linux-kernel - Re: [Xen-devel] Re: [patch 12/21] Xen-paravirt: Allocate and free vmalloc areas

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Date:	Fri, 16 Feb 2007 23:29:57 +0000
From:	Keir Fraser <Keir.Fraser@...cam.ac.uk>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	Keir Fraser <keir@...source.com>,
	Ian Pratt <ian.pratt@...source.com>,
	<xen-devel@...ts.xensource.com>,
	Chris Wright <chrisw@...s-sol.org>,
	<virtualization@...ts.osdl.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	<linux-kernel@...r.kernel.org>, Jan Beulich <JBeulich@...ell.com>,
	Andi Kleen <ak@....de>
Subject: Re: [Xen-devel] Re: [patch 12/21] Xen-paravirt: Allocate and free
 vmalloc areas

On 16/2/07 19:26, "Jeremy Fitzhardinge" <jeremy@...p.org> wrote:

> Keir Fraser wrote:
>> Hmmm... Actually looks like a bunch of architectures do lazy sync of the
>> vmalloc area, although neither ia64 nor powerpc does so. However, all
>> current users of the alloc_vm_area() function would be okay since none of
>> the other lazy-syncing architectures are supported by Xen.
>>   
> 
> Well, assuming that alloc_vm_area() has some non-Xen use, the right
> thing is for archs to export vmalloc_sync_all(), and just use that from
> common code.

It has no other users right now and get_vm_area_sync() would be a
better-named and more generically useful function than alloc_vm_area(). But
yes, to be done properly it does require vmalloc_sync_all() to be defined by
all architectures (even if that's BUG() and implement-properly-on-demand).

get_vm_area_sync(), partnered with existing remove_vm_area(), just seems
much smaller and neater than adding four new functions with a more complex
usage: alloc_vm_area, {lock,unlock}_vm_area, and free_vm_area. Maybe keeping
free_vm_area() too makes sense as its interface is more neatly symmetrical
to that of get_vm_area().

 -- Keir

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