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: stable@vger.kernel.org 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 bblock@linux.ibm.com