From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33525) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YVMuk-0000HU-CD for qemu-devel@nongnu.org; Tue, 10 Mar 2015 12:21:51 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YVMuj-00040e-8I for qemu-devel@nongnu.org; Tue, 10 Mar 2015 12:21:50 -0400 Message-ID: <54FF19FA.8040808@redhat.com> Date: Tue, 10 Mar 2015 18:21:14 +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> In-Reply-To: <20150310164449-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 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 > >> + >> +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