[PATCH v3] PCI: add kernel parameter to override devid<->driver mapping.

Discussion:

Marcel Apfelbaum

2014-10-07 14:48:32 UTC

Scanning a lot of devices during boot requires a lot of time.
On other scenarios there is a need to bind a driver to a specific slot.

Binding devices to pci-stub driver does not work,
as it will not differentiate between devices of the
same type. Using some start scripts is error prone.

The solution leverages driver_override functionality introduced by

commit: 782a985d7af26db39e86070d28f987cad21313c0
Author: Alex Williamson <***@redhat.com>
Date: Tue May 20 08:53:21 2014 -0600

PCI: Introduce new device binding path using pci_dev.driver_override

In order to bind PCI slots to specific drivers use:
pci=driver[xxxx:xx:xx.x]=foo,driver[xxxx:xx:xx.x]=bar,...

Signed-off-by: Marcel Apfelbaum <***@redhat.com>
---
v2 -> v3:
- Corrected subject line
v1 -> v2:
- Addressed Michael S. Tsirkin comments
- Removed 32 slots limitation
- Better handling of memory allocation failures
(preferred BUG_ON over error messages)
- Addressed Alex Williamson's comments:
- Modified commit message to show parameter usage more clear.
- I preferred to re-use parse_args instead of manually using
strstr in order to better comply with command line parsing
rules.
- I didn't use any locking when parsing the command line args
(see parse_done usage) assuming that first call will be
early in system boot and no race can occur. Please correct
me if I am wrong.

Notes:
- I have further ideas on top of this patch based on your reviews.
I thought of:
- Use wildcards to specify entire buses/devices, something like:
driver[0001:02:*.*]=pci-stub
- Use comma to separate several devices:
driver[0001:02:03.4,0001:02:04.0,...]=pci-stub
- Make domain optional:
driver[00:03.0]=pci-stub

Comments will be appreciated,
Thanks,
Marcel
Documentation/kernel-parameters.txt | 4 ++
drivers/pci/bus.c | 86 +++++++++++++++++++++++++++++++++++++
drivers/pci/pci.c | 2 +
3 files changed, 92 insertions(+)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 5ae8608..c1cbb4c 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2631,6 +2631,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
pcie_scan_all Scan all possible PCIe devices. Otherwise we
only look for one device below a PCIe downstream
port.
+ driver Provide an override to the devid<->driver mapping
+ for a specific slot.
+ Bind PCI slot 0001:02:03.4 to pci-stub by:
+ driver[0001:02:03.4]=pci-stub

pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
Management.
diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index 73aef51..d2c0721 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -230,6 +230,91 @@ EXPORT_SYMBOL(pci_bus_alloc_resource);

void __weak pcibios_resource_survey_bus(struct pci_bus *bus) { }

+#define DRIVER_OVERRIDE_NAME_LENGTH 64
+
+struct driver_override_entry {
+ unsigned int domain;
+ unsigned char bus;
+ unsigned int devfn;
+ char driver_name[DRIVER_OVERRIDE_NAME_LENGTH];
+ struct list_head list;
+};
+
+static LIST_HEAD(driver_override_entries);
+
+static int pci_device_parse_driver_override(char *param, char *val,
+ const char *unused)
+{
+ unsigned int domain, bus, dev, fn;
+ char driver_name[DRIVER_OVERRIDE_NAME_LENGTH];
+ char format[] = "[%4x:%2x:%2x.%2x]=%%%ds";
+ struct driver_override_entry *entry;
+ int ret;
+
+ while (val) {
+ char *k = strchr(val, ',');
+
+ if (k)
+ *k++ = 0;
+
+ if (strncmp(val, "driver", 6)) {
+ val = k;
+ continue;
+ }
+
+ sprintf(format + 18, "%%%ds", DRIVER_OVERRIDE_NAME_LENGTH);
+ ret = sscanf(val + 6, format, &domain, &bus, &dev, &fn,
+ driver_name);
+ if (ret != 5) {
+ pr_err("PCI: Invalid command line: %s\n", val);
+ val = k;
+ continue;
+ }
+
+ entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+ BUG_ON(!entry);
+
+ INIT_LIST_HEAD(&entry->list);
+ entry->domain = domain;
+ entry->bus = bus && 0xff;
+ entry->devfn = ((dev & 0x1f) << 3) | (fn & 0x7);
+ memcpy(entry->driver_name, driver_name, sizeof(driver_name));
+
+ list_add_tail(&entry->list, &driver_override_entries);
+ val = k;
+ }
+
+ return 0;
+}
+
+static void pci_device_setup_driver_override(struct pci_dev *dev)
+{
+ static int parse_done;
+ struct driver_override_entry *entry;
+
+ if (!parse_done) {
+ char *cmdline = kstrdup(saved_command_line, GFP_KERNEL);
+
+ BUG_ON(!cmdline);
+
+ parse_args("pci", cmdline, NULL,
+ 0, 0, 0, &pci_device_parse_driver_override);
+ kfree(cmdline);
+ parse_done = 1;
+ }
+
+ list_for_each_entry(entry, &driver_override_entries, list) {
+ if (pci_domain_nr(dev->bus) != entry->domain ||
+ dev->bus->number != entry->bus ||
+ dev->devfn != entry->devfn)
+ continue;
+
+ dev->driver_override = kstrdup(entry->driver_name, GFP_KERNEL);
+ BUG_ON(!dev->driver_override);
+ break;
+ }
+}
+
/**
* pci_bus_add_device - start driver for a single device
* @dev: device to add
@@ -245,6 +330,7 @@ void pci_bus_add_device(struct pci_dev *dev)
* are not assigned yet for some devices.
*/
pci_fixup_device(pci_fixup_final, dev);
+ pci_device_setup_driver_override(dev);
pci_create_sysfs_dev_files(dev);
pci_proc_attach_device(dev);

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b7678be..6bd7844 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4468,6 +4468,8 @@ static int __init pci_setup(char *str)
pcie_bus_config = PCIE_BUS_PEER2PEER;
} else if (!strncmp(str, "pcie_scan_all", 13)) {
pci_add_flags(PCI_SCAN_ALL_PCIE_DEVS);
+ } else if (!strncmp(str, "driver", 6)) {
+ /* lazy evaluation by the pci subsystem */
} else {
printk(KERN_ERR "PCI: Unknown option `%s'\n",
str);

--
1.8.3.1

Michael S. Tsirkin

2014-10-07 15:02:09 UTC

Permalink

Post by Marcel Apfelbaum
Scanning a lot of devices during boot requires a lot of time.
On other scenarios there is a need to bind a driver to a specific slot.
Binding devices to pci-stub driver does not work,
as it will not differentiate between devices of the
same type. Using some start scripts is error prone.
The solution leverages driver_override functionality introduced by
commit: 782a985d7af26db39e86070d28f987cad21313c0
Date: Tue May 20 08:53:21 2014 -0600
PCI: Introduce new device binding path using pci_dev.driver_override
pci=driver[xxxx:xx:xx.x]=foo,driver[xxxx:xx:xx.x]=bar,...
---
- Corrected subject line
- Addressed Michael S. Tsirkin comments
- Removed 32 slots limitation
- Better handling of memory allocation failures
(preferred BUG_ON over error messages)
- Modified commit message to show parameter usage more clear.
- I preferred to re-use parse_args instead of manually using
strstr in order to better comply with command line parsing
rules.
- I didn't use any locking when parsing the command line args
(see parse_done usage) assuming that first call will be
early in system boot and no race can occur. Please correct
me if I am wrong.
- I have further ideas on top of this patch based on your reviews.
driver[0001:02:*.*]=pci-stub
driver[0001:02:03.4,0001:02:04.0,...]=pci-stub
driver[00:03.0]=pci-stub
Comments will be appreciated,
Thanks,
Marcel
Documentation/kernel-parameters.txt | 4 ++
drivers/pci/bus.c | 86 +++++++++++++++++++++++++++++++++++++
drivers/pci/pci.c | 2 +
3 files changed, 92 insertions(+)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 5ae8608..c1cbb4c 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2631,6 +2631,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
pcie_scan_all Scan all possible PCIe devices. Otherwise we
only look for one device below a PCIe downstream
port.
+ driver Provide an override to the devid<->driver mapping
+ for a specific slot.
+ driver[0001:02:03.4]=pci-stub
pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
Management.
diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index 73aef51..d2c0721 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -230,6 +230,91 @@ EXPORT_SYMBOL(pci_bus_alloc_resource);
void __weak pcibios_resource_survey_bus(struct pci_bus *bus) { }
+#define DRIVER_OVERRIDE_NAME_LENGTH 64

Do we know all drivers have shorter names?

Post by Marcel Apfelbaum
+
+struct driver_override_entry {
+ unsigned int domain;
+ unsigned char bus;
+ unsigned int devfn;
+ char driver_name[DRIVER_OVERRIDE_NAME_LENGTH];
+ struct list_head list;
+};
+
+static LIST_HEAD(driver_override_entries);
+
+static int pci_device_parse_driver_override(char *param, char *val,
+ const char *unused)
+{
+ unsigned int domain, bus, dev, fn;
+ char driver_name[DRIVER_OVERRIDE_NAME_LENGTH];
+ char format[] = "[%4x:%2x:%2x.%2x]=%%%ds";
+ struct driver_override_entry *entry;
+ int ret;
+
+ while (val) {
+ char *k = strchr(val, ',');
+
+ if (k)
+ *k++ = 0;
+
+ if (strncmp(val, "driver", 6)) {
+ val = k;
+ continue;
+ }
+
+ sprintf(format + 18, "%%%ds", DRIVER_OVERRIDE_NAME_LENGTH);
+ ret = sscanf(val + 6, format, &domain, &bus, &dev, &fn,
+ driver_name);
+ if (ret != 5) {
+ pr_err("PCI: Invalid command line: %s\n", val);
+ val = k;
+ continue;
+ }
+
+ entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+ BUG_ON(!entry);
+
+ INIT_LIST_HEAD(&entry->list);
+ entry->domain = domain;
+ entry->bus = bus && 0xff;
+ entry->devfn = ((dev & 0x1f) << 3) | (fn & 0x7);
+ memcpy(entry->driver_name, driver_name, sizeof(driver_name));
+
+ list_add_tail(&entry->list, &driver_override_entries);
+ val = k;
+ }
+
+ return 0;
+}
+
+static void pci_device_setup_driver_override(struct pci_dev *dev)
+{
+ static int parse_done;
+ struct driver_override_entry *entry;
+
+ if (!parse_done) {
+ char *cmdline = kstrdup(saved_command_line, GFP_KERNEL);
+
+ BUG_ON(!cmdline);
+
+ parse_args("pci", cmdline, NULL,
+ 0, 0, 0, &pci_device_parse_driver_override);
+ kfree(cmdline);
+ parse_done = 1;
+ }
+
+ list_for_each_entry(entry, &driver_override_entries, list) {
+ if (pci_domain_nr(dev->bus) != entry->domain ||
+ dev->bus->number != entry->bus ||
+ dev->devfn != entry->devfn)
+ continue;
+
+ dev->driver_override = kstrdup(entry->driver_name, GFP_KERNEL);
+ BUG_ON(!dev->driver_override);
+ break;
+ }
+}
+
/**
* pci_bus_add_device - start driver for a single device
@@ -245,6 +330,7 @@ void pci_bus_add_device(struct pci_dev *dev)
* are not assigned yet for some devices.
*/
pci_fixup_device(pci_fixup_final, dev);
+ pci_device_setup_driver_override(dev);
pci_create_sysfs_dev_files(dev);
pci_proc_attach_device(dev);
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b7678be..6bd7844 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4468,6 +4468,8 @@ static int __init pci_setup(char *str)
pcie_bus_config = PCIE_BUS_PEER2PEER;
} else if (!strncmp(str, "pcie_scan_all", 13)) {
pci_add_flags(PCI_SCAN_ALL_PCIE_DEVS);
+ } else if (!strncmp(str, "driver", 6)) {
+ /* lazy evaluation by the pci subsystem */
} else {
printk(KERN_ERR "PCI: Unknown option `%s'\n",
str);
--
1.8.3.1

Marcel Apfelbaum

2014-10-07 15:13:51 UTC

Permalink

Post by Michael S. Tsirkin

Do we know all drivers have shorter names?

Hi Michael,

I saw this assumption in at least one place (sadly I don't remember where)
and I chose to follow it. It seems a reasonable one in my opinion.

Thanks,
Marcel

Post by Michael S. Tsirkin