Hi! I am facing an issue with PCIe-Hotplug on an AMD Epyc based system. Our system is equipped with an HBA for NVMe SSDs incl. PCIe switch (Supermicro AOC-SLG3-4E2P) [1] and we would like to be able to hotplug NVMe disks. Currently, I'm testing with v5.5.0-rc1 and series [2] applied. Here a few tests and results that I did so far. All tests were done with one Intel NVMe SSD connected to one of the 4 NVMe ports of the HBA and the other 3 ports (currently) left unconnected: a) Kernel Parameter "pci=pcie_bus_safe" The resources of the 3 unused PCIe slots of the PEX switch are not assigned in this test. b) Kernel Parameter "pci=pcie_bus_safe,hpmemsize=0,hpiosize=0,hpmmiosize=1M,hpmmioprefsize=0" With this test I restricted the resources of the HP slots to the minimum. Still this results in unassigned resourced for the unused PCIe slots of the PEX switch. c) Kernel Parameter "pci=realloc,pcie_bus_safe,hpmemsize=0,hpiosize=0,hpmmiosize=1M,hpmmioprefsize=0" Again, not all resources are assigned. d) Kernel Parameter "pci=nocrs,realloc,pcie_bus_safe,hpmemsize=0,hpiosize=0,hpmmiosize=1M,hpmmioprefsize=0" Now all requested resources are available for the HP PCIe slots of the PEX switch. But the NVMe driver fails while probing. Debugging has shown, that reading from the BAR of the NVMe disk returns 0xffffffff. Also reading from the PLX PEX switch registers returns 0xfffffff in this case (this works of course without nocrs, when the BARs are mapped at a different address). Does anybody have a clue on why the access to the PEX switch and / or the NVMe BAR does not work in the "nocrs" case? The BARs are located in the same window that is provided by the BIOS in the ACPI list (but is "ignored" in this case) [3]. Or if it is possible to get the HP resource mapping done correctly without setting "nocrs" for our setup with the PCIe/NVMe switch? I can provide all sorts of logs (dmegs, lspci etc) if needed - just let me know. Many thanks in advance, Stefan [1] https://www.supermicro.com/en/products/accessories/addon/AOC-SLG3-4E2P.php [2] https://lkml.org/lkml/2019/12/9/388 [3] [ 0.701932] acpi PNP0A08:00: host bridge window [io 0x0cf8-0x0cff] (ignored) [ 0.701934] acpi PNP0A08:00: host bridge window [io 0x0000-0x02ff window] (ignored) [ 0.701935] acpi PNP0A08:00: host bridge window [io 0x0300-0x03af window] (ignored) [ 0.701936] acpi PNP0A08:00: host bridge window [io 0x03e0-0x0cf7 window] (ignored) [ 0.701937] acpi PNP0A08:00: host bridge window [io 0x03b0-0x03df window] (ignored) [ 0.701938] acpi PNP0A08:00: host bridge window [io 0x0d00-0x3fff window] (ignored) [ 0.701939] acpi PNP0A08:00: host bridge window [mem 0x000a0000-0x000bffff window] (ignored) [ 0.701939] acpi PNP0A08:00: host bridge window [mem 0x000c0000-0x000dffff window] (ignored) [ 0.701940] acpi PNP0A08:00: host bridge window [mem 0xec000000-0xefffffff window] (ignored) [ 0.701941] acpi PNP0A08:00: host bridge window [mem 0x182c8000000-0x1ffffffffff window] (ignored) ... 41:00.0 PCI bridge: PLX Technology, Inc. PEX 9733 33-lane, 9-port PCI Express Gen 3 (8.0 GT/s) Switch (rev b0) (prog-if 00 [Normal decode]) Flags: bus master, fast devsel, latency 0, IRQ 47, NUMA node 2 Memory at ec400000 (32-bit, non-prefetchable) [size=256K] Bus: primary=41, secondary=42, subordinate=47, sec-latency=0 I/O behind bridge: None Memory behind bridge: ec000000-ec3fffff [size=4M] Prefetchable memory behind bridge: None Capabilities: <access denied> Kernel driver in use: pcieport epyc@epyc-Super-Server:~/stefan$ sudo ./memtool md 0xec400000+0x10 ec400000: ffffffff ffffffff ffffffff ffffffff ................
