Hi Igor, Daniel: Thanks for the hints!
In the PXB doc (https://github.com/qemu/qemu/blob/master/docs/pci_expander_bridge.txt), PXB device internally adds a pci bridge, according to the impl brief: ``` The PXB is composed by: ... - 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. ``` A PXB device already takes 2 bus nr: 1 for the added root bus via host bridge, 1 for the pci bridge. If statically adding 1 more pci bridge, it takes 1 more pci bus... Anyway, will try to figure out the reason why the doc says "Using the bridge will enable hotplug support", but in fact not :-) The start point seemingly is, to generate correct ACPI SSDT table having hotplug devices/methods for slots behind the PXB internal pci bridge. Regards, Eric Ren On Fri, 22 Apr 2022 at 16:57, Igor Mammedov <imamm...@redhat.com> wrote: > > On Fri, 22 Apr 2022 09:29:20 +0100 > Daniel P. Berrangé <berra...@redhat.com> wrote: > > > On Fri, Apr 22, 2022 at 03:17:11PM +0800, Eric Ren wrote: > > > Hi Marcel and all, > > > > > > It fails when I want to hotplug device to PXB bus. Then, I find this > > > commit that explicitely declares the fact that PXB bus does not support > > > hotplug device onto it. > > > > > > 7b346c742cd9 ("hw/pxb: declare pxb devices as not hot-pluggable") > > > > > > Could you please help confirm the possibility to make PXB bus > > > hotpluggable, > > > and the main work to achieve it if possible? > > > > Instead of trying to hotplug into the PXB, attach a 'pci-bridge' to the > > PXB and then you can hotplug into the latter instead. > > there is no ACPI based hotplug for devices on pxb if I'm not mistaken, so > you'll likely need to enable shpc on pci-bridge. > > > > Yes, pxb-pcie with Q35 do support hotplug, but we use i440 machine a long > > > way, > > > not willing to change machine type to have it. > > > > With regards, > > Daniel > -- - Eric Ren
