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Thu, 11 Sep 2025 18:33:10 +0000 (GMT) From: Farhan Ali To: linux-s390@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org Cc: alex.williamson@redhat.com, helgaas@kernel.org, alifm@linux.ibm.com, schnelle@linux.ibm.com, mjrosato@linux.ibm.com Subject: [PATCH v3 03/10] PCI: Allow per function PCI slots Date: Thu, 11 Sep 2025 11:33:00 -0700 Message-ID: <20250911183307.1910-4-alifm@linux.ibm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250911183307.1910-1-alifm@linux.ibm.com> References: <20250911183307.1910-1-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-GUID: HQVFu9CRau-j72qfXJG45PcMar8KGwTU X-Proofpoint-ORIG-GUID: HQVFu9CRau-j72qfXJG45PcMar8KGwTU X-Authority-Analysis: v=2.4 cv=J52q7BnS c=1 sm=1 tr=0 ts=68c315e8 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=yJojWOMRYYMA:10 a=VnNF1IyMAAAA:8 a=K-1LnuYzVcpd1HOvht4A:9 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwOTA2MDAyNSBTYWx0ZWRfX/cuZaSKBQIp5 FzXTCQNI9zNbt2jwzsK+12hL4Y9IqSdhJUklaouWCV/X8iaCqym33DlXa1OxczZiV6yHHHdnwAU 8QSLk+2qAlC4Ul4SnX3QTGbhcWiOo8GEVGJmSxHRXLZ1Oz0Ru9V4spqtGkQ9lo7NpDHVTzBZE8S GsHBFtA3dlnTHQmKjBRaist6zh39btovCX9Tgn5ONyWNkZign5jv35uWlsOYuBPTYYz/+t5Nilf LsANlxNybyUB2ZmUHEy7qBRL6mDEGqCwhthtJma9MrsxZJVB23KpsGIuyb3ydxS71EXXU0hyEG3 DUUoBM1oyc8Gp4F9Ti1pSY1oDqsj4C0oMlrWoqqxLMyfMkSHC4qQ/iJVFMTAHc1OVbkTHagvKEB SkeSR2NV X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1117,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-09-11_03,2025-09-11_02,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 clxscore=1015 suspectscore=0 spamscore=0 phishscore=0 bulkscore=0 adultscore=0 malwarescore=0 priorityscore=1501 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2509060025 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") Suggested-by: Niklas Schnelle Signed-off-by: Farhan Ali --- drivers/pci/hotplug/s390_pci_hpc.c | 10 ++++++++-- drivers/pci/pci.c | 4 +++- drivers/pci/slot.c | 14 +++++++++++--- include/linux/pci.h | 1 + 4 files changed, 23 insertions(+), 6 deletions(-) diff --git a/drivers/pci/hotplug/s390_pci_hpc.c b/drivers/pci/hotplug/s390_= pci_hpc.c index d9996516f49e..8b547de464bf 100644 --- a/drivers/pci/hotplug/s390_pci_hpc.c +++ b/drivers/pci/hotplug/s390_pci_hpc.c @@ -126,14 +126,20 @@ static const struct hotplug_slot_ops s390_hotplug_slo= t_ops =3D { =20 int zpci_init_slot(struct zpci_dev *zdev) { + int ret; char name[SLOT_NAME_SIZE]; struct zpci_bus *zbus =3D zdev->zbus; =20 zdev->hotplug_slot.ops =3D &s390_hotplug_slot_ops; =20 snprintf(name, SLOT_NAME_SIZE, "%08x", zdev->fid); - return pci_hp_register(&zdev->hotplug_slot, zbus->bus, - zdev->devfn, name); + ret =3D pci_hp_register(&zdev->hotplug_slot, zbus->bus, + zdev->devfn, name); + if (ret) + return ret; + + zdev->hotplug_slot.pci_slot->per_func_slot =3D 1; + return 0; } =20 void zpci_exit_slot(struct zpci_dev *zdev) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 3994fa82df68..70296d3b1cfc 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -5061,7 +5061,9 @@ 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 || + if (dev->multifunction && !dev->slot->per_func_slot) + return -ENOTTY; + if (dev->subordinate || !dev->slot || dev->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET) return -ENOTTY; =20 diff --git a/drivers/pci/slot.c b/drivers/pci/slot.c index 50fb3eb595fe..51ee59e14393 100644 --- a/drivers/pci/slot.c +++ b/drivers/pci/slot.c @@ -63,6 +63,14 @@ 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 void pci_slot_release(struct kobject *kobj) { struct pci_dev *dev; @@ -73,7 +81,7 @@ 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 +174,7 @@ 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); } @@ -285,7 +293,7 @@ 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 59876de13860..9265f32d9786 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