On Mon, Nov 19, 2012 at 05:34:12PM +0100, Alexander Graf wrote:
>
> On 13.11.2012, at 03:47, David Gibson wrote:
>
> > From: Alexey Kardashevskiy <[email protected]>
> >
> > In future (with VFIO) we will have multiple PCI host bridges on
> > pseries. Each one needs a unique LIOBN (IOMMU id). At the moment we
> > derive these from the pci domain number, but the whole notion of
> > domain numbers on the qemu side is bogus and in any case they're not
> > actually uniquely allocated at this point.
> >
> > This patch, therefore uses a simple sequence counter to generate
> > unique LIOBNs for PCI host bridges.
> >
> > Signed-off-by: Alexey Kardashevskiy <[email protected]>
> > Signed-off-by: David Gibson <[email protected]>
>
> I don't really like the idea of having a global variable just
> because our domain ID generation seems to not work as
> expected. Michael, any comments here?
Well, the patch I sent which changed domain id generation was
ignored. In any case, as I said, the whole concept of domain numbers
makes no sense on the qemu side, so I don't think increasing reliance
on them by using them here is a good idea.
It would be conceptually nicer to derive the liobn from the buid, but
that would rely on the buid's being unique in the low 32-bits, which
is true in practice, but seems risky to rely on.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
