Re: [Qemu-devel] [RFC PATCH 0/2] Allow RedHat PCI bridges reserve more buses than necessary during init

[Alexander Bezzubikov]

ср, 19 июля 2017 г. в 16:57, Konrad Rzeszutek Wilk <address@hidden>:

> 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?

>
> >
> > 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