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: <20071230160751.GB26221@elte.hu>
Date:	Sun, 30 Dec 2007 17:07:51 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Rene Herman <rene.herman@...access.nl>
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


* Rene Herman <rene.herman@...access.nl> wrote:

> On 30-12-07 16:28, Ingo Molnar wrote:
>
>> Reading from the 0x3cc port does not impact the cursor position update 
>> sequence IIRC - i think the vidport is even ignored for the input 
>> direction by most hardware, there's a separate input register. The 0x3cc 
>> port is a well-defined VGA register which should be unused on non-VGA 
>> hardware. (which makes it a perfect delay register in any case)
>
> Hardly. Duron 1300 on AMD756:

but that does not matter at all: that's not '90s era hardware that we 
are (slightly) worried about wrt. IO delays in misc_32.c. (i.e. on 
_real_ ISA systems)

> rene@...e4:~/src/port80$ su -c ./port80
> cycles: out 2400, in 2401
> rene@...e4:~/src/port80$ su -c ./port3cc
> cycles: out 459, in 394

of course, since VGA is implemented in the southbridge or on the video 
card, so it's much faster than a true ISA cycle.

the only (minor) worry we have here is really ancient systems relying on 
delays there. Modern VGA hardware most definitely does not need any such 
delays.

	Ingo
--
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/