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Re: [Xen-devel] [RFC] [0/4] User-space grants for Console and XenStore

To: Derek Murray <Derek.Murray@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] [RFC] [0/4] User-space grants for Console and XenStore
From: Keir Fraser <keir@xxxxxxxxxxxxx>
Date: Wed, 02 May 2007 15:48:24 +0100
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Thread-topic: [Xen-devel] [RFC] [0/4] User-space grants for Console and XenStore
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On 2/5/07 15:38, "Derek Murray" <Derek.Murray@xxxxxxxxxxxx> wrote:

> At present, I don't store the grant-refs in xenstore, because they
> are constant (always 0 for xenstore, 1 for the console). I suppose I
> can see an argument where two different tool stacks are used with
> different conventions, but the same console and xenstore daemons are
> used. The tricky part is getting the grant references out of the
> domain builder without changing the interface to xc_linux_build().
> Would it be reasonable to assume that the current versions of xend
> and libxc are consistent, and therefore the fixed grant references
> could be written into xenstore (from constants in the Python code) at
> the same time as the console and xenstore mfns are?

I would accept that degree of binding between libxenctrl.so and the Python
binding Xc.so, yes. The existing xenstore arguments/fields might already be
unhelpfully called grant-ref, by the way. :-) Very stupid of me if so.
You'll just have to be a bit imaginative about naming of new args/fields in
that case.

> This should be quite simple: if the call to xc_gnttab_open() fails,
> it could set a flag which determines the method to be used. All that
> needs to be done in the mean time is to add stub functions to
> xc_solaris.c - I'll do that.

It's as simple as try grant-table method, fall back to direct-map method,
then fail outright, isn't it? Maybe that's what you meant.

 -- Keir

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