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

[Keir Fraser <keir@xxxxxxxxxxxxx>]

On 19/1/07 15:08, "Gerd Hoffmann" <kraxel@xxxxxxx> wrote:

>> And magic numbers
>> suck compared with intelligible strings for this kind of thing imo.
> 
> We'll need both then.  Strings are certainly nice for human-visible
> stuff, but you don't want to strcmp() all the time in the backend.
> Wouldn't be a problem for pvfb, but for blkfront/back where the ring
> protocol is abi-dependent and thus the backend has to check often.

You missed out the patch. I'm sure however that I'll argue you should make
the enumeration local to the backend. It will always support his native
architecture. Where it supports cross-architecture (i386-on-x64) he can
*privately* have a numeric assignment for that situation which it uses on
data paths. Then we don't have redundant info in xenstore and we don't get
tied to particular magic numbers.

But I definitely agree that a private enumeration, or sets of accessor hook
functions, makes sense. We'll certainly need one or the other for
efficiency.

 -- Keir


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