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Mon, 16 Mar 2026 19:15:49 +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, kbusch@kernel.org, clg@redhat.com, stable@vger.kernel.org, alifm@linux.ibm.com, schnelle@linux.ibm.com, mjrosato@linux.ibm.com Subject: [PATCH v11 1/9] PCI: Allow per function PCI slots Date: Mon, 16 Mar 2026 12:15:36 -0700 Message-ID: <20260316191544.2279-2-alifm@linux.ibm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260316191544.2279-1-alifm@linux.ibm.com> References: <20260316191544.2279-1-alifm@linux.ibm.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzE2MDE1MyBTYWx0ZWRfX3J/mq3cLYch+ wlq5K5+AvvY+WXIcSJlaEGq3tHtnEzLMkizxd++583xrJ0n5k1Bsb7AgfGNOzG6vEMccqiMAGdz rr2mH4rIBlB0rRYDp51+7fbntALrLJTiT5D1OSfPi/2HIotHu1g+oUzGQd16XszNmafaAuGqQP9 d7W8lH/7RpOjPRQGxou//GcDrpPS42RgfZBQUFqN0HQYUIWCpMSIVdfi4QoYbLL/2F86QweeljB vQofwa6kDsRZdbH+hQ884JSDE+IH+2T68H807JQqplCRUew+03lK4/li/3Yo884WxgEAWAPPF7N OmgxKeqFUXIzbv44B1AJaXT5Vvcu5jdr6c3k18nABxoSVcj2v8Xqm0m9XsSO8mYLBSmjTuOAbzz BYUu0/6TbET09No0+5De8FMmuqv9fZxktCJf6mwr+LWRf1QJN7ORoXkBbMQawcM6P+07jV7LffJ yKwX42gAlVllqwzkeVA== X-Authority-Analysis: v=2.4 cv=GIQF0+NK c=1 sm=1 tr=0 ts=69b856e9 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=dQWU-RC_n072PXZGCE0A:9 a=O8hF6Hzn-FEA:10 X-Proofpoint-ORIG-GUID: F4n-XmIq92N3nWAAO2mt-UA3WmIWVx6G X-Proofpoint-GUID: F4n-XmIq92N3nWAAO2mt-UA3WmIWVx6G X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-16_05,2026-03-16_06,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 priorityscore=1501 bulkscore=0 lowpriorityscore=0 malwarescore=0 phishscore=0 impostorscore=0 suspectscore=0 adultscore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603160153 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. Since we can use all 8 bits for slot 'number' (for ARI devices), change slot 'number' u16 to account for special values -1 and PCI_SLOT_ALL_DEVICES. 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 | 31 ++++++++++++++++++++++++------- include/linux/pci.h | 5 +++-- 3 files changed, 30 insertions(+), 11 deletions(-) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 115e5c11bab3..a93084053537 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -4867,8 +4867,9 @@ static int pci_reset_hotplug_slot(struct hotplug_slot *hotplug, bool 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 e0b7fb43423c..8842fa069392 100644 --- a/drivers/pci/slot.c +++ b/drivers/pci/slot.c @@ -37,7 +37,7 @@ 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 == (u16)-1) return sysfs_emit(buf, "%04x:%02x\n", pci_domain_nr(slot->bus), slot->bus->number); @@ -72,6 +72,23 @@ 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; @@ -82,8 +99,7 @@ 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); @@ -307,8 +325,7 @@ 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 8861eeb4381d..50a84bba3c91 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -78,14 +78,15 @@ * 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 /* 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; }; -- 2.43.0