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Date: Sat, 1 Feb 2014 17:38:27 -0800
Message-ID: <CA+55aFw-im55F=6PJ1T-=dtmb4+NcnRpZ9nxx=+khUe+sLNxxw@mail.gmail.com>
Subject: Re: [PATCH] Make math_state_restore() save and restore the interrupt flag
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Suresh Siddha <sbsiddha@gmail.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
        Nate Eldredge <nate@thatsmathematics.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        stable <stable@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Maarten Baert <maarten-baert@hotmail.com>, Jan Kara <jack@suse.cz>,
        George Spelvin <linux@horizon.com>, Pekka Riikonen <priikone@iki.fi>
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Sender: linux-kernel-owner@vger.kernel.org

On Sat, Feb 1, 2014 at 5:35 PM, Suresh Siddha <sbsiddha@gmail.com> wrote:
> On Sat, Feb 1, 2014 at 5:26 PM, H. Peter Anvin <hpa@zytor.com> wrote:
>> Even "b" does that, no?
>
> oh right. It needs an else. only for non-eager fpu case we should do stts()

It definitely does not want an else, I think.

If tsk_used_math() is false, or if the FPU restore failed, we
*definitely* need that stts(). Otherwise we'd return to user mode with
random contents in the FP state, and let user mode muck around with
it.

No?

                     Linus
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