Re: [Xen-devel] extending blkif_request_t

[Mark Williamson <maw48@xxxxxxxxxxxx>]

> If you need to add a new field to blkif_request_t, you might have to be
> very careful, because the size of blkif_request_t and the blkif_ring_t are
> carefully calibrated. If you add a new field, make it sure that the size
> of blkif_ring_t will not exceed PAGE_SIZE. You may also change
> blkif_ring_t to hold more request. That may take some more work.

Under the unstable tree it'll automatically sort itself out, since the blkif 
drivers use the magic ring macros in xen/include/public/io/ring.h - in that 
tree, the netif drivers are the only ones that don't use these ring macros at 
the moment.

Under the 2.0.x tree, you'll still have to sort out ring sizing issues 
manually.

When playing with these structures, don't forget to recompile both front and 
backend kernels, or things will get very confused!

Cheers,
Mark

> Good luck,
> Xin
>
> On Sat, 19 Mar 2005, Deepak Manohar wrote:
> > Hi,
> >
> >  I am sorry if this was asked earlier, but I couldnt find it.
> >
> >  If I want to pass another field in the structure blkif_request_t do I
> > simply add it to xen/include/public/io/blkif.h ?
> >
> >  After doing this will the backend and the frontend be able to access
> > this field. Thanks.
> >
> > Deepak
> >
> >
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