linux-kernel - Re: [patch 06/26] Xen-paravirt_ops: paravirt

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Message-ID: <45E47E95.2060803@goop.org>
Date:	Tue, 27 Feb 2007 10:55:17 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Andi Kleen <ak@....de>, Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, virtualization@...ts.osdl.org,
	xen-devel@...ts.xensource.com, Chris Wright <chrisw@...s-sol.org>,
	Zachary Amsden <zach@...are.com>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [patch 06/26] Xen-paravirt_ops: paravirt_ops: allocate a fixmap
 slot

Ingo Molnar wrote:
> * Jeremy Fitzhardinge <jeremy@...p.org> wrote:
>
>   
>> Allocate a fixmap slot for use by a paravirt_ops implementation.  Xen 
>> uses this to map the hypervisor's shared info page, which doesn't have 
>> a pseudo-physical page number, and therefore can't be mapped 
>> ordinarily.
>>     
>
> why not vmalloc it on the guest side? fixmaps are bad for this purpose 
> for a general paravirt implementation, it limits the size of the shared 
> info page, etc.

Yes.  vmalloc would have the annoying side-effect of actually allocating
some pages which would be shadowed by the remapping, but I guess
get_vm_area would do the job.  I'll give it a go.

    J
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