PCI: s390: Expose the UID as an arch specific PCI slot attribute

On s390, an individual PCI function can generally be identified by two
identifiers, the FID and the UID. Which identifier is used depends on
the scope and the platform configuration.

The first identifier, the FID, is always available and identifies a PCI
device uniquely within a machine. The FID may be virtualized by
hypervisors, but on the LPAR level, the machine scope makes it
impossible to create the same configuration based on FIDs on two
different LPARs of the same machine, and difficult to reuse across
machines.

Such matching LPAR configurations are useful, though, allowing
standardized setups and booting a Linux installation on different LPARs.
To this end the UID, or user-defined identifier, was introduced. While
it is only guaranteed to be unique within an LPAR and only if indicated
by firmware, it allows users to replicate PCI device setups.

On s390, which uses a machine hypervisor, a per PCI function hotplug
model is used. The shortcoming with the UID then is, that it is not
visible to the user without first attaching the PCI function and
accessing the "uid" device attribute. The FID, on the other hand, is
used as the slot name and is thus known even with the PCI function in
standby.

Remedy this shortcoming by providing the UID as an attribute on the slot
allowing the user to identify a PCI function based on the UID without
having to first attach it. Do this via a macro mechanism analogous to
what was introduced by commit 265baca69a07 ("s390/pci: Stop usurping
pdev->dev.groups") for the PCI device attributes.

Reviewed-by: Gerd Bayer <gbayer@linux.ibm.com>
Reviewed-by: Julian Ruess <julianr@linux.ibm.com>
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com> # drivers/pci/slot.c
Link: https://lore.kernel.org/r/20260407-uid_slot-v8-2-15ae4409d2ce@linux.ibm.com
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

authored by

Niklas Schnelle and committed by

Vasily Gorbik 3 weeks ago e4f9ab03 737c4f4a

+43 -1

4 changed files

expand all

Documentation

arch

s390

pci.rst

arch

s390

include

asm

pci.h

pci

pci_sysfs.c

drivers

pci

slot.c

Documentation/arch/s390/pci.rst

··· 58 58 59 59 - /sys/bus/pci/slots/XXXXXXXX/power 60 60 61 + In addition to using the FID as the name of the slot, the slot directory 62 + also contains the following s390-specific slot attributes. 63 + 64 + - uid: 65 + The User-defined identifier (UID) of the function which may be configured 66 + by this slot. See also the corresponding attribute of the device. 67 + 61 68 A physical function that currently supports a virtual function cannot be 62 69 powered off until all virtual functions are removed with: 63 70 echo 0 > /sys/bus/pci/devices/DDDD:BB:dd.f/sriov_numvf

arch/s390/include/asm/pci.h

··· 208 208 &pfip_attr_group, \ 209 209 &zpci_ident_attr_group, 210 210 211 + extern const struct attribute_group zpci_slot_attr_group; 212 + 213 + #define ARCH_PCI_SLOT_GROUPS (&zpci_slot_attr_group) 214 + 211 215 extern unsigned int s390_pci_force_floating __initdata; 212 216 extern unsigned int s390_pci_no_rid; 213 217

+20

arch/s390/pci/pci_sysfs.c

··· 187 187 } 188 188 static DEVICE_ATTR_RO(index); 189 189 190 + static ssize_t zpci_uid_slot_show(struct pci_slot *slot, char *buf) 191 + { 192 + struct zpci_dev *zdev = container_of(slot->hotplug, struct zpci_dev, 193 + hotplug_slot); 194 + 195 + return sysfs_emit(buf, "0x%x\n", zdev->uid); 196 + } 197 + 198 + static struct pci_slot_attribute zpci_slot_attr_uid = 199 + __ATTR(uid, 0444, zpci_uid_slot_show, NULL); 200 + 190 201 static umode_t zpci_index_is_visible(struct kobject *kobj, 191 202 struct attribute *attr, int n) 192 203 { ··· 252 241 const struct attribute_group pfip_attr_group = { 253 242 .name = "pfip", 254 243 .attrs = pfip_attrs, 244 + }; 245 + 246 + static struct attribute *zpci_slot_attrs[] = { 247 + &zpci_slot_attr_uid.attr, 248 + NULL, 249 + }; 250 + 251 + const struct attribute_group zpci_slot_attr_group = { 252 + .attrs = zpci_slot_attrs, 255 253 }; 256 254 257 255 static struct attribute *clp_fw_attrs[] = {

+12 -1

drivers/pci/slot.c

··· 96 96 &pci_slot_attr_cur_speed.attr, 97 97 NULL, 98 98 }; 99 - ATTRIBUTE_GROUPS(pci_slot_default); 99 + 100 + static const struct attribute_group pci_slot_default_group = { 101 + .attrs = pci_slot_default_attrs, 102 + }; 103 + 104 + static const struct attribute_group *pci_slot_default_groups[] = { 105 + &pci_slot_default_group, 106 + #ifdef ARCH_PCI_SLOT_GROUPS 107 + ARCH_PCI_SLOT_GROUPS, 108 + #endif 109 + NULL, 110 + }; 100 111 101 112 static const struct kobj_type pci_slot_ktype = { 102 113 .sysfs_ops = &pci_slot_sysfs_ops,

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