Re: [Xen-devel] 32-on-64: pvfb issue

[Keir Fraser <keir@xxxxxxxxxxxxx>]

On 19/1/07 12:59, "Gerd Hoffmann" <kraxel@xxxxxxx> wrote:

>> Right now, since we make no
>> effort to ensure protocol compat across machine architectures (for example
>> we use native endianness) I suggest that we define a per-architecture
>> protocol name: 'x86_32', 'x86_64', 'ia64', 'powerpc64', etc.
> 
> Hmm, not sure I like that idea, especially for pvfb as there certainly
> will come the protocol switch to grant tables, so using the arch names
> doesn't sound like a good idea to me.

Then we would make the protocol name structural: '<arch>-v2' rather than the
extending an enumeration to 3 and 4 (in your scheme). Or take advantage of
the stringness and call it '<arch>-grant'. Personally I'm of the opinion
that the architectural ABI is a fundamental component of our protocol (in
fact, the very component that is tripping us up here!). And magic numbers
suck compared with intelligible strings for this kind of thing imo. However,
I am open to persuasive arguments on this point. I'm not quite as stuck on
it as I am regarding use of xenbus for this field: it just occurred to me as
a seemingly neat extensible technique. :-)

 -- Keir


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