Introduce a new command line option "pci=pcie_movable_bars" that indicates
support of PCIe hotplug without prior reservation of memory regions by
BIOS/bootloader.
If a new PCIe device has been hot-plugged between two active ones, which
have no (or not big enough) gap between their BARs, allocating new BARs
requires to move BARs of the following working devices:
1) dev 4
|
v
.. | dev 3 | dev 3 | dev 5 | dev 7 |
.. | BAR 0 | BAR 1 | BAR 0 | BAR 0 |
2) dev 4
|
v
.. | dev 3 | dev 3 | --> --> | dev 5 | dev 7 |
.. | BAR 0 | BAR 1 | --> --> | BAR 0 | BAR 0 |
3)
.. | dev 3 | dev 3 | dev 4 | dev 4 | dev 5 | dev 7 |
.. | BAR 0 | BAR 1 | BAR 0 | BAR 1 | BAR 0 | BAR 0 |
Not only BARs, but also bridge windows can be updated during a PCIe rescan,
threatening all memory transactions during this procedure, so the PCI
subsystem will instruct the drivers to pause by calling the reset_prepare()
and reset_done() callbacks.
If a device may be affected by BAR movement, the BAR changes tracking must
be implemented in its driver.
Signed-off-by: Sergey Miroshnichenko <s.miroshnichenko@xxxxxxxxx>
---
.../admin-guide/kernel-parameters.txt | 6 +++
drivers/pci/pci.c | 2 +
drivers/pci/probe.c | 43 +++++++++++++++++++
include/linux/pci.h | 1 +
4 files changed, 52 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 64a3bf54b974..f8132a709061 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3311,6 +3311,12 @@
bridges without forcing it upstream. Note:
this removes isolation between devices and
may put more devices in an IOMMU group.
+ pcie_movable_bars Arrange a space at runtime for BARs of
+ hotplugged PCIe devices - usable if bootloader
+ doesn't reserve memory regions for them. Freeing
+ a space may require moving BARs of active devices
+ to higher addresses, so device drivers will be
+ paused during rescan.
pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
Management.
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 1835f3a7aa8d..5f07a59b5924 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -6105,6 +6105,8 @@ static int __init pci_setup(char *str)
pci_add_flags(PCI_SCAN_ALL_PCIE_DEVS);
} else if (!strncmp(str, "disable_acs_redir=", 18)) {
disable_acs_redir_param = str + 18;
+ } else if (!strncmp(str, "pcie_movable_bars", 17)) {
+ pci_add_flags(PCI_MOVABLE_BARS);
} else {
printk(KERN_ERR "PCI: Unknown option `%s'\n",
str);
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 201f9e5ff55c..bdaafc48dc4c 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -3138,6 +3138,45 @@ unsigned int pci_rescan_bus_bridge_resize(struct pci_dev *bridge)
return max;
}
+/*
+ * Put all devices of the bus and its children to reset
+ */
+static void pci_bus_reset_prepare(struct pci_bus *bus)
+{
+ struct pci_dev *dev;
+
+ list_for_each_entry(dev, &bus->devices, bus_list) {
+ struct pci_bus *child = dev->subordinate;
+
+ if (child) {
+ pci_bus_reset_prepare(child);
+ } else if (dev->driver &&
+ dev->driver->err_handler &&
+ dev->driver->err_handler->reset_prepare) {
+ dev->driver->err_handler->reset_prepare(dev);
+ }
+ }
+}
+
+/*
+ * Complete the reset of all devices for the bus and its children
+ */
+static void pci_bus_reset_done(struct pci_bus *bus)
+{
+ struct pci_dev *dev;
+
+ list_for_each_entry(dev, &bus->devices, bus_list) {
+ struct pci_bus *child = dev->subordinate;
+
+ if (child) {
+ pci_bus_reset_done(child);
+ } else if (dev->driver && dev->driver->err_handler &&
+ dev->driver->err_handler->reset_done) {
+ dev->driver->err_handler->reset_done(dev);
+ }
+ }
+}
+
/**
* pci_rescan_bus - Scan a PCI bus for devices
* @bus: PCI bus to scan
@@ -3151,8 +3190,12 @@ unsigned int pci_rescan_bus(struct pci_bus *bus)
{
unsigned int max;
+ if (pci_has_flag(PCI_MOVABLE_BARS))
+ pci_bus_reset_prepare(bus);
max = pci_scan_child_bus(bus);
pci_assign_unassigned_bus_resources(bus);
+ if (pci_has_flag(PCI_MOVABLE_BARS))
+ pci_bus_reset_done(bus);
pci_bus_add_devices(bus);
return max;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 6925828f9f25..a8cb1a367c34 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -847,6 +847,7 @@ enum {
PCI_ENABLE_PROC_DOMAINS = 0x00000010, /* Enable domains in /proc */
PCI_COMPAT_DOMAIN_0 = 0x00000020, /* ... except domain 0 */
PCI_SCAN_ALL_PCIE_DEVS = 0x00000040, /* Scan all, not just dev 0 */
+ PCI_MOVABLE_BARS = 0x00000080, /* Runtime BAR reassign after hotplug */
};
/* These external functions are only available when PCI support is enabled */
--
2.17.1
