On 21.11.2012, at 06:00, David Gibson <da...@gibson.dropbear.id.au> wrote:
> On Tue, Nov 20, 2012 at 10:27:11AM +0100, Alexander Graf wrote: >> >> On 19.11.2012, at 23:51, David Gibson wrote: >> >>> 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 <a...@ozlabs.ru> >>>>> >>>>> 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 <a...@ozlabs.ru> >>>>> Signed-off-by: David Gibson <da...@gibson.dropbear.id.au> >>>> >>>> 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 >> >> Michael? >> >>> 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. >> >> Well, there has to be some uniqueness from the guest's POV already, >> no? > > Yes, the BUIDs are unique, but they are 64-bit, whereas the LIOBN is > only 32-bit. Tricky. Michael, any ideas? Alex > > -- > 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
