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

From: Marcel Apfelbaum
Subject: Re: [Qemu-devel] [RFC] pxb: Restrict to x86
Date: Fri, 6 Jan 2017 08:26:25 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1

On 01/06/2017 08:13 AM, 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 

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

Actually ACPI based ARM guests may be able to use the PXB as well,
let's wait for their opinion.


Reviewed-by: Marcel Apfelbaum <address@hidden>


Signed-off-by: David Gibson <address@hidden>
 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
diff --git a/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
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

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