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Subject: Re: Linux patch disabling AVX when eagerfpu is turned off - possibly
 not required
To: Dave Hansen <dave.hansen@intel.com>,
        Leonid Shatz <leonid.shatz@ravellosystems.com>,
        "'Ingo Molnar'" <mingo@kernel.org>, linux-kernel@vger.kernel.org,
        "'Yu-cheng Yu'" <yu-cheng.yu@intel.com>,
        "'Andy Lutomirski'" <luto@amacapital.net>,
        "'Borislav Petkov'" <bp@alien8.de>,
        "'Fenghua Yu'" <fenghua.yu@intel.com>,
        "'Linus Torvalds'" <torvalds@linux-foundation.org>,
        "'Oleg Nesterov'" <oleg@redhat.com>,
        "'Peter Zijlstra'" <peterz@infradead.org>,
        "'Quentin Casasnovas'" <quentin.casasnovas@oracle.com>,
        "'Ravi V. Shankar'" <ravi.v.shankar@intel.com>,
        "'Sai Praneeth Prakhya'" <sai.praneeth.prakhya@intel.com>,
        "'Thomas Gleixner'" <tglx@linutronix.de>
References: <02fd01d15437$233056c0$69910440$@ravellosystems.com>
 <56A13AC7.2040601@intel.com>
Cc: liran.alon@ravellosystems.com, mendel.aizner@ravellosystems.com,
        "'Elazar Leibovich'" <elazar.leibovich@ravellosystems.com>,
        "'Eyal Moscovici'" <eyal.moscovici@ravellosystems.com>,
        gil.hoffer@ravellosystems.com
From: "H. Peter Anvin" <hpa@zytor.com>
Message-ID: <56A13B88.1090505@zytor.com>
Date: Thu, 21 Jan 2016 12:11:52 -0800
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On 01/21/16 12:08, Dave Hansen wrote:
> On 01/21/2016 02:33 AM, Leonid Shatz wrote:
>> In view of above findings we would like to suggest to double check if
>> disabling AVX together with "eagerfpu off" is actually required and is a
>> real necessity. It would be helpful to consult with Intel engineers
>> regarding related design details.
> 
> Hi Leonid,
> 
> Thanks for the report!
> 
> Are you aware of any actual eagerfpu=off use in practice, or is this
> mostly a theoretical concern?
> 

Looking into this, FWIW.

	-hpa