On Sun, Apr 15, 2012 at 09:47:47PM +1000, David Gibson wrote: > On Sun, Apr 15, 2012 at 01:03:57PM +0300, Michael S. Tsirkin wrote: > > On Mon, Apr 02, 2012 at 02:17:36PM +1000, David Gibson wrote: > > > Currently the pseries PCI code uses a somewhat strange scheme of PCI irq > > > allocation - one per slot up to a maximum that's greater than the usual 4. > > > This scheme more or less worked, because we were able to tell the guest > > > the > > > irq mapping in the device tree, however it's nonstandard and may break > > > assumptions in the future. Worse, the array used to construct the dev > > > tree interrupt map was mis-sized, we got away with it only because it > > > happened that our SPAPR_PCI_NUM_LSI value was greater than 7. > > > > > > This patch changes the pseries PCI code to use the normal PCI interrupt > > > swizzling scheme instead, > > > > I don't see anything wrong with the code - I assume someone > > who applies this knows about real hardware and can check that > > it behaves as emulated here. > > Because the device tree lets us advertise to the guest precisely how > the interrupts are mapped, it doesn't really matter whether we behave > identically to "real" hardware (the PAPR platform we're emulating here > is already a para-virtualized environment running under a hypervisor, > so "real" isn't a particularly clear concept). I'm not sure if all > pseries machines (and/or hypervisor versions) are the same in this > regard, but the new scheme is certainly in use. As long as the device > tree has the correct information, really any interrupt mapping scheme > is compliant with PAPR.
So no need to check that then :) > > But I don't remember any standard scheme except for bridge devices, > > and this isn't one, is it? Care to clarify? > > Well, the standard swizzling scheme is for p2p bridges, whereas this > is a host bridge, but there's no reason not to use the same scheme for > both. This will become more important when we implement pass-through. > On pSeries the unit of passthrough can be either a host bridge or a > p2p bridge, and having the same swizzling scheme will make life > easier. So the comment 'use standard PCI swizzling' misleads in implying the motivation is the standard. Better remove it, or replace with real motivation. > Plus this scheme is basically just better - it won't force > all the functions of a multi-function device to share an interrupt. Only if some functions use pin != INTA. Maybe it's true for pseries? On the pc most of them use INTA. > -- > 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
