If the firmware or kernel has arranged memory for PCIe devices in a way that doesn't provide enough space for BARs of a new hotplugged device, the kernel can pause the drivers of the "obstructing" devices and move their BARs, so new BARs can fit into the freed spaces. When a driver is un-paused by the kernel after the PCIe rescan, it should check if its BARs had moved, and ioremap() them if needed. Drivers indicate their support of the feature by implementing the new rescan_prepare() and rescan_done() hooks in the struct pci_driver. If a driver doesn't yet support the feature, BARs of its devices will be marked as immovable by the IORESOURCE_PCI_FIXED flag. To re-arrange the BARs and bridge windows this patch releases all of them after a rescan and re-assigns in the same way as during the initial PCIe topology scan at system boot. Tested on: - x86_64 with "pci=realloc,assign-busses,use_crs pcie_movable_bars=force" - POWER8 PowerNV+PHB3 ppc64le with [1] and [2] applied and the following: "pci=realloc pcie_movable_bars=force" Not so many platforms and test cases were covered, so all who are interested are highly welcome to test on your setups - the more exotic the better! This patchset is a part of our work on adding support for hotplugging bridges full of NVME and GPU devices without special requirements such as Hot-Plug Controller, reservation of bus numbers or memory regions by firmware, etc. Future work will be devoted to implementing the movable bus numbers. [1] https://lists.ozlabs.org/pipermail/linuxppc-dev/2019-March/186618.html [2] https://lists.ozlabs.org/pipermail/skiboot/2019-March/013571.html 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. Sergey Miroshnichenko (21): PCI: Fix writing invalid BARs during pci_restore_state() PCI: Fix race condition in pci_enable/disable_device() PCI: Enable bridge's I/O and MEM access for hotplugged devices PCI: Define PCI-specific version of the release_child_resources() PCI: hotplug: Add a flag for the movable BARs feature PCI: Pause the devices with movable BARs during rescan PCI: Wake up bridges during rescan when movable BARs enabled nvme-pci: Handle movable BARs PCI: Mark immovable BARs with PCI_FIXED PCI: Fix assigning of fixed prefetchable resources PCI: Release and reassign the root bridge resources during rescan PCI: Don't allow hotplugged devices to steal resources PCI: Include fixed BARs into the bus size calculating PCI: Don't reserve memory for hotplug when enabled movable BARs PCI: Allow the failed resources to be reassigned later PCI: Calculate fixed areas of bridge windows based on fixed BARs PCI: Calculate boundaries for bridge windows PCI: Make sure bridge windows include their fixed BARs PCI: Prioritize fixed BAR assigning over the movable ones PCI: pciehp: Add support for the movable BARs feature powerpc/pci: Fix crash with enabled movable BARs .../admin-guide/kernel-parameters.txt | 7 + arch/powerpc/platforms/powernv/pci-ioda.c | 3 +- drivers/nvme/host/pci.c | 29 +- drivers/pci/bus.c | 7 +- drivers/pci/hotplug/pciehp_pci.c | 14 +- drivers/pci/pci.c | 60 +++- drivers/pci/pci.h | 26 ++ drivers/pci/probe.c | 271 +++++++++++++++++- drivers/pci/setup-bus.c | 245 ++++++++++++++-- drivers/pci/setup-res.c | 43 ++- include/linux/pci.h | 14 + 11 files changed, 678 insertions(+), 41 deletions(-) -- 2.20.1
