From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37332) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YXTxN-0000f3-HK for qemu-devel@nongnu.org; Mon, 16 Mar 2015 08:17:21 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YXTxM-0005PM-7D for qemu-devel@nongnu.org; Mon, 16 Mar 2015 08:17:17 -0400 Message-ID: <5506C9A8.5050001@redhat.com> Date: Mon, 16 Mar 2015 14:16:40 +0200 From: Marcel Apfelbaum MIME-Version: 1.0 References: <1426001534-7151-1-git-send-email-marcel@redhat.com> <1426001534-7151-29-git-send-email-marcel@redhat.com> <20150310164449-mutt-send-email-mst@redhat.com> <54FF19FA.8040808@redhat.com> <20150310184149-mutt-send-email-mst@redhat.com> In-Reply-To: <20150310184149-mutt-send-email-mst@redhat.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v5 for-2.3 28/28] docs: Add PXB documentation List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: kraxel@redhat.com, quintela@redhat.com, seabios@seabios.org, qemu-devel@nongnu.org, agraf@suse.de, alex.williamson@redhat.com, kevin@koconnor.net, qemu-ppc@nongnu.org, hare@suse.de, imammedo@redhat.com, amit.shah@redhat.com, pbonzini@redhat.com, leon.alrae@imgtec.com, aurelien@aurel32.net, rth@twiddle.net On 03/10/2015 07:42 PM, Michael S. Tsirkin wrote: > On Tue, Mar 10, 2015 at 06:21:14PM +0200, Marcel Apfelbaum wrote: >> On 03/10/2015 05:47 PM, Michael S. Tsirkin wrote: >>> On Tue, Mar 10, 2015 at 05:32:14PM +0200, Marcel Apfelbaum wrote: >>>> Signed-off-by: Marcel Apfelbaum >>>> --- >>>> docs/pci_expander_bridge.txt | 52 ++++++++++++++++++++++++++++++++++++++++++++ >>>> 1 file changed, 52 insertions(+) >>>> create mode 100644 docs/pci_expander_bridge.txt >>>> >>>> diff --git a/docs/pci_expander_bridge.txt b/docs/pci_expander_bridge.txt >>>> new file mode 100644 >>>> index 0000000..58bf7a8 >>>> --- /dev/null >>>> +++ b/docs/pci_expander_bridge.txt >>>> @@ -0,0 +1,52 @@ >>>> +PCI EXPANDER BRIDGE (PXB) >>>> +========================= >>>> + >>>> +Description >>>> +=========== >>>> +PXB is a "light-weight" host bridge in the same PCI domain >>>> +as the main host bridge whose purpose is to enable >>>> +the main host bridge to support multiple PCI root buses. >>>> +It is implemented only for i440fx. >>> >>> BTW what makes it i440fx specific? >>> Also, what happens if you try to use it >>> with a different machine type? >> Is is i440fx specific, please look at patch 22/28. >> Also we have a specific check for i440fx, so CRS >> will not be emitted for other machine types. >> >> Thanks, >> Marcel > > In fact it won't work at all. Need to think about it, > maybe we can make it work more generally. > For CRS, should be possible to emit for q35 too? We can make it work, but not on the scope of this series. However, I'll add a IHostBridgeSnoop interface that will make the device work only with associated bus and this will make it less general. Thanks, Marcel > >>> >>>> + >>>> +As opposed to PCI-2-PCI bridge's secondary bus, PXB's bus >>>> +is a primary bus and can be associated with a NUMA node >>>> +(different from the main host bridge) allowing the guest OS >>>> +to recognize the proximity of a pass-through device to >>>> +other resources as RAM and CPUs. >>>> + >>>> +Usage >>>> +===== >>>> +A detailed command line would be: >>>> + >>>> +[qemu-bin + storage options] >>>> +-bios [seabios-dir]/out/bios.bin -L [seabios-dir]/out/ >>>> +-m 2G >>>> +-object memory-backend-ram,size=1024M,policy=bind,host-nodes=0,id=ram-node0 -numa node,nodeid=0,cpus=0,memdev=ram-node0 >>>> +-object memory-backend-ram,size=1024M,policy=interleave,host-nodes=0,id=ram-node1 -numa node,nodeid=1,cpus=1,memdev=ram-node1 >>>> +-device pxb-device,id=bridge1,bus=pci.0,numa_node=1,bus_nr=4 -netdev user,id=nd-device e1000,bus=bridge1,addr=0x4,netdev=nd >>>> +-device pxb-device,id=bridge2,bus=pci.0,numa_node=0,bus_nr=8 -device e1000,bus=bridge2,addr=0x3 >>>> +-device pxb-device,id=bridge3,bus=pci.0,bus_nr=40 -drive if=none,id=drive0,file=[img] -device virtio-blk-pci,drive=drive0,scsi=off,bus=bridge3,addr=1 >>>> + >>>> +Here you have: >>>> + - 2 NUMA nodes for the guest, 0 and 1. (both mapped to the same NUMA node in host, but you can and should put it in different host NUMA nodes) >>>> + - a pxb host bridge attached to NUMA 1 with an e1000 behind it >>>> + - a pxb host bridge attached to NUMA 0 with an e1000 behind it >>>> + - a pxb host bridge not attached to any NUMA with a hard drive behind it. >>>> + >>>> +Implementation >>>> +============== >>>> +The PXB is composed by: >>>> +- HostBridge (TYPE_PXB_HOST) >>>> + The host bridge allows to register and query the PXB's rPCI root bus in QEMU. >>>> +- PXBDev(TYPE_PXB_DEVICE) >>>> + It is a regular PCI Device that resides on the piix host-bridge bus and its bus uses the same PCI domain. >>>> + However, the bus behind is exposed through ACPI as a primary PCI bus and starts a new PCI hierarchy. >>>> + The interrupts from devices behind the PXB are routed through this device the same as if it were a >>>> + PCI-2-PCI bridge. The _PRT follows the i440fx model. >>>> +- PCIBridgeDev(TYPE_PCI_BRIDGE_DEV) >>>> + Created automatically as part of init sequence. >>>> + When adding a device to PXB it is attached to the bridge for two reasons: >>>> + - Using the bridge will enable hotplug support >>>> + - All the devices behind the bridge will use bridge's IO/MEM windows compacting >>>> + the PCI address space. >>>> + >>>> -- >>>> 2.1.0