Currently PCI hotplug works on top of resources which are usually reserved:
by BIOS, bootloader, firmware, or by the kernel (pci=hpmemsize=XM). These
resources are gaps in the address space where BARs of new devices may fit,
and extra bus number per port, so bridges can be hot-added. This series aim
the BARs problem: it shows the kernel how to redistribute them on the run,
so the hotplug becomes predictable and cross-platform. A follow-up patchset
will propose a solution for bus numbers. And another one -- for the powerpc
arch-specific problems.
To arrange a space for BARs of new hot-added devices, the kernel can pause
the drivers of working PCI devices and reshuffle the assigned BARs. When a
driver is un-paused by the kernel, it should ioremap() the new addresses of
its BARs.
Drivers indicate their support of the feature by implementing the new hooks
.bar_fixed(), .rescan_prepare(), .rescan_done() in the struct pci_driver.
If a driver doesn't yet support the feature, BARs of its devices are seen
as immovable and handled in the same way as resources with the PCI_FIXED
flag: they are guaranteed to remain untouched.
This approached was discussed during LPC 2020 [1].
The feature is usable not only for hotplug, but also for booting with a
complete set of BARs assigned, and for Resizable BARs.
Tested on a number of x86_64 machines without any special kernel command
line arguments (some of them -- with older v8 revision of this patchset):
- PC: i7-5930K + ASUS X99-A;
- PC: i5-8500 + ASUS Z370-F;
- PC: AMD Ryzen 7 3700X + ASRock X570 + AMD 5700 XT (Resizable BARs);
- Supermicro Super Server/H11SSL-i: AMD EPYC 7251;
- HP ProLiant DL380 G5: Xeon X5460;
- Dell Inspiron N5010: i5 M 480;
- Dell Precision M6600: i7-2920XM.
Also tested on a Power8 (Vesnin) and Power9 (Nicole) ppc64le machines, but
with extra patchset, which is to be sent upstream a bit later.
The set contains:
01-02: Independent bugfixes, both are not related directly to the movable
BARs feature, but without them the rest of this series will not
work as expected;
03-14: Implement the essentials of the feature;
15-21: Performance improvements for movable BARs and pciehp;
22: Enable the feature by default;
23-24: Add movable BARs support to nvme and portdrv;
25-26: Debugging helpers.
This patchset is a part of our work on adding support for hot-adding
chains of chassis full of other bridges, NVME drives, SAS HBAs, GPUs, etc.
without special requirements such as Hot-Plug Controller, reservation of
bus numbers or memory regions by firmware, etc.
[1] https://linuxplumbersconf.org/event/7/contributions/847/attachments/584/1035/lpc2020_sergmir.pdf
LPC 2020: VFIO/IOMMU/PCI MC: PCI hotplug: movable BARs and bus numbers
Changes since v8:
- Fixed support of Resizable BARs, with amdgpu (no changes in the driver);
- Added a new hook .bar_fixed(), so part of device's BARs can be movable,
and this new call makes the API a bit cleaner in usage;
- Memory reservation (via pci=hpmemsize, etc) now works as well;
- Fix for a race condition (patch 01) has been simplified;
- Simplified: the .realloc_range field is not needed anymore;
- Added some debug messages;
- Compilation warnings, NULL dereference fixed.
Changes since v7:
- Added some documentation;
- Replaced every occurrence of the word "immovable" with "fixed";
- Don't touch PNP, ACPI resources anymore;
- Replaced double rescan with triple rescan:
* first try every BAR;
* if that failed, retry without BARs which weren't assigned before;
* if that failed, retry without BARs of hotplugged devices;
- Reassign BARs during boot only if BIOS assigned not all requested BARs;
- Fixed up PCIBIOS_MIN_MEM instead of ignoring it;
- Now the feature auto-disables in presence of a transparent bridge;
- Improved support of runtime PM;
- Fixed issues with incorrectly released bridge windows;
- Fixed calculating bridge window size.
Changes since v6:
- Added a fix for hotplug on AMD Epyc + Supermicro H11SSL-i by ignoring
PCIBIOS_MIN_MEM;
- Fixed a workaround which marks VGA BARs as immovables;
- Fixed misleading "can't claim BAR ... no compatible bridge window" error
messages;
- Refactored the code, reduced the amount of patches;
- Exclude PowerPC-specific arch patches, they will be sent separately;
- Disabled for PowerNV by default - waiting for the PCIPOCALYPSE patchset.
- Fixed reports from the kbuild test robot.
Changes since v5:
- Simplified the disable flag, now it is "pci=no_movable_buses";
- More deliberate marking the BARs as immovable;
- Mark as immovable BARs which are used by unbound drivers;
- Ignoring BAR assignment by non-kernel program components, so the kernel
is able now to distribute BARs in optimal and predictable way;
- Move here PowerNV-specific patches from the older "powerpc/powernv/pci:
Make hotplug self-sufficient, independent of FW and DT" series;
- Fix EEH cache rebuilding and PE allocation for PowerNV during rescan.
Changes since v4:
- Feature is enabled by default (turned on by one of the latest patches);
- Add pci_dev_movable_bars_supported(dev) instead of marking the immovable
BARs with the IORESOURCE_PCI_FIXED flag;
- Set up PCIe bridges during rescan via sysfs, so MPS settings are now
configured not only during system boot or pcihp events;
- Allow movement of switch's BARs if claimed by portdrv;
- Update EEH address caches after rescan for powerpc;
- Don't disable completely hot-added devices which can't have BARs being
fit - just disable their BARs, so they are still visible in lspci etc;
- Clearer names: fixed_range_hard -> immovable_range, fixed_range_soft ->
realloc_range;
- Drop the patch for pci_restore_config_space() - fixed by properly using
the runtime PM.
Changes since v3:
- Rebased to the upstream, so the patches apply cleanly again.
Changes since v2:
- Fixed double-assignment of bridge windows;
- Fixed assignment of fixed prefetched resources;
- Fixed releasing of fixed resources;
- Fixed a debug message;
- Removed auto-enabling the movable BARs for x86 - let's rely on the
"pcie_movable_bars=force" option for now;
- Reordered the patches - bugfixes first.
Changes since v1:
- Add a "pcie_movable_bars={ off | force }" command line argument;
- Handle the IORESOURCE_PCI_FIXED flag properly;
- Don't move BARs of devices which don't support the feature;
- Guarantee that new hotplugged devices will not steal memory from working
devices by ignoring the failing new devices with the new PCI_DEV_IGNORE
flag;
- Add rescan_prepare()+rescan_done() to the struct pci_driver instead of
using the reset_prepare()+reset_done() from struct pci_error_handlers;
- Add a bugfix of a race condition;
- Fixed hotplug in a non-pre-enabled (by BIOS/firmware) bridge;
- Fix the compatibility of the feature with pm_runtime and D3-state;
- Hotplug events from pciehp also can move BARs;
- Add support of the feature to the NVME driver.
Sergei Miroshnichenko (26):
PCI: Fix race condition in pci_enable/disable_device()
PCI: Ensure a bridge has I/O and MEM access for hot-added devices
PCI: hotplug: Initial support of the movable BARs feature
PCI: Add version of release_child_resources() aware of fixed BARs
PCI: hotplug: Fix reassigning the released BARs
PCI: hotplug: Recalculate every bridge window during rescan
PCI: hotplug: Don't allow hot-added devices to steal resources
PCI: Reassign BARs if BIOS/bootloader had assigned not all of them
PCI: Movable BARs: Make just a single attempt to assign bridge
resources
PCI: hotplug: Calculate fixed parts of bridge windows
PCI: Include fixed BARs into the bus size calculating
PCI: Make sure bridge windows include their fixed BARs
PCI: hotplug: Add support of fixed BARs to pci_assign_resource()
PCI: hotplug: Sort fixed BARs before assignment
x86/PCI/ACPI: Fix up PCIBIOS_MIN_MEM if value computed from e820 is
invalid
PCI: hotplug: Configure MPS after manual bus rescan
PCI: hotplug: Don't disable the released bridge windows immediately
PCI: pciehp: Trigger a domain rescan on hp events when enabled movable
BARs
PCI: Don't claim fixed BARs
PCI: hotplug: Retry bus assignment without reserved space
PCI: Rescan the bus to resize a BAR
PCI: hotplug: Enable the movable BARs feature by default
PCI/portdrv: Declare support of movable BARs
nvme-pci: Handle movable BARs
PCI: Add a message for updating BARs
resource: increase max nesting level for /proc/iomem
Documentation/PCI/pci.rst | 63 +++
.../admin-guide/kernel-parameters.txt | 1 +
arch/powerpc/platforms/powernv/pci.c | 2 +
arch/powerpc/platforms/pseries/setup.c | 2 +
arch/x86/pci/acpi.c | 15 +
drivers/nvme/host/pci.c | 27 +-
drivers/pci/bus.c | 2 +-
drivers/pci/hotplug/pciehp_pci.c | 5 +
drivers/pci/iov.c | 2 +
drivers/pci/pci.c | 24 ++
drivers/pci/pci.h | 34 ++
drivers/pci/pcie/portdrv_pci.c | 7 +
drivers/pci/probe.c | 401 +++++++++++++++++-
drivers/pci/setup-bus.c | 227 +++++++---
drivers/pci/setup-res.c | 105 ++++-
include/linux/pci.h | 16 +
kernel/resource.c | 2 +-
17 files changed, 863 insertions(+), 72 deletions(-)
base-commit: a409ed156a90093a03fe6a93721ddf4c591eac87
--
2.24.1
