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

To: Keir Fraser <keir@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [RFC] [0/4] User-space grants for Console and XenStore
From: Derek Murray <Derek.Murray@xxxxxxxxxxxx>
Date: Wed, 2 May 2007 16:33:22 +0100
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On 2 May 2007, at 15:48, Keir Fraser wrote:

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.

Not quite so bad - the current keys are called "ring-ref", so I'll probably add "ring-grant-ref" for the new entries.

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.

It's even simpler in practice. If the gntdev isn't available, then xc_gnttab_open() will fail (as long as there's a stub in the Solaris version of libxc), so there will be no "xcg" handle with which to try to map the grant reference. Therefore we can go straight to the direct map method. I suppose, in addition, if we do have an xcg handle and the grant mapping fails for some reason, we could still fall back to the direct map method, though this failure should definitely be noted.



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