From: Rene Herman <rene.herman@keyaccess.nl>
To: "David P. Reed" <dpreed@reed.com>
Cc: Robert Hancock <hancockr@shaw.ca>,
linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64 with MCP51 laptops
Date: Fri, 07 Dec 2007 08:34:04 +0100 [thread overview]
Message-ID: <4758F76C.1090207@keyaccess.nl> (raw)
In-Reply-To: <4758F373.6020901@keyaccess.nl>
On 07-12-07 08:17, Rene Herman wrote:
> On 07-12-07 06:54, David P. Reed wrote:
>
>> Pardon my ignorance, but is port 0xed really safe to push an out cycle
>> at across the entire x86_64 family?
>
> Please do not top-post. Who knows, probably not. You just experienced
> that 0x80 is apparently not safe for you and that one's the conventional
> choice so it's likely that someone somewhere will have problems with
> 0xed as well.
>
> That's why I adviced you'd test and see what blows up and suggested that
> in the absence of better fixes a 0x80/0xed port choice might be able to
> hang off machine types as retrievable from DMI or something.
>
> The better fix would probably be to simply udelay(1) but you need
> calibrated timers before you can do that and some googling leads me to
> believe that's why it's not today. There's also a possible issue in that
> an I/O access might serve as a method of flushing forwarding buffers on
> a PCI bridge but I have no idea if that's a real issue (and if it is, an
> inb() should suffice as well).
>
>> How long must real _p pauses be in reality?
>
> 8 ISA bus cycles is the intended delay it seems which at a typical ISA
> bus speed of 8 MHz amounts to 1 us.
>
>> (and who cares about what the code calls "really slow i/o").
>
> Paranoid programmers and those that need to delay for 4 us.
>
>> Why are we waiting at all? I read the comments in io_64.h, and am a
>> bit mystified. Does Windoze or DOS do this magical mystery wait?
>
> The CMOS example at hand is the standard example. It's accessed through
> an index/data register pair. You need to be sure that the RTC has
> switched the correct internal register to the data register before you
> poke at it or you may read/write the wrong one.
>
> Now, as said, I can't say I've ever in fact caught _any_ piece of
> hardware with its pants down like that and needing this for actual
> RTC/CMOS could as far as I'm aware be more of a left-over from The Olden
> Days with a bus more or less directly tied to the 8086 than sensible for
> anything on which Linux could run. Hard to test though and certainly for
> generic outb_p use.
>
> Yes, DOS or at least many programs that ran under it did very similar
> things but DOS ofcourse originated on those first PCs.
>
>> Anyway, the virtualization hooks in 32-bit x86 almost make it possible
>> to isolate this simply - maybe - after the merge of 32/64 being
>> contemplated.
>>
>> And anyone who knows what the chipset might be doing with the 80 port
>> rather than POST codes, perhaps could contribute. Any nvidia folks
>> who know what's happening under NDA? Any Phoenix BIOS types?
>
> It's fairly surprising that 0x80 is given you trouble. It's a very well
> known legacy port. Even though it may not be all that sensible a thing
> today I'd say that if your machine put anything other than an actual
> integrated POST monitor on port 0x80 it in fact fucked up.
This is a good thread to read:
http://linux.derkeiler.com/Mailing-Lists/Kernel/2003-09/5700.html
maybe you have some LPC device that gets confused by aborts on the bus as well.
Rene.
next prev parent reply other threads:[~2007-12-07 7:35 UTC|newest]
Thread overview: 109+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <fa./27SNSh+L5T3iqFNPdHClEu+yT0@ifi.uio.no>
2007-12-07 0:23 ` RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64 with MCP51 laptops Robert Hancock
2007-12-07 5:09 ` Rene Herman
2007-12-07 5:54 ` David P. Reed
2007-12-07 7:17 ` Rene Herman
2007-12-07 7:34 ` Rene Herman [this message]
2007-12-07 10:49 ` Andi Kleen
2007-12-06 22:38 David P. Reed
2007-12-07 0:15 ` Alan Cox
2007-12-07 10:44 ` Andi Kleen
2007-12-07 14:50 ` David P. Reed
2007-12-05 11:10 ` Pavel Machek
2007-12-08 0:21 ` Andi Kleen
2007-12-07 14:54 ` Andi Kleen
2007-12-07 15:43 ` Rene Herman
2007-12-07 16:28 ` Rene Herman
2007-12-11 0:31 ` H. Peter Anvin
2007-12-11 5:53 ` H. Peter Anvin
2007-12-07 16:04 ` Alan Cox
2007-12-07 16:31 ` Andi Kleen
2007-12-07 17:19 ` Alan Cox
2007-12-07 18:45 ` Rene Herman
2007-12-07 18:42 ` Alan Cox
2007-12-07 19:25 ` Rene Herman
2007-12-07 21:45 ` Alan Cox
2007-12-08 19:25 ` David P. Reed
2007-12-08 19:50 ` Andi Kleen
2007-12-08 20:47 ` David P. Reed
2007-12-08 21:04 ` Alan Cox
2007-12-08 20:26 ` Alan Cox
2007-12-11 5:58 ` H. Peter Anvin
2007-12-09 5:04 ` Rene Herman
2007-12-09 13:22 ` Pavel Machek
2007-12-11 15:14 ` Lennart Sorensen
2007-12-09 12:54 ` Pavel Machek
2007-12-09 13:41 ` Dr. David Alan Gilbert
2007-12-09 15:54 ` Ondrej Zary
2007-12-09 16:59 ` Andi Kleen
2007-12-09 21:25 ` Pavel Machek
2007-12-09 22:29 ` Alan Cox
2007-12-09 23:22 ` Pavel Machek
2007-12-10 12:02 ` Alan Cox
2007-12-10 4:17 ` Rene Herman
2007-12-10 11:30 ` Krzysztof Halasa
2007-12-10 12:08 ` Rene Herman
2007-12-10 18:02 ` Ondrej Zary
2007-12-11 1:10 ` David Newall
2007-12-11 1:25 ` H. Peter Anvin
2007-12-11 1:42 ` David Newall
2007-12-11 1:46 ` H. Peter Anvin
2007-12-11 1:51 ` H. Peter Anvin
2007-12-11 7:40 ` Paul Rolland
2007-12-11 9:50 ` Rene Herman
2007-12-11 12:08 ` David Newall
2007-12-11 13:16 ` Rene Herman
2007-12-11 13:32 ` Paul Rolland
2007-12-11 14:15 ` Rene Herman
2007-12-11 15:28 ` Rene Herman
2007-12-11 15:37 ` Paul Rolland
2007-12-11 15:53 ` Rene Herman
2007-12-11 16:58 ` David P. Reed
2007-12-11 17:01 ` Rene Herman
2007-12-11 17:05 ` H. Peter Anvin
2007-12-11 17:32 ` Alan Cox
2007-12-11 19:19 ` David P. Reed
2007-12-11 19:36 ` Pavel Machek
2007-12-11 20:16 ` Alan Cox
2007-12-11 20:27 ` linux-os (Dick Johnson)
2007-12-11 20:34 ` Rene Herman
2007-12-11 21:03 ` David P. Reed
2007-12-11 23:56 ` David P. Reed
2007-12-12 13:11 ` linux-os (Dick Johnson)
2007-12-12 16:12 ` Alan Cox
2007-12-14 14:33 ` Ingo Molnar
2007-12-16 21:26 ` Pavel Machek
2007-12-17 0:02 ` Alan Cox
2007-12-17 0:03 ` Alan Cox
2007-12-17 0:28 ` Pavel Machek
2007-12-17 14:42 ` Ingo Molnar
2007-12-27 10:39 ` Pavel Machek
2007-12-11 16:32 ` John Stoffel
2007-12-11 16:40 ` Rene Herman
2007-12-11 13:50 ` David Newall
2007-12-11 14:14 ` Rene Herman
2007-12-11 14:25 ` Alan Cox
2007-12-12 22:18 ` David Newall
2007-12-12 23:00 ` Alan Cox
2007-12-13 13:13 ` David P. Reed
2007-12-13 13:21 ` Alan Cox
2007-12-14 1:50 ` David P. Reed
2007-12-14 15:16 ` Alan Cox
2007-12-11 15:41 ` linux-os (Dick Johnson)
2007-12-11 16:30 ` Andi Kleen
2007-12-11 16:50 ` Rene Herman
2007-12-11 17:00 ` David P. Reed
2007-12-11 17:04 ` Rene Herman
2007-12-11 17:27 ` Rene Herman
2007-12-11 19:18 ` Pavel Machek
2007-12-11 19:16 ` Pavel Machek
2007-12-11 19:59 ` Rene Herman
2007-12-11 19:59 ` Rene Herman
2007-12-11 20:00 ` Rene Herman
2007-12-11 20:00 ` Rene Herman
2007-12-11 13:14 ` Alan Cox
2007-12-11 13:32 ` Andi Kleen
2007-12-11 13:47 ` Pavel Machek
2007-12-11 13:50 ` Andi Kleen
2007-12-14 13:33 ` Ingo Molnar
2007-12-11 6:54 ` Rene Herman
2007-12-11 17:01 ` H. Peter Anvin
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