From: "H. Peter Anvin" <hpa@zytor.com>
To: Linus Torvalds <torvalds@linux-foundation.org>,
Suresh Siddha <sbsiddha@gmail.com>
Cc: 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>
Subject: Re: [PATCH] Make math_state_restore() save and restore the interrupt flag
Date: Sat, 01 Feb 2014 11:35:50 -0800 [thread overview]
Message-ID: <52ED4C96.6020703@zytor.com> (raw)
In-Reply-To: <CA+55aFz-=9L=K2O-yB5f9R-w40PzXJ5xEXcinnUdUF1QHO7KMQ@mail.gmail.com>
On 02/01/2014 11:27 AM, Linus Torvalds wrote:
>
> (a) "we don't want to restore at all, because once the kernel starts
> using math, it might do so a lot, and saving/restoring is a bad idea":
>
> void __kernel_fpu_end(void)
> {
> stts();
> }
>
> *or*
>
> Quite frankly, I'd almost lean towards (a). Comments? Does anybody
> have any loads where the kernel does a lot of fpu stuff (ie network
> encryption using the hw engines or something)? I'd really like to hear
> if it makes a difference..
>
This will obviously not protect eageronly features (MPX, LWP, ...) so
this means those features are permanently unavailable to the kernel,
even inside kernel_fpu_begin/end. Now, currently I don't think we have
any plans to use those in the kernel (at least not in a way where
kernel_fpu_begin/end makes sense as bracketing), but it is something
worth keeping in mind.
-hpa
next prev parent reply other threads:[~2014-02-01 19:36 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-30 22:01 [PATCH] Make math_state_restore() save and restore the interrupt flag Nate Eldredge
2014-01-30 22:24 ` Linus Torvalds
2014-01-31 7:33 ` Suresh Siddha
2014-02-01 19:27 ` Linus Torvalds
2014-02-01 19:35 ` H. Peter Anvin [this message]
2014-02-01 19:46 ` Linus Torvalds
2014-02-01 20:00 ` H. Peter Anvin
2014-02-01 20:16 ` Linus Torvalds
2014-02-01 20:16 ` H. Peter Anvin
2014-02-01 21:17 ` George Spelvin
2014-02-01 21:36 ` H. Peter Anvin
2014-02-01 23:40 ` H. Peter Anvin
2014-02-02 0:17 ` Linus Torvalds
2014-02-02 1:19 ` George Spelvin
2014-02-02 1:25 ` H. Peter Anvin
2014-02-02 8:45 ` Pekka Riikonen
2014-02-02 1:06 ` Suresh Siddha
2014-02-02 1:26 ` H. Peter Anvin
2014-02-02 1:35 ` Suresh Siddha
2014-02-02 1:38 ` Linus Torvalds
2014-02-02 1:47 ` Suresh Siddha
2014-02-02 1:51 ` Linus Torvalds
2014-02-02 1:57 ` H. Peter Anvin
2014-02-02 2:05 ` Linus Torvalds
2014-02-02 2:12 ` H. Peter Anvin
2014-02-02 1:59 ` Suresh Siddha
2014-02-02 1:43 ` H. Peter Anvin
2014-02-02 1:47 ` Linus Torvalds
2014-02-02 7:19 ` Suresh Siddha
2014-02-02 19:15 ` Linus Torvalds
2014-02-03 6:56 ` Suresh Siddha
2014-02-03 18:20 ` Linus Torvalds
2014-02-04 6:03 ` Suresh Siddha
2014-02-06 5:26 ` Nate Eldredge
2014-02-06 5:34 ` George Spelvin
2014-02-13 15:45 ` Maarten Baert
2014-02-13 20:00 ` George Spelvin
2014-03-11 19:36 ` [tip:x86/urgent] x86, fpu: Check tsk_used_math() in kernel_fpu_end() for eager FPU tip-bot for Suresh Siddha
2014-02-27 23:44 ` [PATCH] Make math_state_restore() save and restore the interrupt flag H. Peter Anvin
2014-03-07 23:18 ` H. Peter Anvin
2014-03-08 6:18 ` Suresh Siddha
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=52ED4C96.6020703@zytor.com \
--to=hpa@zytor.com \
--cc=jack@suse.cz \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@horizon.com \
--cc=maarten-baert@hotmail.com \
--cc=mingo@kernel.org \
--cc=nate@thatsmathematics.com \
--cc=priikone@iki.fi \
--cc=sbsiddha@gmail.com \
--cc=stable@vger.kernel.org \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).