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Re: [Xen-devel] Insane contiguous physical memory requirements in blkbk/

To: "Stephen C. Tweedie" <sct@xxxxxxxxxx>
Subject: Re: [Xen-devel] Insane contiguous physical memory requirements in blkbk/blktap
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Thu, 05 Oct 2006 17:19:05 +0100
Cc: Aron Griffis <aron@xxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
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On 5/10/06 17:10, "Stephen C. Tweedie" <sct@xxxxxxxxxx> wrote:

>> This is easily fixable. Anywhere we use the virtual address to compute an
>> offset into a state structure, we can instead store the appropriate 'slot
>> index' in a spare field in the appropriate 'struct page'.
> 
> As far as I can tell, nothing uses the VA in any way --- it can't,
> because the start of the order-10 kmalloc area is not actually used
> anywhere after the initial mmap setup.  After making the variable
> mmap_vstart local to the __init function, everything still compiles, so
> I don't think there's anything lurking in header files that implicitly
> relies on it.

I'm thinking of netback. That's the one driver where I think we use a
virtual address (actually page-struct pointer) as a handle to
driver-internal state.

 -- Keir



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