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Date: Thu, 29 Jan 2015 13:43:15 -0800
From: Dave Hansen <dave.hansen@linux.intel.com>
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To: Oleg Nesterov <oleg@redhat.com>
CC: Rik van Riel <riel@redhat.com>, Suresh Siddha <sbsiddha@gmail.com>,
        Andy Lutomirski <luto@amacapital.net>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Fenghua Yu <fenghua.yu@intel.com>,
        the arch/x86 maintainers <x86@kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/3]: x86, fpu: unlazy_fpu fixes/cleanups
References: <54C2A245.4010307@redhat.com> <20150129210723.GA31584@redhat.com> <54CAA357.1070108@linux.intel.com> <20150129213346.GA32511@redhat.com>
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On 01/29/2015 01:33 PM, Oleg Nesterov wrote:
> On 01/29, Dave Hansen wrote:
>>
>> On 01/29/2015 01:07 PM, Oleg Nesterov wrote:
>>> On 01/23, Rik van Riel wrote:
>>>>> Not only is this broken with my new code, but it looks like it may
>>>>> be broken with the current code, too...
>>> Lets (try to) fix unlazy_fpu/save_init_fpu at least.
>>>
>>> Dave, fpu_save_init() in do_bounds() and task_get_bounds_dir() looks
>>> wrong too, shouldn't it use unlazy_fpu() ? See the changelog in 3/3.
>>
>> IIRC, the 'cpu_has_xsaveopt' on the CPUs that support will MPX will
>> enable eagerfpu.
> 
> unless eagerfpu=off? but this doesn't matter.

Yeah, that's true.  That would also explain why I haven't run in to this
at all in testing.

Ugh, fpu_save_init() says it isn't preempt safe anyway, so we shouldn't
be using it.

I'll send a fix.