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Re: [Qemu-trivial] [PATCH] Correctly assign PCI domain numbers
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-trivial] [PATCH] Correctly assign PCI domain numbers |
Date: |
Wed, 3 Aug 2011 13:21:35 +0300 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Wed, Aug 03, 2011 at 11:13:15AM +0100, Stefan Hajnoczi wrote:
> On Mon, Aug 01, 2011 at 01:10:38PM +0300, Michael S. Tsirkin wrote:
> > On Mon, Aug 01, 2011 at 04:51:02PM +1000, David Gibson wrote:
> > > qemu already almost supports PCI domains; that is, several entirely
> > > independent PCI host bridges on the same machine. However, a bug in
> > > pci_bus_new_inplace() means that every host bridge gets assigned domain
> > > number zero and so can't be properly distinguished. This patch fixes the
> > > bug, giving each new host bridge a new domain number.
> > >
> > > Signed-off-by: David Gibson <address@hidden>
> >
> > OK, but I'd like to see the whole picture.
> > How does the guest detect multiple domains,
> > and how does it access them?
> >
> > > ---
> > > hw/pci.c | 5 ++++-
> > > 1 files changed, 4 insertions(+), 1 deletions(-)
> > >
> > > diff --git a/hw/pci.c b/hw/pci.c
> > > index 36db58b..2b4aecb 100644
> > > --- a/hw/pci.c
> > > +++ b/hw/pci.c
> > > @@ -262,6 +262,8 @@ int pci_find_domain(const PCIBus *bus)
> > > return -1;
> > > }
> > >
> > > +static int pci_next_domain; /* = 0 */
> > > +
> > > void pci_bus_new_inplace(PCIBus *bus, DeviceState *parent,
> > > const char *name,
> > > MemoryRegion *address_space,
> > > @@ -274,7 +276,8 @@ void pci_bus_new_inplace(PCIBus *bus, DeviceState
> > > *parent,
> > >
> > > /* host bridge */
> > > QLIST_INIT(&bus->child);
> > > - pci_host_bus_register(0, bus); /* for now only pci domain 0 is
> > > supported */
> > > +
> > > + pci_host_bus_register(pci_next_domain++, bus);
> >
> > What happens when that overflows?
>
> In what scenario do we reach such a high number? (I'm not saying this
> is harmless, just trying to understand if it should be an assert or
> error return.)
>
> Stefan
Can bus ever get hot-plugged?