Re: [PATCH v4 03/10] PCI: Allow per function PCI slots
From: Benjamin Block <hidden>
Date: 2025-10-01 14:34:18
Also in:
kvm, linux-pci, lkml, stable
On Wed, Sep 24, 2025 at 10:16:21AM -0700, Farhan Ali wrote:
On s390 systems, which use a machine level hypervisor, PCI devices are
always accessed through a form of PCI pass-through which fundamentally
operates on a per PCI function granularity. This is also reflected in the
s390 PCI hotplug driver which creates hotplug slots for individual PCI
functions. Its reset_slot() function, which is a wrapper for
zpci_hot_reset_device(), thus also resets individual functions.
Currently, the kernel's PCI_SLOT() macro assigns the same pci_slot object
to multifunction devices. This approach worked fine on s390 systems that
only exposed virtual functions as individual PCI domains to the operating
system. Since commit 44510d6fa0c0 ("s390/pci: Handling multifunctions")
s390 supports exposing the topology of multifunction PCI devices by
grouping them in a shared PCI domain. When attempting to reset a function
through the hotplug driver, the shared slot assignment causes the wrong
function to be reset instead of the intended one. It also leaks memory as
we do create a pci_slot object for the function, but don't correctly free
it in pci_slot_release().
Add a flag for struct pci_slot to allow per function PCI slots for
functions managed through a hypervisor, which exposes individual PCI
functions while retaining the topology.
Fixes: 44510d6fa0c0 ("s390/pci: Handling multifunctions")
Cc: <redacted>
Suggested-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
---
drivers/pci/hotplug/s390_pci_hpc.c | 10 ++++++++--
drivers/pci/pci.c | 5 +++--
drivers/pci/slot.c | 14 +++++++++++---
include/linux/pci.h | 1 +
4 files changed, 23 insertions(+), 7 deletions(-)Looks good to me; thanks. Reviewed-by: Benjamin Block <redacted> -- Best Regards, Benjamin Block / Linux on IBM Z Kernel Development IBM Deutschland Research & Development GmbH / https://www.ibm.com/privacy Vors. Aufs.-R.: Wolfgang Wendt / Geschäftsführung: David Faller Sitz der Ges.: Böblingen / Registergericht: AmtsG Stuttgart, HRB 243294