From 2fa046449a82a7d0f6d9721dd83e348816038444 Mon Sep 17 00:00:00 2001 From: Keith Busch Date: Fri, 25 Oct 2024 15:27:54 -0700 Subject: [PATCH 1/2] PCI: Add 'reset_subordinate' to reset hierarchy below bridge The "bus" and "cxl_bus" reset methods reset a device by asserting Secondary Bus Reset on the bridge leading to the device. These only work if the device is the only device below the bridge. Add a sysfs 'reset_subordinate' attribute on bridges that can assert Secondary Bus Reset regardless of how many devices are below the bridge. This resets all the devices below a bridge in a single command, including the locking and config space save/restore that reset methods normally do. This may be the only way to reset devices that don't support other reset methods (ACPI, FLR, PM reset, etc). Link: https://lore.kernel.org/r/20241025222755.3756162-1-kbusch@meta.com Signed-off-by: Keith Busch [bhelgaas: commit log, add capable(CAP_SYS_ADMIN) check] Signed-off-by: Bjorn Helgaas Reviewed-by: Alex Williamson Reviewed-by: Amey Narkhede --- Documentation/ABI/testing/sysfs-bus-pci | 11 +++++++++++ drivers/pci/pci-sysfs.c | 26 +++++++++++++++++++++++++ drivers/pci/pci.c | 2 +- drivers/pci/pci.h | 1 + 4 files changed, 39 insertions(+), 1 deletion(-) diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci index 7f63c7e97773..5da6a14dc326 100644 --- a/Documentation/ABI/testing/sysfs-bus-pci +++ b/Documentation/ABI/testing/sysfs-bus-pci @@ -163,6 +163,17 @@ Description: will be present in sysfs. Writing 1 to this file will perform reset. +What: /sys/bus/pci/devices/.../reset_subordinate +Date: October 2024 +Contact: linux-pci@vger.kernel.org +Description: + This is visible only for bridge devices. If you want to reset + all devices attached through the subordinate bus of a specific + bridge device, writing 1 to this will try to do it. This will + affect all devices attached to the system through this bridge + similiar to writing 1 to their individual "reset" file, so use + with caution. + What: /sys/bus/pci/devices/.../vpd Date: February 2008 Contact: Ben Hutchings diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c index 5d0f4db1cab7..3e5a117f5b5d 100644 --- a/drivers/pci/pci-sysfs.c +++ b/drivers/pci/pci-sysfs.c @@ -521,6 +521,31 @@ static ssize_t bus_rescan_store(struct device *dev, static struct device_attribute dev_attr_bus_rescan = __ATTR(rescan, 0200, NULL, bus_rescan_store); +static ssize_t reset_subordinate_store(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t count) +{ + struct pci_dev *pdev = to_pci_dev(dev); + struct pci_bus *bus = pdev->subordinate; + unsigned long val; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + if (kstrtoul(buf, 0, &val) < 0) + return -EINVAL; + + if (val) { + int ret = __pci_reset_bus(bus); + + if (ret) + return ret; + } + + return count; +} +static DEVICE_ATTR_WO(reset_subordinate); + #if defined(CONFIG_PM) && defined(CONFIG_ACPI) static ssize_t d3cold_allowed_store(struct device *dev, struct device_attribute *attr, @@ -625,6 +650,7 @@ static struct attribute *pci_dev_attrs[] = { static struct attribute *pci_bridge_attrs[] = { &dev_attr_subordinate_bus_number.attr, &dev_attr_secondary_bus_number.attr, + &dev_attr_reset_subordinate.attr, NULL, }; diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 7d85c04fbba2..338dfcd983f1 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -5880,7 +5880,7 @@ EXPORT_SYMBOL_GPL(pci_probe_reset_bus); * * Same as above except return -EAGAIN if the bus cannot be locked */ -static int __pci_reset_bus(struct pci_bus *bus) +int __pci_reset_bus(struct pci_bus *bus) { int rc; diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h index 14d00ce45bfa..1cdc2c9547a7 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -104,6 +104,7 @@ bool pci_reset_supported(struct pci_dev *dev); void pci_init_reset_methods(struct pci_dev *dev); int pci_bridge_secondary_bus_reset(struct pci_dev *dev); int pci_bus_error_reset(struct pci_dev *dev); +int __pci_reset_bus(struct pci_bus *bus); struct pci_cap_saved_data { u16 cap_nr; From a3151e6daaec171b7d46ac79170ec420ad874cae Mon Sep 17 00:00:00 2001 From: Keith Busch Date: Fri, 25 Oct 2024 15:27:55 -0700 Subject: [PATCH 2/2] PCI: Warn if a running device is unaware of reset If a reset is issued to a running device with a driver that didn't register the notification callbacks, the driver may be unaware of this event and have an inconsistent view of the device's state. Log a warning of this event because there's nothing else indicating the event occured, which could be confusing when debugging such situations. Link: https://lore.kernel.org/r/20241025222755.3756162-2-kbusch@meta.com Signed-off-by: Keith Busch Signed-off-by: Bjorn Helgaas Reviewed-by: Amey Narkhede Reviewed-by: Alex Williamson --- drivers/pci/pci.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 338dfcd983f1..bbf12d499826 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -5158,6 +5158,8 @@ static void pci_dev_save_and_disable(struct pci_dev *dev) */ if (err_handler && err_handler->reset_prepare) err_handler->reset_prepare(dev); + else if (dev->driver) + pci_warn(dev, "resetting"); /* * Wake-up device prior to save. PM registers default to D0 after @@ -5191,6 +5193,8 @@ static void pci_dev_restore(struct pci_dev *dev) */ if (err_handler && err_handler->reset_done) err_handler->reset_done(dev); + else if (dev->driver) + pci_warn(dev, "reset done"); } /* dev->reset_methods[] is a 0-terminated list of indices into this array */