On Mon, Mar 16, 2015 at 02:16:40PM +0200, Marcel Apfelbaum wrote: > 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 <mar...@redhat.com> > >>>>--- > >>>> 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
OK, this works too. Do you mean PCIHostBridgeSnoop? > > > >>> > >>>>+ > >>>>+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
