* [PATCH 5.10.y 2/3] PCI: Introduce PCI_SLOT_PLACEHOLDER constant for slot_nr placeholder value
2026-09-09 14:53 ` [PATCH 5.10.y 1/3] PCI/sysfs: Rely on lengths from scnprintf(), dsm_label_utf16s_to_utf8s() Sasha Levin
@ 2026-09-09 14:53 ` Sasha Levin
2026-09-09 14:53 ` [PATCH 5.10.y 3/3] PCI: Allow per function PCI slots to fix slot reset on s390 Sasha Levin
1 sibling, 0 replies; 4+ messages in thread
From: Sasha Levin @ 2026-09-09 14:53 UTC (permalink / raw)
To: stable
Cc: Farhan Ali, Bjorn Helgaas, Madhavan Srinivasan, Tyrel Datwyler,
linuxppc-dev, Sasha Levin
From: Farhan Ali <alifm@linux.ibm.com>
[ Upstream commit c243e6c470c4695965cc8287767925bc1d9a7867 ]
Introduce a constant for placeholder value and update the kerneldoc for
pci_create_slot() to reference PCI_SLOT_PLACEHOLDER instead of -1
throughout. No functional change.
Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Tyrel Datwyler <tyreld@linux.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org
Link: https://patch.msgid.link/20260805165518.794-2-alifm@linux.ibm.com
[Backport preparation for dcc5bec09e23 on Linux 5.10]
The stable tree lacks the bus-wide slot support present in the target's
parent. Include PCI_SLOT_ALL_DEVICES and its core matching, address output,
and documentation from 102c8b26b54e, without changing PCIe hotplug callers.
This supplies the context needed for the target's per-function matching
changes while retaining the existing behavior of current callers.
Keep the stable sprintf(), allocation, kobject, and module-link code.
Convert only pci_dev_reset_slot_function()'s existing probe parameter to
bool to match the target's reset hunk; its callers already pass 0 or 1.
No functions are added. Preserve both PowerPC placeholder caller updates
so they remain consistent when the target widens PCI_SLOT_PLACEHOLDER.
Stable-dep-of: dcc5bec09e23 ("PCI: Allow per function PCI slots to fix slot reset on s390")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/pci/hotplug/pnv_php.c | 2 +-
drivers/pci/hotplug/rpaphp_slot.c | 2 +-
drivers/pci/pci.c | 2 +-
drivers/pci/slot.c | 58 ++++++++++++++++++++++---------
include/linux/pci.h | 13 ++++++-
5 files changed, 56 insertions(+), 21 deletions(-)
diff --git a/drivers/pci/hotplug/pnv_php.c b/drivers/pci/hotplug/pnv_php.c
index 03c4d0d7f9b15..325192abb8fd1 100644
--- a/drivers/pci/hotplug/pnv_php.c
+++ b/drivers/pci/hotplug/pnv_php.c
@@ -798,7 +798,7 @@ static struct pnv_php_slot *pnv_php_alloc_slot(struct device_node *dn)
if (dn->child && PCI_DN(dn->child))
php_slot->slot_no = PCI_SLOT(PCI_DN(dn->child)->devfn);
else
- php_slot->slot_no = -1; /* Placeholder slot */
+ php_slot->slot_no = PCI_SLOT_PLACEHOLDER; /* Placeholder slot */
kref_init(&php_slot->kref);
php_slot->state = PNV_PHP_STATE_INITIALIZED;
diff --git a/drivers/pci/hotplug/rpaphp_slot.c b/drivers/pci/hotplug/rpaphp_slot.c
index 93b4a945c55d9..bb20c0800dff4 100644
--- a/drivers/pci/hotplug/rpaphp_slot.c
+++ b/drivers/pci/hotplug/rpaphp_slot.c
@@ -84,7 +84,7 @@ int rpaphp_register_slot(struct slot *slot)
struct device_node *child;
u32 my_index;
int retval;
- int slotno = -1;
+ int slotno = PCI_SLOT_PLACEHOLDER;
dbg("%s registering slot:path[%pOF] index[%x], name[%s] pdomain[%x] type[%d]\n",
__func__, slot->dn, slot->index, slot->name,
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 6658bba9717d7..7d887c299e89b 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4869,7 +4869,7 @@ static int pci_reset_hotplug_slot(struct hotplug_slot *hotplug, int probe)
return rc;
}
-static int pci_dev_reset_slot_function(struct pci_dev *dev, int probe)
+static int pci_dev_reset_slot_function(struct pci_dev *dev, bool probe)
{
if (dev->multifunction || dev->subordinate || !dev->slot ||
dev->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET)
diff --git a/drivers/pci/slot.c b/drivers/pci/slot.c
index a42e2cf774fd8..3a125a8417dca 100644
--- a/drivers/pci/slot.c
+++ b/drivers/pci/slot.c
@@ -38,15 +38,24 @@ static const struct sysfs_ops pci_slot_sysfs_ops = {
static ssize_t address_read_file(struct pci_slot *slot, char *buf)
{
- if (slot->number == 0xff)
+ if (slot->number == PCI_SLOT_PLACEHOLDER)
return sprintf(buf, "%04x:%02x\n",
pci_domain_nr(slot->bus),
slot->bus->number);
- else
- return sprintf(buf, "%04x:%02x:%02x\n",
+
+ /*
+ * Preserve legacy ABI expectations that hotplug drivers that manage
+ * multiple devices per slot emit 0 for the device number.
+ */
+ if (slot->number == PCI_SLOT_ALL_DEVICES)
+ return sprintf(buf, "%04x:%02x:00\n",
pci_domain_nr(slot->bus),
- slot->bus->number,
- slot->number);
+ slot->bus->number);
+
+ return sprintf(buf, "%04x:%02x:%02x\n",
+ pci_domain_nr(slot->bus),
+ slot->bus->number,
+ slot->number);
}
static ssize_t bus_speed_read(enum pci_bus_speed speed, char *buf)
@@ -74,7 +83,8 @@ static void pci_slot_release(struct kobject *kobj)
down_read(&pci_bus_sem);
list_for_each_entry(dev, &slot->bus->devices, bus_list)
- if (PCI_SLOT(dev->devfn) == slot->number)
+ if (slot->number == PCI_SLOT_ALL_DEVICES ||
+ PCI_SLOT(dev->devfn) == slot->number)
dev->slot = NULL;
up_read(&pci_bus_sem);
@@ -166,7 +176,8 @@ void pci_dev_assign_slot(struct pci_dev *dev)
mutex_lock(&pci_slot_mutex);
list_for_each_entry(slot, &dev->bus->slots, list)
- if (PCI_SLOT(dev->devfn) == slot->number)
+ if (slot->number == PCI_SLOT_ALL_DEVICES ||
+ PCI_SLOT(dev->devfn) == slot->number)
dev->slot = slot;
mutex_unlock(&pci_slot_mutex);
}
@@ -188,7 +199,8 @@ static struct pci_slot *get_slot(struct pci_bus *parent, int slot_nr)
/**
* pci_create_slot - create or increment refcount for physical PCI slot
* @parent: struct pci_bus of parent bridge
- * @slot_nr: PCI_SLOT(pci_dev->devfn) or -1 for placeholder
+ * @slot_nr: PCI_SLOT(pci_dev->devfn), PCI_SLOT_PLACEHOLDER for placeholder, or
+ * PCI_SLOT_ALL_DEVICES
* @name: user visible string presented in /sys/bus/pci/slots/<name>
* @hotplug: set if caller is hotplug driver, NULL otherwise
*
@@ -213,15 +225,26 @@ static struct pci_slot *get_slot(struct pci_bus *parent, int slot_nr)
* In most cases, @pci_bus, @slot_nr will be sufficient to uniquely identify
* a slot. There is one notable exception - pSeries (rpaphp), where the
* @slot_nr cannot be determined until a device is actually inserted into
- * the slot. In this scenario, the caller may pass -1 for @slot_nr.
+ * the slot. In this scenario, the caller may pass PCI_SLOT_PLACEHOLDER for @slot_nr.
*
* The following semantics are imposed when the caller passes @slot_nr ==
- * -1. First, we no longer check for an existing %struct pci_slot, as there
- * may be many slots with @slot_nr of -1. The other change in semantics is
- * user-visible, which is the 'address' parameter presented in sysfs will
- * consist solely of a dddd:bb tuple, where dddd is the PCI domain of the
- * %struct pci_bus and bb is the bus number. In other words, the devfn of
- * the 'placeholder' slot will not be displayed.
+ * PCI_SLOT_PLACEHOLDER. First, we no longer check for an existing %struct
+ * pci_slot, as there may be many slots with @slot_nr of
+ * PCI_SLOT_PLACEHOLDER. The other change in semantics is user-visible,
+ * which is the 'address' parameter presented in sysfs will consist solely
+ * of a dddd:bb tuple, where dddd is the PCI domain of the %struct pci_bus
+ * and bb is the bus number. In other words, the devfn of the 'placeholder'
+ * slot will not be displayed.
+ *
+ * Bus-wide slots:
+ * For PCIe hotplug, the physical slot encompasses the entire secondary
+ * bus, not just a single device number. If the device supports ARI and ARI
+ * Forwarding is enabled in the upstream bridge, a multi-function device
+ * may include functions that appear to have several different device
+ * numbers, i.e., PCI_SLOT() values. Pass @slot_nr == PCI_SLOT_ALL_DEVICES
+ * to create a slot that matches all devices on the bus. Unlike placeholder
+ * slots, bus-wide slots go through normal slot lookup and reuse existing
+ * slots if present.
*/
struct pci_slot *pci_create_slot(struct pci_bus *parent, int slot_nr,
const char *name,
@@ -234,7 +257,7 @@ struct pci_slot *pci_create_slot(struct pci_bus *parent, int slot_nr,
mutex_lock(&pci_slot_mutex);
- if (slot_nr == -1)
+ if (slot_nr == PCI_SLOT_PLACEHOLDER)
goto placeholder;
/*
@@ -286,7 +309,8 @@ struct pci_slot *pci_create_slot(struct pci_bus *parent, int slot_nr,
down_read(&pci_bus_sem);
list_for_each_entry(dev, &parent->devices, bus_list)
- if (PCI_SLOT(dev->devfn) == slot_nr)
+ if (slot_nr == PCI_SLOT_ALL_DEVICES ||
+ PCI_SLOT(dev->devfn) == slot_nr)
dev->slot = slot;
up_read(&pci_bus_sem);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 47c53bbf3f9d8..c7b2b98323bce 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -65,12 +65,23 @@
/* return bus from PCI devid = ((u16)bus_number) << 8) | devfn */
#define PCI_BUS_NUM(x) (((x) >> 8) & 0xff)
+/*
+ * PCI_SLOT_ALL_DEVICES indicates a slot that covers all devices on the bus.
+ * Used for PCIe hotplug where the physical slot is the entire secondary bus,
+ * and, if ARI Forwarding is enabled, functions may appear to be on multiple
+ * devices.
+ */
+#define PCI_SLOT_ALL_DEVICES 0xfe
+
+/* Used to identify a slot as a placeholder */
+#define PCI_SLOT_PLACEHOLDER 0xff
+
/* pci_slot represents a physical slot */
struct pci_slot {
struct pci_bus *bus; /* Bus this slot is on */
struct list_head list; /* Node in list of slots */
struct hotplug_slot *hotplug; /* Hotplug info (move here) */
- unsigned char number; /* PCI_SLOT(pci_dev->devfn) */
+ unsigned char number; /* Device nr, or PCI_SLOT_ALL_DEVICES */
struct kobject kobj;
};
--
2.53.0
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH 5.10.y 3/3] PCI: Allow per function PCI slots to fix slot reset on s390
2026-09-09 14:53 ` [PATCH 5.10.y 1/3] PCI/sysfs: Rely on lengths from scnprintf(), dsm_label_utf16s_to_utf8s() Sasha Levin
2026-09-09 14:53 ` [PATCH 5.10.y 2/3] PCI: Introduce PCI_SLOT_PLACEHOLDER constant for slot_nr placeholder value Sasha Levin
@ 2026-09-09 14:53 ` Sasha Levin
1 sibling, 0 replies; 4+ messages in thread
From: Sasha Levin @ 2026-09-09 14:53 UTC (permalink / raw)
To: stable; +Cc: Farhan Ali, Niklas Schnelle, Bjorn Helgaas, Sasha Levin
From: Farhan Ali <alifm@linux.ibm.com>
[ Upstream commit dcc5bec09e23bbc4f9de055a11fce9937244f2c8 ]
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 pci_create_slot() 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. This creates a problem when resetting
a function through the hotplug driver's slot_reset() interface.
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. Since we can use all 8 bits for
slot 'number' (for ARI devices), change slot 'number' u16 to account for
special values PCI_SLOT_PLACEHOLDER and PCI_SLOT_ALL_DEVICES.
Fixes: 44510d6fa0c0 ("s390/pci: Handling multifunctions")
Suggested-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260805165518.794-3-alifm@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/pci/pci.c | 5 +++--
drivers/pci/slot.c | 29 +++++++++++++++++++++++------
include/linux/pci.h | 7 ++++---
3 files changed, 30 insertions(+), 11 deletions(-)
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 7d887c299e89b..8b69557743ee6 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4871,8 +4871,9 @@ static int pci_reset_hotplug_slot(struct hotplug_slot *hotplug, int probe)
static int pci_dev_reset_slot_function(struct pci_dev *dev, bool probe)
{
- if (dev->multifunction || dev->subordinate || !dev->slot ||
- dev->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET)
+ if (dev->subordinate || !dev->slot ||
+ dev->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET ||
+ (dev->multifunction && !dev->slot->per_func_slot))
return -ENOTTY;
return pci_reset_hotplug_slot(dev->slot->hotplug, probe);
diff --git a/drivers/pci/slot.c b/drivers/pci/slot.c
index 3a125a8417dca..787a49451c2cc 100644
--- a/drivers/pci/slot.c
+++ b/drivers/pci/slot.c
@@ -73,6 +73,23 @@ static ssize_t cur_speed_read_file(struct pci_slot *slot, char *buf)
return bus_speed_read(slot->bus->cur_bus_speed, buf);
}
+static bool pci_dev_matches_slot(struct pci_dev *dev, struct pci_slot *slot)
+{
+ if (slot->per_func_slot)
+ return dev->devfn == slot->number;
+
+ return slot->number == PCI_SLOT_ALL_DEVICES ||
+ PCI_SLOT(dev->devfn) == slot->number;
+}
+
+static bool pci_slot_enabled_per_func(void)
+{
+ if (IS_ENABLED(CONFIG_S390))
+ return true;
+
+ return false;
+}
+
static void pci_slot_release(struct kobject *kobj)
{
struct pci_dev *dev;
@@ -83,8 +100,7 @@ static void pci_slot_release(struct kobject *kobj)
down_read(&pci_bus_sem);
list_for_each_entry(dev, &slot->bus->devices, bus_list)
- if (slot->number == PCI_SLOT_ALL_DEVICES ||
- PCI_SLOT(dev->devfn) == slot->number)
+ if (pci_dev_matches_slot(dev, slot))
dev->slot = NULL;
up_read(&pci_bus_sem);
@@ -176,8 +192,7 @@ void pci_dev_assign_slot(struct pci_dev *dev)
mutex_lock(&pci_slot_mutex);
list_for_each_entry(slot, &dev->bus->slots, list)
- if (slot->number == PCI_SLOT_ALL_DEVICES ||
- PCI_SLOT(dev->devfn) == slot->number)
+ if (pci_dev_matches_slot(dev, slot))
dev->slot = slot;
mutex_unlock(&pci_slot_mutex);
}
@@ -287,6 +302,9 @@ struct pci_slot *pci_create_slot(struct pci_bus *parent, int slot_nr,
slot->bus = pci_bus_get(parent);
slot->number = slot_nr;
+ if (pci_slot_enabled_per_func())
+ slot->per_func_slot = 1;
+
slot->kobj.kset = pci_slots_kset;
slot_name = make_slot_name(name);
@@ -309,8 +327,7 @@ struct pci_slot *pci_create_slot(struct pci_bus *parent, int slot_nr,
down_read(&pci_bus_sem);
list_for_each_entry(dev, &parent->devices, bus_list)
- if (slot_nr == PCI_SLOT_ALL_DEVICES ||
- PCI_SLOT(dev->devfn) == slot_nr)
+ if (pci_dev_matches_slot(dev, slot))
dev->slot = slot;
up_read(&pci_bus_sem);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index c7b2b98323bce..e4ee6473e5f28 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -71,17 +71,18 @@
* and, if ARI Forwarding is enabled, functions may appear to be on multiple
* devices.
*/
-#define PCI_SLOT_ALL_DEVICES 0xfe
+#define PCI_SLOT_ALL_DEVICES 0xfeff
/* Used to identify a slot as a placeholder */
-#define PCI_SLOT_PLACEHOLDER 0xff
+#define PCI_SLOT_PLACEHOLDER 0xffff
/* pci_slot represents a physical slot */
struct pci_slot {
struct pci_bus *bus; /* Bus this slot is on */
struct list_head list; /* Node in list of slots */
struct hotplug_slot *hotplug; /* Hotplug info (move here) */
- unsigned char number; /* Device nr, or PCI_SLOT_ALL_DEVICES */
+ u16 number; /* Device nr, or PCI_SLOT_ALL_DEVICES */
+ unsigned int per_func_slot:1; /* Allow per function slot */
struct kobject kobj;
};
--
2.53.0
^ permalink raw reply related [flat|nested] 4+ messages in thread