linux-kernel - Re: [PATCH 4/6] x86,fpu: use disable_task_lazy_fpu

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: <54D4EEF5.2020901@redhat.com>
Date:	Fri, 06 Feb 2015 11:42:29 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
CC:	dave.hansen@...ux.intel.com, sbsiddha@...il.com,
	luto@...capital.net, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, fenghua.yu@...el.com, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/6] x86,fpu: use disable_task_lazy_fpu_restore helper

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

On 02/02/2015 02:21 PM, Oleg Nesterov wrote:
> I'll try to read this patch tomorrow. Too late for me.
> 
> I think it is fine, but
> 
> On 02/02, riel@...hat.com wrote:
>> 
>> This also fixes the lazy FPU restore disabling in drop_fpu,
>> which only really works when !use_eager_fpu(). ...
>> 
>> --- a/arch/x86/include/asm/fpu-internal.h +++
>> b/arch/x86/include/asm/fpu-internal.h @@ -396,7 +396,7 @@ static
>> inline void drop_fpu(struct task_struct *tsk) * Forget
>> coprocessor state.. */ preempt_disable(); -
>> tsk->thread.fpu_counter = 0; +
>> task_disable_lazy_fpu_restore(tsk); __drop_fpu(tsk); 
>> clear_used_math();
> 
> perhaps this makes sense anyway, but I am not sure if the changelog
> is right.
> 
> Note that we clear PF_USED_MATH, last_fpu/has_fpu have no effect
> after this.

After a few days on the RCU code, I'm back to this :)

You are right, I should drop the change above from the patch,
and disable lazy fpu restore explicitly in places where we
need it.

I will send a v2 of these patches, without patch 6/6.

Ingo, would you like me to also re-send Oleg's FPU patches that are
not in -tip yet?

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

iQEcBAEBAgAGBQJU1O71AAoJEM553pKExN6DUtEH/R8X02MHD7GUxO4hyiLECL9f
SQDdF1l+1rqcQo7e+5nRJ5/rFvAIaNA5oBMOZJ9MlJRd6HOKS+VqLLpb8idvApeK
zRiYUdeyoui3e0po2nNCx/GBfXqMYca+qH4JMMq6gzv0c9Nm9Zq9pbKDbO2znns8
10YQexvZsHUiJgt63YoZSwxFKD1iAhnTOGBhZOJu/s27Qtu+7gyuyIcuMMDFj2eu
ACGqZPcjG2u7TlC+D4uivSferMrduNnWsxGq3AY32/nNhjKGmXaFJxRHDdCsYAGJ
+S+SFuUWq6JoD7MuC02NQyAs/bQzqhVfn8v7gm2gromqIIQGzBABtI+Em0LGFP4=
=3R+T
-----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/