From 810b726b82c3ed2125ac1c5dd93532057135ea12 Mon Sep 17 00:00:00 2001 From: Tao Liu Date: May 31 2024 05:27:37 +0000 Subject: sysconfig: add pcie_ports compat to KDUMP_COMMANDLINE_APPEND on x86_64 Upstream: fedora Resolves: RHEL-3929 Conflict: Yes, for fedora there is no kdump.sysconfig.x86_64, but gen-kdump-sysconfig.sh. So for backporting, the modification is made on kdump.sysconfig.x86_64. commit ada6f5edf1ae06fc88759aa2f94d09e2a98d21ef Author: Tao Liu Date: Wed May 1 16:53:19 2024 +0800 sysconfig: add pcie_ports compat to KDUMP_COMMANDLINE_APPEND on x86_64 There have been some of failing cases of kdump in 2nd kernel, where ususally only one cpu is enabled by "nr_cpus=1", but with a large number of devices, which may easily exceed the maximum IRQ resources of one cpu can handle. As a result, the 2nd kernel will hang and kdump fails. This issue is often observed on machines with many cpus and many devices. On those systems, pcieports consume quite proportion of IRQ resources, many following message can be seen in dmesg log: pcieport 0000:18:01.0: PME: Signaling with IRQ 109 According to kernel doc[1], when "pcie_ports=compat" applied, it will disable native PCIe services (PME, AER, DPC, PCIe hotplug). Those functions are power management events, error reporting, performance, hotplug related, which are not the must-have functions for kdump. In addition, after testing, no side effects such as cannot writing vmcore into sdx, nvme etc been noticed. This patch will disable native PCIe services for 2nd kernel, to saving the scarce IRQ resources and increase the kdump success. Attach Prarit's comments: This makes sense to me. The only concern anyone should have is that a PCIE error could have been responsible for taking down the kernel in the first place, and booting into the second kernel could then also have a fatal problem. I'm not sure we can ever fix that type of cascade of panics :) so it makes sense to disable these features. [1]: https://www.kernel.org/doc/html/v6.9-rc1/admin-guide/kernel-parameters.html Signed-off-by: Tao Liu Acked-by: Prarit Bhargava Acked-by: Dave Young Signed-off-by: Tao Liu --- diff --git a/kdump.sysconfig.x86_64 b/kdump.sysconfig.x86_64 index 6a3ba6e..09d7350 100644 --- a/kdump.sysconfig.x86_64 +++ b/kdump.sysconfig.x86_64 @@ -21,7 +21,7 @@ KDUMP_COMMANDLINE_REMOVE="hugepages hugepagesz slub_debug quiet log_buf_len swio # This variable lets us append arguments to the current kdump commandline # after processed by KDUMP_COMMANDLINE_REMOVE -KDUMP_COMMANDLINE_APPEND="irqpoll nr_cpus=1 reset_devices cgroup_disable=memory mce=off numa=off udev.children-max=2 panic=10 acpi_no_memhotplug transparent_hugepage=never nokaslr hest_disable novmcoredd cma=0 hugetlb_cma=0" +KDUMP_COMMANDLINE_APPEND="irqpoll nr_cpus=1 reset_devices cgroup_disable=memory mce=off numa=off udev.children-max=2 panic=10 acpi_no_memhotplug transparent_hugepage=never nokaslr hest_disable novmcoredd cma=0 hugetlb_cma=0 pcie_ports=compat" # Any additional kexec arguments required. In most situations, this should # be left empty