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xen-devel
[Xen-devel] Re: [patch 06/26] Xen-paravirt_ops: paravirt_ops: allocate a
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To: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
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Subject: |
[Xen-devel] Re: [patch 06/26] Xen-paravirt_ops: paravirt_ops: allocate a fixmap slot |
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From: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
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Date: |
Tue, 27 Feb 2007 16:49:53 -0800 |
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Cc: |
Zachary Amsden <zach@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Andi Kleen <ak@xxxxxx>, Rusty Russell <rusty@xxxxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, Chris Wright <chrisw@xxxxxxxxxxxx>, virtualization@xxxxxxxxxxxxxx, Ingo Molnar <mingo@xxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> |
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Tue, 27 Feb 2007 16:49:31 -0800 |
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Jeremy Fitzhardinge wrote:
> Ingo Molnar wrote:
>
>> 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.
Hm, this is a bit awkward. We need to map the shared info page fairly
early - say, around paging_init - but we're still on the bootmem
allocator at that point, so get_vm_area isn't usable yet. Using a
fixmap keeps things simple. It seems to me that having a single fixmap
available is useful for this kind of simple/early mapping, and if
someone needs to map something larger, then they can put it off until
get_vm_area() is available...
J
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