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

[Marcel Apfelbaum <marcel.apfelbaum@gmail.com>]

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 future.
>
>> 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.

Thanks,
Marcel

>
> 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
>>
>
>