Re: [Qemu-devel] [RFC] pxb: Restrict to x86

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Jan 06, 2017 at 08:13:11AM +0200, Marcel Apfelbaum wrote:
> On 01/06/2017 07:04 AM, David Gibson wrote:
> > The PCI Expander Bridge (PXB) device is essentially a hack to allow
> > different PCIe devices to be assigned to different NUMA nodes on x86.  Each
> > PXB is sort-of a separate PCI host bridge, except that its config space
> > is shared with the config space of the main PCI host bridge, rather than
> > being independent.
> > 
> 
> Hi David,
> 
> > This is only necessary if the platform doesn't (easily) allow truly
> > independent PCI host bridges.  AFAIK that's just x86.
> > 
> 
> Indeed, it is possible to support independent PCI host bridges on x86 by
> using a separate MMCONFIG space for each one and enable separate PCI domains.
> We simply didn't need this until now, but maybe will be implemented it in the future.

In fact I would say that's the cleanest way to do this on q35.

> > This patch makes it possible to configure PXB out of the build, and adjusts
> > the default configs so it's only included on x86 targets.
> > 
> 
> Makes sense
> 
> Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>
> 
> Thanks,
> Marcel
> 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  default-configs/i386-softmmu.mak   | 1 +
> >  default-configs/x86_64-softmmu.mak | 1 +
> >  hw/pci-bridge/Makefile.objs        | 2 +-
> >  3 files changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/default-configs/i386-softmmu.mak b/default-configs/i386-softmmu.mak
> > index 0b51360..6c52d26 100644
> > --- a/default-configs/i386-softmmu.mak
> > +++ b/default-configs/i386-softmmu.mak
> > @@ -56,3 +56,4 @@ CONFIG_IOH3420=y
> >  CONFIG_I82801B11=y
> >  CONFIG_SMBIOS=y
> >  CONFIG_HYPERV_TESTDEV=$(CONFIG_KVM)
> > +CONFIG_PXB=y
> > diff --git a/default-configs/x86_64-softmmu.mak b/default-configs/x86_64-softmmu.mak
> > index 7f89503..2d0341c 100644
> > --- a/default-configs/x86_64-softmmu.mak
> > +++ b/default-configs/x86_64-softmmu.mak
> > @@ -56,3 +56,4 @@ CONFIG_IOH3420=y
> >  CONFIG_I82801B11=y
> >  CONFIG_SMBIOS=y
> >  CONFIG_HYPERV_TESTDEV=$(CONFIG_KVM)
> > +CONFIG_PXB=y
> > diff --git a/hw/pci-bridge/Makefile.objs b/hw/pci-bridge/Makefile.objs
> > index f2adfe3..5612bd7 100644
> > --- a/hw/pci-bridge/Makefile.objs
> > +++ b/hw/pci-bridge/Makefile.objs
> > @@ -1,5 +1,5 @@
> >  common-obj-y += pci_bridge_dev.o
> > -common-obj-y += pci_expander_bridge.o
> > +common-obj-$(CONFIG_PXB) += pci_expander_bridge.o
> >  common-obj-$(CONFIG_XIO3130) += xio3130_upstream.o xio3130_downstream.o
> >  common-obj-$(CONFIG_IOH3420) += ioh3420.o
> >  common-obj-$(CONFIG_I82801B11) += i82801b11.o
> >