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Re: [Qemu-devel] [PATCH 2/2] target-i386: Haswell-noTSX and Broadwell-no

From: Eduardo Habkost
Subject: Re: [Qemu-devel] [PATCH 2/2] target-i386: Haswell-noTSX and Broadwell-noTSX
Date: Thu, 19 Mar 2015 15:02:27 -0300
User-agent: Mutt/1.5.23 (2014-03-12)

On Mon, Mar 16, 2015 at 10:24:51AM +0000, Daniel P. Berrange wrote:
> On Fri, Mar 13, 2015 at 04:09:57PM -0300, Eduardo Habkost wrote:
> > With the Intel microcode update that removed HLE and RTM, there will be
> > different kinds of Haswell and Broadwell CPUs out there: some that still
> > have the HLE and RTM features, and some that don't have the HLE and RTM
> > features. On both cases people may be willing to use the pc-*-2.3
> > machine-types.
> > 
> > So, to cover both cases, introduce Haswell-noTSX and Broadwell-noTSX CPU
> > models, for hosts that have Haswell and Broadwell CPUs without TSX support.
> > 
> > Signed-off-by: Eduardo Habkost <address@hidden>
> The addition of Haswell-noTSX looks good to me.
> I'm unclear on whether we truely need Broadwell-noTSX though. Did
> Intel actually ship any Broadwell production silicon in which the
> microcode disables this feature, or was it only a problem on
> pre-production samples of Broadwell ? If the latter, I'd say we
> don't need to have a Broadwell-noTSX model added. Perhaps Jun/Don
> can confirm from Intel's side.

I've talked to Don and Jun, and they confirmed that a Broadwell-noTSX
CPU model will be needed, too.

I see some Broadwell CPUs without TSX-NI on ark.intel.com, too, so the
TSX errata wouldn't be the only reason for needing the -noTSX model.


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