Re: pcie hotplug driver probe is not getting called

[Bjorn Helgaas <helgaas@kernel.org>]

On Sun, Sep 29, 2024 at 07:29:32PM +0530, Maverickk 78 wrote:
> Hi Bjorn,
> 
> I have a switch connecting to the Host bridge, one of the downstream
> port(02:1.0) on the switch has the slot enabled.
> 
> Appended pcie_ports=native along with pciehp.pciehp_force=1
> pciehp.pciehp_debug=1  to the cmdline and I see the driver creating symlink
> to sysfs device node.
> 
> Does this mean pciehp can handle the hotplug events? asking this because
> none of the functions in pciehp_core listed in ftrace?

From the dmesg log you attached:

  [    0.000000] DMI: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-0-g155821a-20210629_105355-sharpie 04/01/2014
  [    0.000000] Hypervisor detected: KVM
  [    0.408755] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-6.11.0+ root=UUID=f563804b-1b93-4921-90e1-4114c8111e8f ro modprobe.blacklist=mpt3sas ftrace=function_graph ftrace_graph_filter=*pcie* pciehp.pciehp_force=1 pciehp.pciehp_debug=1 pcie_ports=native quite splash crashkernel=512M-:192M vt.handoff=7
  [    1.640055] acpiphp: ACPI Hot Plug PCI Controller Driver version: 0.5
  [    1.736168] acpi PNP0A08:00: _OSC: platform does not support [PCIeHotplug LTR DPC]
  [    1.738096] acpi PNP0A08:00: _OSC: OS now controls [SHPCHotplug PME AER PCIeCapability]
  [    9.885390] pcieport 0000:02:01.0: pciehp: Slot #0 AttnBtn+ PwrCtrl+ MRL+ AttnInd+ PwrInd+ HotPlug+ Surprise+ Interlock- NoCompl- IbPresDis- LLActRep+

I assume this kernel is running as a KVM guest.  The firmware _OSC
says the platform (QEMU) doesn't support native PCIe hotplug, so
host->native_pcie_hotplug will be false.  But of course
"pcie_ports=native" would set pcie_ports_native, so the portdrv
get_port_device_capability() will set PCIE_PORT_SERVICE_HP, which
allows pciehp to bind to 02:01.0.

The "pcieport 0000:02:01.0: pciehp: Slot #0" line shows that
pciehp_probe() was called.

I don't know whether QEMU supports PCIe hotplug interrupts though.

When do you expect pciehp to do something?  Are you hotplugging a
physical device that is passed through to this guest?

Bjorn