When specifying PCI devices on the kernel command line using a
BDF, the bus numbers can change when adding or replacing a device,
changing motherboard firmware, or applying kernel parameters like
pci=assign-buses. When this happens, it is usually undesirable to
apply whatever command line tweak 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:
path:[<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]
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 <logang@xxxxxxxxxxxx>
Reviewed-by: Stephen Bates <sbates@xxxxxxxxxxxx>
Acked-by: Christian König <christian.koenig@xxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 12 ++-
drivers/pci/pci.c | 101 +++++++++++++++++++++++-
2 files changed, 107 insertions(+), 6 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index e58cc671ff92..bc51b316f485 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2989,9 +2989,10 @@
Some options herein operate on a specific device
or a set of devices (<pci_dev>). These are
- specified in one of two formats:
+ specified in one of three formats:
[<domain>:]<bus>:<slot>.<func>
+ path:[<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]
pci:<vendor>:<device>[:<subvendor>:<subdevice>]
Note: the first format specifies a PCI
@@ -2999,9 +3000,12 @@
if new hardware is inserted, if motherboard
firmware changes, or due to changes caused
by other kernel parameters. The second format
- selects devices using IDs from the
- configuration space which may match multiple
- devices in the system.
+ specifies a path from a device through
+ a path of multiple slot/function addresses
+ (this is more robust against renumbering
+ issues). The third format selects devices using
+ IDs from the configuration space which may match
+ multiple devices in the system.
earlydump [X86] dump PCI config space before the kernel
changes anything
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 85fec5e2640b..39f11bd0ee03 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -184,22 +184,111 @@ 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) formated as a
+ * path of slot/function addresses matches a PCI device. The string must
+ * be of the form:
+ *
+ * [<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]
+ *
+ * A path for a device can be obtained using 'lspci -t'. Using a path
+ * is more robust against renumbering of devices than using only
+ * a single bus, slot 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
* @p: string to match the device against
* @endptr: pointer to the string after the match
*
* Test if a string (typically from a kernel parameter) matches a
- * specified. The string may be of one of two forms formats:
+ * specified. The string may be of one of three formats:
*
* [<domain>:]<bus>:<slot>.<func>
+ * path:[<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]
* pci:<vendor>:<device>[:<subvendor>:<subdevice>]
*
* The first format specifies a PCI bus/slot/function address which
* may change if new hardware is inserted, if motherboard firmware changes,
* or due to changes caused in kernel parameters.
*
- * The second format matches devices using IDs in the configuration
+ * The second format specifies a PCI bus/slot/function root address and
+ * a path of slot/function addresses to the specific device from the root.
+ * The path for a device can be determined through the use of 'lspci -t'.
+ * This format is more robust against renumbering issues than the first format.
+
+ * The third format matches devices using IDs in the configuration
* space which may match multiple devices in the system. A value of 0
* for any field will match all devices.
*
@@ -236,7 +325,15 @@ static int pci_dev_str_match(struct pci_dev *dev, const char *p,
(!subsystem_device ||
subsystem_device == dev->subsystem_device))
goto found;
+ } else if (strncmp(p, "path:", 5) == 0) {
+ /* PCI Root Bus and a path of Slot,Function IDs */
+ p += 5;
+ ret = pci_dev_str_match_path(dev, p, &p);
+ if (ret < 0)
+ return ret;
+ else if (ret)
+ goto found;
} else {
/* PCI Bus,Slot,Function ids are specified */
ret = sscanf(p, "%x:%x:%x.%x%n", &seg, &bus, &slot,
--
2.11.0
