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Wed, 22 Oct 2025 21:24:14 +0000 (GMT) From: Farhan Ali To: linux-s390@vger.kernel.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Cc: helgaas@kernel.org, alifm@linux.ibm.com, schnelle@linux.ibm.com, mjrosato@linux.ibm.com, bblock@linux.ibm.com, agordeev@linux.ibm.com, gor@linux.ibm.com, hca@linux.ibm.com, stable@vger.kernel.org Subject: [PATCH v2 1/2] PCI: Allow per function PCI slots Date: Wed, 22 Oct 2025 14:24:10 -0700 Message-ID: <20251022212411.1989-2-alifm@linux.ibm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251022212411.1989-1-alifm@linux.ibm.com> References: <20251022212411.1989-1-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-ORIG-GUID: 3XoZJ5bXwitHIvOaVSFFPnqDjneaklcB X-Proofpoint-GUID: 3XoZJ5bXwitHIvOaVSFFPnqDjneaklcB X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMDE4MDAyMiBTYWx0ZWRfXz+p/6deDM0Bb iaCU5tsqyywTot8d1a9Ayti38EqU4aur3XSsVtaG6i6B6GKXEgiCwdEjVWJi9TWuJigqU/35Z/a 8qT4sNii56nLTkFKmWYycqZtx8wb2LtChCM96vX5+GyUuOIG7b604Hotrz7jMa0+zvBZvQbUYrz J/B4tRZJrIrFwxhg6DFXdIjT4Ukam8GlyVPKgsAzWcpQ93pyxM+rizkq1C+LcnYscsXxIy1XE4F Kn38UUs8Tn0CUmqlwN0/sSC9aGyqUt1zG2lzsbL54WSJ5wFnU1b3dDbl3tIVAuhGH9JZvki1cA/ WgGHhnc1sifB7eeQjB6fQ7MSZgBIivczogBs6RyU6DJNNSX3Sz+BpL9F3FCCDFSo41IVx/6VdVv QIv4EFSBzf99VFI37hJ5fiBrPF0JSw== X-Authority-Analysis: v=2.4 cv=IJYPywvG c=1 sm=1 tr=0 ts=68f94b82 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=x6icFKpwvdMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=Oaqo05sdQjFGKWlA34QA:9 a=cPQSjfK2_nFv0Q5t_7PE:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-10-22_08,2025-10-22_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 lowpriorityscore=0 clxscore=1015 suspectscore=0 spamscore=0 bulkscore=0 adultscore=0 impostorscore=0 malwarescore=0 priorityscore=1501 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510020000 definitions=main-2510180022 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 Signed-off-by: Farhan Ali Reviewed-by: Niklas Schnelle --- drivers/pci/pci.c | 5 +++-- drivers/pci/slot.c | 25 ++++++++++++++++++++++--- include/linux/pci.h | 1 + 3 files changed, 26 insertions(+), 5 deletions(-) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index b14dd064006c..36ee38e0d817 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -4980,8 +4980,9 @@ 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 50fb3eb595fe..ed10fa3ae727 100644 --- a/drivers/pci/slot.c +++ b/drivers/pci/slot.c @@ -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 d1fdf81fbe1e..6ad194597ab5 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -78,6 +78,7 @@ struct pci_slot { 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 int per_func_slot:1; /* Allow per function slot */ struct kobject kobj; }; =20 --=20 2.43.0