linux-kernel - Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override

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: <47780888.9070503@keyaccess.nl>
Date:	Sun, 30 Dec 2007 22:07:20 +0100
From:	Rene Herman <rene.herman@...access.nl>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	dpreed@...d.com, Islam Amer <pharon@...il.com>, hpa@...or.com,
	Pavel Machek <pavel@....cz>, Ingo Molnar <mingo@...hat.com>,
	Andi Kleen <andi@...stfloor.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override

On 30-12-07 21:46, Ingo Molnar wrote:
> * Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
> 
>>> So the current plan is to go with an io_delay=udelay default in v2.6.25, 
>>> to give this a migration window, and io_delay=none in v2.6.26 [and a 
>>> complete removal of arch/x86/kernel/io_delay.c], once the _p() uses are 
>>> fixed up. This is gradual enough to notice any regressions we care about 
>>> and also makes it nicely bisectable and gradual.
>> You will break systems if you blindly go around disabling _p delays 
>> for ISA and LPC bus devices. The DEC Hinote laptops for example are 
>> well known for requiring the correct ISA and other keyboard controller 
>> delays. I don't expect anyone to test with a hinote or see it until it 
>> hits Debian or similar 'low resource' friendly devices.
> 
> well, using io_delay=udelay is not 'blindly disabling'.

On the other hand, the patch you just posted that makes io_delay=none the 
default _is_ blindly disabling. So that wasn't for consumption?

io_delay=udelay additionally blindly disables the race-hiding effect the 
outb has on SMP and that Alan is seeing so many of. Should also wait for 
more driver review.

Rene.
--
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/