[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <452D626E.9040606@tungstengraphics.com>
Date: Wed, 11 Oct 2006 23:30:22 +0200
From: Thomas Hellström <thomas@...gstengraphics.com>
To: Nick Piggin <npiggin@...e.de>
CC: Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [patch 4/5] mm: add vm_insert_pfn helpler
Nick Piggin wrote:
>On Wed, Oct 11, 2006 at 12:12:19PM +0200, Thomas Hellstrom wrote:
>
>
>>Nick, I just realized: would it be possible to have a pgprot_t argument
>>to this one, instead of it using vma->vm_pgprot?
>>
>>The motivation for this (DRM again) is that some architectures (powerpc)
>>cannot map the AGP aperture through IO space, but needs to remap the
>>page from memory with a nocache attribute set. Others need special
>>pgprot settings for write-combined mappings.
>>
>>Now, there's a possibility to change vma->vm_pgprot during the first
>>->fault(), but again, we only have the mmap_sem in read mode.
>>
>>
>
>I don't see a problem with that. It would be nice if vm_pgprot could
>be kept in synch with the pte protections, but I guess a crazy
>driver should be allowed to do anything it wants ;)
>
>
>
>
:).
Actually, the caching bits are sort of left out from the mm code anyway.
For example, mprotect will reset them, which is sort of a security risc,
since an unpriviliged user can call mprotect on uncached page mappings,
causing inconsistent mappings and stability problems.
Thomas
-
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/
Powered by blists - more mailing lists