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

[Derek Murray <Derek.Murray@xxxxxxxxxxxx>]

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.
Regards,

Derek.



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