat.com>
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 10:41:11 -0200	[thread overview]
Message-ID: <20180116124111.GC627@localhost.localdomain> (raw)
In-Reply-To: <87zi5ite88.fsf@luffy.cx>

On Sat, Jan 13, 2018 at 08:22:31AM +0100, Vincent Bernat wrote:
>  ❦ 12 janvier 2018 16:47 -0200, Eduardo Habkost <ehabkost@redhat.com> :
> 
> > 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.

-- 
Eduardo

  reply	other threads:[~2018-01-16 12:41 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-09  7:01 [Qemu-devel] [PATCH x86-next v2] target-i386: add PCID flag to Westmere, Sandy Bridge and Ivy Bridge Vincent Bernat
2018-01-12 18:47 ` Eduardo Habkost
2018-01-13  7:22   ` Vincent Bernat
2018-01-16 12:41     ` Eduardo Habkost [this message]
2018-01-16 12:55       ` Vincent Bernat
2018-01-16 15:33         ` Kashyap Chamarthy
2018-01-16 17:08           ` Eduardo Habkost
2018-01-16 17:43             ` Daniel P. Berrange
2018-01-16 22:45               ` Kashyap Chamarthy

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