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]
Date:	Sat, 01 Feb 2014 13:36:54 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	George Spelvin <linux@...izon.com>, torvalds@...ux-foundation.org
CC:	jack@...e.cz, linux-kernel@...r.kernel.org,
	maarten-baert@...mail.com, mingo@...nel.org,
	nate@...tsmathematics.com, priikone@....fi, sbsiddha@...il.com,
	stable@...r.kernel.org, tglx@...utronix.de, x86@...nel.org
Subject: Re: [PATCH] Make math_state_restore() save and restore the interrupt flag

It would be good to know how often #3 happens on a real workload.

On February 1, 2014 1:17:10 PM PST, George Spelvin <linux@...izon.com> wrote:
>> .. which *does* actually bring up something that might work, and
>might
>> be a good idea: remove the "restore math state or set TS" from the
>> normal kernel paths *entirely*, and move it to the "return to user
>> space" phase.
>
>This definitely seems much more sensible.  For processors without
>optimized context save/restore, the decision whether to restore eagerly
>is best made once the kernel has decided what it's returning *to*.
>
>>From an interrupt handler, there are now three cases:
>1) FPU not in use, available for immediate use.
>2) FPU in use by user-space; save to <location> before using.
>3) FPU in use by kernel code; may not be used (unless we want
>   to add nested FPU state save hair).

-- 
Sent from my mobile phone.  Please pardon brevity and lack of formatting.
--
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/

Powered by blists - more mailing lists