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Mon, 2 Mar 2026 20:33:26 +0000 (GMT) From: Farhan Ali To: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org Cc: helgaas@kernel.org, lukas@wunner.de, alex@shazbot.org, clg@redhat.com, stable@vger.kernel.org, kbusch@kernel.org, alifm@linux.ibm.com, schnelle@linux.ibm.com, mjrosato@linux.ibm.com Subject: [PATCH v10 1/9] PCI: Allow per function PCI slots Date: Mon, 2 Mar 2026 12:33:16 -0800 Message-ID: <20260302203325.3826-2-alifm@linux.ibm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260302203325.3826-1-alifm@linux.ibm.com> References: <20260302203325.3826-1-alifm@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzAyMDE1NSBTYWx0ZWRfXxmlYuzwCMCqh Jrq+aTe2EO722D8YaT5MxddWrqsnqVJrrHrpWA4L+/L8fzA36kFrrrDNJvvvkFNflkOuyMoJZEI dcAUFH7y3COcI8VL2QGzofXXuL5WV6oMQyaJ6wqEWntIO/7sf5Ym2X8R0U7W7s+fdVfmAMTGRIk EG1pPEB5Da8O4cWZLtev9H/l+RYqpNGCCmt5nS/5d2ohp/8+3HlCSFkGJx0ni6119LKBFmZIaI4 UIU6/zUzm+OQa/LYvhN3NfDj5sT+up0KcRepShUL79ya89QpmIl4sF20NUlU0teq5kAduvRzWct HxqOWk6GjABIfTE9OnEk6kNAhqdNltp5TJG6fdyklRz//Tm4me7aY0X00kaYFCrolukxZUZL/0v R9aPqDjPk4tFC6GvyelR0PTB9DzV+ARUSkUEC1cnjuqbbfXjaNHPDV/ZWdt1jHjKFXDVE74//wc vzpIMOi5mdAOrXNsijg== X-Proofpoint-ORIG-GUID: dN632UuxB_yMlsoL-yG6WIh66J-wq8HR X-Proofpoint-GUID: dN632UuxB_yMlsoL-yG6WIh66J-wq8HR X-Authority-Analysis: v=2.4 cv=AobjHe9P c=1 sm=1 tr=0 ts=69a5f41a cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=pvJWqFYHg2AjC0HbIRAA:9 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-02_05,2026-03-02_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 lowpriorityscore=0 bulkscore=0 impostorscore=0 malwarescore=0 spamscore=0 clxscore=1015 suspectscore=0 adultscore=0 priorityscore=1501 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2602130000 definitions=main-2603020155 Content-Type: text/plain; charset="utf-8" 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 Reviewed-by: Niklas Schnelle Signed-off-by: Farhan Ali --- drivers/pci/pci.c | 5 +++-- drivers/pci/slot.c | 27 +++++++++++++++++++++++---- include/linux/pci.h | 3 ++- 3 files changed, 28 insertions(+), 7 deletions(-) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 8479c2e1f74f..b2781577ddbe 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -4868,8 +4868,9 @@ static int pci_reset_hotplug_slot(struct hotplug_slot= *hotplug, bool probe) =20 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; =20 return pci_reset_hotplug_slot(dev->slot->hotplug, probe); diff --git a/drivers/pci/slot.c b/drivers/pci/slot.c index 787311614e5b..125e6c2d4786 100644 --- a/drivers/pci/slot.c +++ b/drivers/pci/slot.c @@ -37,7 +37,7 @@ static const struct sysfs_ops pci_slot_sysfs_ops =3D { =20 static ssize_t address_read_file(struct pci_slot *slot, char *buf) { - if (slot->number =3D=3D 0xff) + if (slot->number =3D=3D -1) return sysfs_emit(buf, "%04x:%02x\n", pci_domain_nr(slot->bus), slot->bus->number); @@ -63,6 +63,22 @@ static ssize_t cur_speed_read_file(struct pci_slot *slot= , char *buf) return bus_speed_read(slot->bus->cur_bus_speed, buf); } =20 +static bool pci_dev_matches_slot(struct pci_dev *dev, struct pci_slot *slo= t) +{ + if (slot->per_func_slot) + return dev->devfn =3D=3D slot->number; + + return PCI_SLOT(dev->devfn) =3D=3D 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; @@ -73,7 +89,7 @@ static void pci_slot_release(struct kobject *kobj) =20 down_read(&pci_bus_sem); list_for_each_entry(dev, &slot->bus->devices, bus_list) - if (PCI_SLOT(dev->devfn) =3D=3D slot->number) + if (pci_dev_matches_slot(dev, slot)) dev->slot =3D NULL; up_read(&pci_bus_sem); =20 @@ -166,7 +182,7 @@ void pci_dev_assign_slot(struct pci_dev *dev) =20 mutex_lock(&pci_slot_mutex); list_for_each_entry(slot, &dev->bus->slots, list) - if (PCI_SLOT(dev->devfn) =3D=3D slot->number) + if (pci_dev_matches_slot(dev, slot)) dev->slot =3D slot; mutex_unlock(&pci_slot_mutex); } @@ -265,6 +281,9 @@ struct pci_slot *pci_create_slot(struct pci_bus *parent= , int slot_nr, slot->bus =3D pci_bus_get(parent); slot->number =3D slot_nr; =20 + if (pci_slot_enabled_per_func()) + slot->per_func_slot =3D 1; + slot->kobj.kset =3D pci_slots_kset; =20 slot_name =3D make_slot_name(name); @@ -285,7 +304,7 @@ struct pci_slot *pci_create_slot(struct pci_bus *parent= , int slot_nr, =20 down_read(&pci_bus_sem); list_for_each_entry(dev, &parent->devices, bus_list) - if (PCI_SLOT(dev->devfn) =3D=3D slot_nr) + if (pci_dev_matches_slot(dev, slot)) dev->slot =3D slot; up_read(&pci_bus_sem); =20 diff --git a/include/linux/pci.h b/include/linux/pci.h index 1c270f1d5123..63febdc50b21 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -77,7 +77,8 @@ 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) */ + u16 number; /* PCI_SLOT(pci_dev->devfn) */ + unsigned int per_func_slot:1; /* Allow per function slot */ struct kobject kobj; }; =20 --=20 2.43.0