linux-kernel - Re: [RFC PATCH 06/11] x86,fpu: lazily skip fpu restore with eager fpu mode, too

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <54B58382.9030908@redhat.com>
Date:	Tue, 13 Jan 2015 15:43:46 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Andy Lutomirski <luto@...capital.net>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Matt Fleming <matt.fleming@...el.com>,
	Borislav Petkov <bp@...e.de>, Oleg Nesterov <oleg@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC PATCH 06/11] x86,fpu: lazily skip fpu restore with eager
 fpu mode, too

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 01/13/2015 12:11 PM, Andy Lutomirski wrote:
> On Sun, Jan 11, 2015 at 1:46 PM,  <riel@...hat.com> wrote:

>> diff --git a/arch/x86/include/asm/fpu-internal.h
>> b/arch/x86/include/asm/fpu-internal.h index 4db8781..a5a40c7
>> 100644 --- a/arch/x86/include/asm/fpu-internal.h +++
>> b/arch/x86/include/asm/fpu-internal.h @@ -435,13 +435,9 @@ static
>> inline void switch_fpu_prepare(struct task_struct *old, struct
>> task_struc old->thread.fpu.last_cpu = ~0; if (preload) { 
>> new->thread.fpu_counter++; -                       if
>> (!use_eager_fpu() && fpu_lazy_restore(new, cpu)) -
>> /* XXX: is this safe against ptrace??? */ -
>> __thread_fpu_begin(new); -                       else { +
>> set_thread_flag(TIF_LOAD_FPU); +                       if
>> (!fpu_lazy_restore(new, cpu)) prefetch(new->thread.fpu.state);
> 
> Is this prefetch still worth keeping?  Wouldn't prefetching the
> fpu effectively require grabbing more than one cacheline anyway?

Probably not. I'll drop it, for more code simplification.

- -- 
All rights reversed
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1

iQEcBAEBAgAGBQJUtYOCAAoJEM553pKExN6DDYMIAL3m7Nmlz8qiYrDEIhimHupj
JeIp92cdm+AcgeYydC9Tzz3cQrDExjJ3juI25OmjYF1rTHoRyFC/trWCjUajeKxa
rdxyHYmcNCvsmvEN9Ls3IfrRt4SF7iDKP9P9Qa49rakCprR82P2UUQ25zDuad8wR
n7G+nev1GNpsc8w8++ebczyEgVq579s2QA3x/mpO9FWA2DNrSndT1P7OxY6BBbEO
jcp/9V17rfZOvh7W9yCSRs9M5B3OzjACTktSTRWWuPHS7qBJa1/oeA7Z45Vgb9Bk
xxH1zS4IPcHu5WEB4FTDPYHoR7NOPWaXNDViU3NnV6jMzaCff1Vd6XgN5PHQhZc=
=y0qh
-----END PGP SIGNATURE-----
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/