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From: Vincent Bernat <vincent@bernat.im>
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Date: Sat, 13 Jan 2018 08:22:31 +0100
In-Reply-To: <20180112184727.GJ6646@localhost.localdomain> (Eduardo Habkost's
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Subject: Re: [Qemu-devel] [PATCH x86-next v2] target-i386: add PCID flag to
 Westmere, Sandy Bridge and Ivy Bridge
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To: Eduardo Habkost <ehabkost@redhat.com>
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>

 =E2=9D=A6 12 janvier 2018 16:47 -0200, Eduardo Habkost <ehabkost@redhat.co=
m>=C2=A0:

> 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.
--=20
Avoid unnecessary branches.
            - The Elements of Programming Style (Kernighan & Plauger)