On Wed, Nov 21, 2012 at 11:36:00PM +1100, David Gibson wrote: > On Wed, Nov 21, 2012 at 01:34:48PM +0200, Michael S. Tsirkin wrote: > > On Wed, Nov 21, 2012 at 11:57:05AM +1100, David Gibson wrote: > > > On Tue, Nov 20, 2012 at 02:26:09PM +0200, Michael S. Tsirkin 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? > > > > > > > > This is user visible, right? > > > > So IMHO we should have the user specify LIOBN through a property, > > > > rather than assign what's essentially a random value. > > > > > > Well, I can implement an override through a property, which could be > > > useful in some circumstances. But we still need to have qemu generate > > > unique defaults, rather than forcing it to be specified in every case. > > > > I don't see why. > > And if you want automatic defaults then they need to be generated in a > > way that does not depend on implementation detail such as order of > > device initialization. > > Because requiring explicit unique liobns to be supplied whenever there > is more than one PHB is horrible for usability.
We should make simple things simple and complex things possible. More than one PHB seems like an advanced feature so I don't see why it needs to be made very easy to use. With an appropriate error message it should not be too hard for users to figure it out. > -- > 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
