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Date: Tue, 23 Jan 2007 10:42:02 -0500
From: Kyle McMartin <kyle@parisc-linux.org>
To: Yu-Chen Wu <g944370@oz.nthu.edu.tw>
Cc: "'Anton Altaparmakov'" <aia21@cam.ac.uk>, linux-kernel@vger.kernel.org
Subject: Re: Could convert a buffer that allocated by vmalloc to pages?
Message-ID: <20070123154202.GA8892@athena.road.mcmartin.ca>
References: <030701c73eef$0b4d0010$0100a8c0@sslabmayasky> <1169557944.4475.8.camel@imp.csi.cam.ac.uk> <030801c73ef8$f2198a00$0100a8c0@sslabmayasky>
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On Tue, Jan 23, 2007 at 10:15:33PM +0800, Yu-Chen Wu wrote:
> printk(KERN_INFO "vmalloc_to_page tpage :%x\n",tpage);
> //===========info of dmesg==================
<snip>
> [ 1561.768492] page allocated:60ea9000
> [ 1561.768497] vmalloc_to_page tpage :7fcf7e18
> 
> Why the page address get from vmalloc_to_page is different with the first
> page address of the vm_struct (73d65000)?
> 

Memory returned by vmalloc is only virtually contiguous, not physically
contiguous. If you're allocating memory for DMA, see the interface
documented in Documentation/DMA-mapping.txt for more information.

-- Kyle
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