2017-07-19 21:18 GMT+03:00 Konrad Rzeszutek Wilk <konrad.w...@oracle.com>:
> On Wed, Jul 19, 2017 at 05:14:41PM +0000, Alexander Bezzubikov wrote: > > ср, 19 июля 2017 г. в 16:57, Konrad Rzeszutek Wilk < > konrad.w...@oracle.com>: > > > > > On Wed, Jul 19, 2017 at 04:20:12PM +0300, Aleksandr Bezzubikov wrote: > > > > Now PCI bridges (and PCIE root port too) get a bus range number in > > > system init, > > > > basing on currently plugged devices. That's why when one wants to > > > hotplug another bridge, > > > > it needs his child bus, which the parent is unable to provide. > > > > > > Could you explain how you trigger this? > > > > > > I'm trying to hot plug pcie-pci bridge into pcie root port, and Linux > says > > 'cannot allocate bus number for device bla-bla'. This obviously does not > > allow me to use the bridge at all. > > > > > > > > > > > > The suggested workaround is to have vendor-specific capability in > RedHat > > > generic pcie-root-port > > > > that contains number of additional bus to reserve on BIOS PCI init. > > > > > > But wouldn't the proper fix be for the PCI bridge to have the > subordinate > > > value be extended to fit more bus ranges? > > > > > > What do you mean? This is what I'm trying to do. Do you suppose to get > rid > > of vendor-specific cap and use original register value instead of it? > > I would suggest a simple fix - each bridge has a a number of bus devices > it can use. You have up to 255 - so you split the number of northbridge > numbers by the amount of NUMA nodes (if that is used) - so for example > if you have 4 NUMA nodes, each bridge would cover 63 bus numbers. > > Meaning the root bridge would cover 0->63 bus, 64->128, and so on. > That gives you enough space to plug in your plugged in devices > (up to 63). > > And if you need sub-briges then carve out a specific range. > The problem is that we don't know at the init moment how many subbridges we may need, and how deep the whole device tree will be. The key moment - PCI bridge hotplugging needs either rescan all buses on each bridge device addition, or reserve space in advance during BIOS init. In this series the second way was chosen. > > > > > > > > > > > > > > > Aleksandr Bezzubikov (2): > > > > pci: add support for direct usage of bdf for capability lookup > > > > pci: enable RedHat pci bridges to reserve more buses > > > > > > > > src/fw/pciinit.c | 12 ++++++++++-- > > > > src/hw/pcidevice.c | 24 ++++++++++++++++++++++++ > > > > src/hw/pcidevice.h | 1 + > > > > 3 files changed, 35 insertions(+), 2 deletions(-) > > > > > > > > -- > > > > 2.7.4 > > > > > > > > > > > > > -- > > Alexander Bezzubikov > -- Alexander Bezzubikov
