From: olof@lixom•net (Olof Johansson)
To: Segher Boessenkool <segher@kernel•crashing.org>
Cc: linuxppc-dev@ozlabs•org, paulus@samba•org
Subject: Re: [PATCH] DMA 4GB boundary protection
Date: Sat, 3 Mar 2007 17:57:55 -0600 [thread overview]
Message-ID: <20070303235755.GC8028@lixom.net> (raw)
In-Reply-To: <8049bab22e1c006dcf916eb12202b73d@kernel.crashing.org>
On Sun, Mar 04, 2007 at 12:32:04AM +0100, Segher Boessenkool wrote:
> > The drawback of this patch is that it adds code to every single
> > allocation.
> > Instead, you should just mark the last entry before the 4GB boundary
> > as allocated when you setup the bitmaps for the table. That way, no
> > allocation will ever be able to cross over.
>
> Jake said that this bug happens when crossing _any_ 4GB
> boundary, so that means reserving a few more blocks.
Yes, sorry. I was presuming that the table provided by firmware was less
than 4GB in size. He would obviously need to mark at each boundary.
> > Even nicer would be to only do it when a boot option is specified, so
> > we actually have a chance to expose and find the driver bugs instead of
> > papering them over.
>
> Almost all drivers (*) that can do DAC already avoid
> crossing the SAC-to-DAC boundary. I have never heard
> about a card having the bug on _any_ 4GB crossing, I
> doubt they are that common. Just fix the drivers :-)
I can see the point with dealig with backports. Having a boot option
that is disabled by default would help working around it until a fix is
available, but it'd still help expose driver bugs.
-Olof
next prev parent reply other threads:[~2007-03-03 23:46 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-02 21:49 [PATCH] DMA 4GB boundary protection Jake Moilanen
2007-03-02 22:27 ` Olof Johansson
2007-03-03 8:27 ` Benjamin Herrenschmidt
2007-03-03 23:25 ` Olof Johansson
2007-03-04 5:17 ` Christoph Hellwig
2007-03-04 5:52 ` Olof Johansson
2007-03-03 23:29 ` Olof Johansson
2007-03-03 23:32 ` Segher Boessenkool
2007-03-03 23:57 ` Olof Johansson [this message]
2007-03-21 21:05 ` Jake Moilanen
2007-03-21 21:39 ` Olof Johansson
2007-03-22 17:53 ` Olof Johansson
2007-03-22 17:47 ` Jake Moilanen
2007-03-22 22:52 ` Segher Boessenkool
2007-03-27 20:10 ` Jake Moilanen
2007-03-27 20:55 ` Benjamin Herrenschmidt
2007-03-27 23:48 ` Paul Mackerras
2007-03-28 15:56 ` Olof Johansson
2007-03-28 18:17 ` Jake Moilanen
2007-03-28 23:23 ` Benjamin Herrenschmidt
2007-03-29 13:44 ` Jake Moilanen
2007-03-29 14:52 ` Olof Johansson
2007-03-29 21:54 ` Benjamin Herrenschmidt
2007-04-23 12:22 ` Paul Mackerras
2007-04-24 3:07 ` Olof Johansson
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