From 45db33709ccc7330c55fc6751c96468de407f2ac Mon Sep 17 00:00:00 2001 From: Logan Gunthorpe Date: Mon, 30 Jul 2018 10:18:38 -0600 Subject: [PATCH] PCI: Allow specifying devices using a base bus and path of devfns MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When specifying PCI devices on the kernel command line using a bus/device/function address, bus numbers can change when adding or replacing a device, changing motherboard firmware, or applying kernel parameters like "pci=assign-buses". When bus numbers change, it's likely the command line tweak will be applied to the wrong device. Therefore, it is useful to be able to specify devices with a base bus number and the path of devfns needed to get to it, similar to the "device scope" structure in the Intel VT-d spec, Section 8.3.1. Thus, we add an option to specify devices in the following format: [:]:.[/.]* The path can be any segment within the PCI hierarchy of any length and determined through the use of 'lspci -t'. When specified this way, it is less likely that a renumbered bus will result in a valid device specification and the tweak won't be applied to the wrong device. Signed-off-by: Logan Gunthorpe [bhelgaas: use "device" instead of "slot" in documentation since that's the usual language in the PCI specs] Signed-off-by: Bjorn Helgaas Reviewed-by: Stephen Bates Reviewed-by: Alex Williamson Acked-by: Christian König --- .../admin-guide/kernel-parameters.txt | 8 +- drivers/pci/pci.c | 118 ++++++++++++++---- 2 files changed, 103 insertions(+), 23 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index ab36fb34ed01..4fa4c9ff04ae 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3000,7 +3000,7 @@ or a set of devices (). These are specified in one of the following formats: - [:]:. + [:]:.[/.]* pci::[::] Note: the first format specifies a PCI @@ -3009,7 +3009,11 @@ firmware changes, or due to changes caused by other kernel parameters. If the domain is left unspecified, it is - taken to be zero. The second format + taken to be zero. Optionally, a path + to a device through multiple device/function + addresses can be specified after the base + address (this is more robust against + renumbering issues). The second format selects devices using IDs from the configuration space which may match multiple devices in the system. diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 1574b2da25e7..a6c38b15ac33 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -191,6 +191,89 @@ void __iomem *pci_ioremap_wc_bar(struct pci_dev *pdev, int bar) EXPORT_SYMBOL_GPL(pci_ioremap_wc_bar); #endif +/** + * pci_dev_str_match_path - test if a path string matches a device + * @dev: the PCI device to test + * @p: string to match the device against + * @endptr: pointer to the string after the match + * + * Test if a string (typically from a kernel parameter) formatted as a + * path of device/function addresses matches a PCI device. The string must + * be of the form: + * + * [:]:.[/.]* + * + * A path for a device can be obtained using 'lspci -t'. Using a path + * is more robust against bus renumbering than using only a single bus, + * device and function address. + * + * Returns 1 if the string matches the device, 0 if it does not and + * a negative error code if it fails to parse the string. + */ +static int pci_dev_str_match_path(struct pci_dev *dev, const char *path, + const char **endptr) +{ + int ret; + int seg, bus, slot, func; + char *wpath, *p; + char end; + + *endptr = strchrnul(path, ';'); + + wpath = kmemdup_nul(path, *endptr - path, GFP_KERNEL); + if (!wpath) + return -ENOMEM; + + while (1) { + p = strrchr(wpath, '/'); + if (!p) + break; + ret = sscanf(p, "/%x.%x%c", &slot, &func, &end); + if (ret != 2) { + ret = -EINVAL; + goto free_and_exit; + } + + if (dev->devfn != PCI_DEVFN(slot, func)) { + ret = 0; + goto free_and_exit; + } + + /* + * Note: we don't need to get a reference to the upstream + * bridge because we hold a reference to the top level + * device which should hold a reference to the bridge, + * and so on. + */ + dev = pci_upstream_bridge(dev); + if (!dev) { + ret = 0; + goto free_and_exit; + } + + *p = 0; + } + + ret = sscanf(wpath, "%x:%x:%x.%x%c", &seg, &bus, &slot, + &func, &end); + if (ret != 4) { + seg = 0; + ret = sscanf(wpath, "%x:%x.%x%c", &bus, &slot, &func, &end); + if (ret != 3) { + ret = -EINVAL; + goto free_and_exit; + } + } + + ret = (seg == pci_domain_nr(dev->bus) && + bus == dev->bus->number && + dev->devfn == PCI_DEVFN(slot, func)); + +free_and_exit: + kfree(wpath); + return ret; +} + /** * pci_dev_str_match - test if a string matches a device * @dev: the PCI device to test @@ -200,13 +283,16 @@ EXPORT_SYMBOL_GPL(pci_ioremap_wc_bar); * Test if a string (typically from a kernel parameter) matches a specified * PCI device. The string may be of one of the following formats: * - * [:]:. + * [:]:.[/.]* * pci::[::] * * The first format specifies a PCI bus/device/function address which * may change if new hardware is inserted, if motherboard firmware changes, * or due to changes caused in kernel parameters. If the domain is - * left unspecified, it is taken to be 0. + * left unspecified, it is taken to be 0. In order to be robust against + * bus renumbering issues, a path of PCI device/function numbers may be used + * to address the specific device. The path for a device can be determined + * through the use of 'lspci -t'. * * The second format matches devices using IDs in the configuration * space which may match multiple devices in the system. A value of 0 @@ -222,7 +308,7 @@ static int pci_dev_str_match(struct pci_dev *dev, const char *p, const char **endptr) { int ret; - int seg, bus, slot, func, count; + int count; unsigned short vendor, device, subsystem_vendor, subsystem_device; if (strncmp(p, "pci:", 4) == 0) { @@ -248,25 +334,15 @@ static int pci_dev_str_match(struct pci_dev *dev, const char *p, (!subsystem_device || subsystem_device == dev->subsystem_device)) goto found; - } else { - /* PCI Bus, Device, Function IDs are specified */ - ret = sscanf(p, "%x:%x:%x.%x%n", &seg, &bus, &slot, - &func, &count); - if (ret != 4) { - seg = 0; - ret = sscanf(p, "%x:%x.%x%n", &bus, &slot, - &func, &count); - if (ret != 3) - return -EINVAL; - } - - p += count; - - if (seg == pci_domain_nr(dev->bus) && - bus == dev->bus->number && - slot == PCI_SLOT(dev->devfn) && - func == PCI_FUNC(dev->devfn)) + /* + * PCI Bus, Device, Function IDs are specified + * (optionally, may include a path of devfns following it) + */ + ret = pci_dev_str_match_path(dev, p, &p); + if (ret < 0) + return ret; + else if (ret) goto found; }