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From: Ingo Oeser <ioe-lkml@rameria.de>
To: Russell King <rmk@arm.linux.org.uk>
Cc: Andi Kleen <ak@muc.de>, Joe Korty <joe.korty@ccur.com>,
	linux-kernel@vger.kernel.org
Subject: Re: mlockall and mmap of IO devices don't mix
Date: Sat, 4 Oct 2003 12:02:08 +0200	[thread overview]
Message-ID: <200310041202.08742.ioe-lkml@rameria.de> (raw)
In-Reply-To: <20031004102221.A18928@flint.arm.linux.org.uk>

Hi there,

On Saturday 04 October 2003 11:22, you wrote:
> On Sat, Oct 04, 2003 at 11:17:03AM +0200, Andi Kleen wrote:
> > > This check is only done, if it is a valid pfn (pfn_valid()) of a
> > > present pte.
> >
> > pfn_valid is useless, it doesn't handle all IO holes on x86 for examples.
>
> Sounds like pfn_valid() is buggy on x86.  It's supposed to definitively
> indicate whether the PFN is a valid page of ram (and has a valid struct
> page entry.)  If it doesn't do that, the architecture implementation is
> wrong.

Looks like it. But it also has to be fast (see include/asm-i386/mmzone.h) 
and doesn't even hide the holes in NUMA machines. 

We had a page_is_ram() for this somewhere. I don't know, why this is
gone. It would be useful in other places as well.

If the page_is_ram() test could be done using the vma only now, this
would be even better and should be called vma_is_ram() to generalize
these corner cases (today and in the future) and make more
clear what these kind of tests want to do.

Regards

Ingo Oeser



  reply	other threads:[~2003-10-04 10:04 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CFYv.787.23@gated-at.bofh.it>
2003-10-04  7:02 ` Andi Kleen
2003-10-04  7:42   ` Andrew Morton
2003-10-04  8:29     ` Andi Kleen
2003-10-04  8:47   ` Ingo Oeser
2003-10-04  9:17     ` Andi Kleen
2003-10-04  9:22       ` Russell King
2003-10-04 10:02         ` Ingo Oeser [this message]
2003-10-04 10:13           ` Russell King
2003-10-04 14:19             ` Ingo Oeser
2003-10-04 14:32           ` Martin J. Bligh
2003-10-03 21:44 Joe Korty
2003-10-03 22:23 ` Andrew Morton
2003-10-03 22:55   ` Joe Korty
2003-10-03 23:06     ` Andrew Morton
2003-10-03 23:28       ` Joe Korty
2003-10-03 23:15     ` Andrew Morton
2003-10-03 23:54       ` Joe Korty
2003-10-04  0:27         ` Andrew Morton
2003-10-04  5:47           ` David S. Miller
2003-10-04  9:29             ` Ingo Oeser
2004-05-21 11:34 ` Mark Hounschell
2004-05-22  2:13   ` Andrew Morton
2004-05-22 10:47     ` Mark Hounschell
2004-05-23 12:58       ` Mark Hounschell
2004-05-25 14:27     ` Joe Korty
2004-05-25 19:47       ` Andrew Morton
2004-05-25 21:31         ` Joe Korty
2004-07-16 21:01         ` Mark Hounschell

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