linux-kernel - Re: [PATCH] Make math_state_restore() save and restore the interrupt flag

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

On Sat, Feb 1, 2014 at 5:35 PM, Suresh Siddha <sbsiddha@...il.com> wrote:
> On Sat, Feb 1, 2014 at 5:26 PM, H. Peter Anvin <hpa@...or.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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