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Re: [Xen-devel] [PATCH] Paravirt framebuffer frontend kernel support [1/

To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] Paravirt framebuffer frontend kernel support [1/5]
From: Markus Armbruster <armbru@xxxxxxxxxx>
Date: Thu, 21 Sep 2006 20:41:13 +0200
Cc: Jeremy Katz <katzj@xxxxxxxxxx>, aliguori <aliguori@xxxxxxxxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, sos22@xxxxxxxxxxxxx
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In-reply-to: <C124AE2E.23E8%Keir.Fraser@xxxxxxxxxxxx> (Keir Fraser's message of "Wed, 06 Sep 2006 16:56:14 +0100")
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Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> writes:

> On 6/9/06 10:11 am, "Steven Smith" <sos22-xen@xxxxxxxxxxxxx> wrote:
>>> I wouldn't complain if we go the route Keir suggested and have Xen do
>>> it ;-)  But if not, I think that given the size of the memory in
>>> question + grant tables, the quick hack is probably going to be the
>>> "right" thing for this case.

The quick hack being translating mfns in the backend.

>> Okay.  Adding translations to the hypervisor isn't going to happen
>> until after 3.0.3, so we should probably just leave this for a little
>> while.
> Another option after 3.0.3 is to allow grant tables to support these large
> mappings. I have some ideas how to do this fairly efficiently, given that
> it'll be okay to track mappings to all the pages as an aggregate. It's not
> going to happen for now though -- it'll just be a shame if we add
> grant-table support later that it'll change the setup protocol. However, we
> can probably maintain backward compatibility if we think about it a bit.
>  -- Keir

Is there anything we can do now to help with maintaining backward
compatibility later?

Evolving interfaces are a fact of life.  What about versioning?
Frontend puts its interface version in xenstore, bump it when we
change stuff (which should happen very rarely, of course), backend
queries the version and does the right thing.

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