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:
[<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>
Reviewed-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 8 +-
drivers/pci/pci.c | 117 ++++++++++++++++++++----
2 files changed, 103 insertions(+), 22 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index e783bcefadac..a69947d9e14e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3000,7 +3000,7 @@
or a set of devices (<pci_dev>). These are
specified in one of the following formats:
- [<domain>:]<bus>:<slot>.<func>
+ [<domain>:]<bus>:<slot>.<func>[/<slot>.<func>]*
pci:<vendor>:<device>[:<subvendor>:<subdevice>]
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 slot/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 cb999b2a9530..3fc823b756e3 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -192,6 +192,89 @@ 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 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 bus renumbering 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
@@ -200,13 +283,16 @@ EXPORT_SYMBOL_GPL(pci_ioremap_wc_bar);
* Test if a string (typically from a kernel parameter) matches a
* specified. The string may be of one of the following formats:
*
- * [<domain>:]<bus>:<slot>.<func>
+ * [<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. 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 slot/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 +334,16 @@ 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,Slot,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;
+ /*
+ * PCI Bus,Slot,Function ids are specified
+ * (optionally, may include a path of devfns following it)
+ */
- if (seg == pci_domain_nr(dev->bus) &&
- bus == dev->bus->number &&
- slot == PCI_SLOT(dev->devfn) &&
- func == PCI_FUNC(dev->devfn))
+ ret = pci_dev_str_match_path(dev, p, &p);
+ if (ret < 0)
+ return ret;
+ else if (ret)
goto found;
}
--
2.11.0
