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

[Keir Fraser <keir@xxxxxxxxxxxxx>]

On 18/1/07 15:35, "Gerd Hoffmann" <kraxel@xxxxxxx> wrote:

>> Excuse my ignorance, but why do you have to guess the guest's size?
>> Doesn't dom0 know?
> 
> No, right now there is no hypercall to get that information.  Which
> brings the discussion back onto the table:  Should we add one?  pvfb
> isn't the only driver with that kind of problems.
> 
> And it better shouldn't be a dom0-only hypercall, otherwise driver
> domains will not be able to use it ...

Do the same as you did with blkback. Add a protocol version or bitwidth
field to xenstore. Update frontend driver to write that field. Make tools
write a default value for pv guests for backward compat. This is even better
than with blkfront/blkback because there are definitely no PV-on-HVM pvfb
driver frontends out in the wild (and it's HVM that makes things harder).

Speaking of which, we should add the protocol/bitwidth field to blkfront
asap...

 -- Keir


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