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| author | Thomas Gleixner <tglx@linutronix.de> | 2024-02-14 00:05:54 +0300 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2024-02-16 00:07:43 +0300 |
| commit | 5c5682b9f87a3b7bd4833884f300ec673685f6a6 (patch) | |
| tree | 84273122a8fa878cb1237d0273a83fea3cc8cc1e /Documentation/admin-guide/kdump | |
| parent | 7c0edad3643f4493c4dafa6f5dfcfb1a86432156 (diff) | |
| download | linux-5c5682b9f87a3b7bd4833884f300ec673685f6a6.tar.xz | |
x86/cpu: Detect real BSP on crash kernels
When a kdump kernel is started from a crashing CPU then there is no
guarantee that this CPU is the real boot CPU (BSP). If the kdump kernel
tries to online the BSP then the INIT sequence will reset the machine.
There is a command line option to prevent this, but in case of nested kdump
kernels this is wrong.
But that command line option is not required at all because the real
BSP is enumerated as the first CPU by firmware. Support for the only
known system which was different (Voyager) got removed long ago.
Detect whether the boot CPU APIC ID is the first APIC ID enumerated by
the firmware. If the first APIC ID enumerated is not matching the boot
CPU APIC ID then skip registering it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20240213210252.348542071@linutronix.de
Diffstat (limited to 'Documentation/admin-guide/kdump')
| -rw-r--r-- | Documentation/admin-guide/kdump/kdump.rst | 7 |
1 files changed, 2 insertions, 5 deletions
diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst index 5762e7477a0c..0302a93b1d40 100644 --- a/Documentation/admin-guide/kdump/kdump.rst +++ b/Documentation/admin-guide/kdump/kdump.rst @@ -191,9 +191,7 @@ Dump-capture kernel config options (Arch Dependent, i386 and x86_64) CPU is enough for kdump kernel to dump vmcore on most of systems. However, you can also specify nr_cpus=X to enable multiple processors - in kdump kernel. In this case, "disable_cpu_apicid=" is needed to - tell kdump kernel which cpu is 1st kernel's BSP. Please refer to - admin-guide/kernel-parameters.txt for more details. + in kdump kernel. With CONFIG_SMP=n, the above things are not related. @@ -454,8 +452,7 @@ Notes on loading the dump-capture kernel: to use multi-thread programs with it, such as parallel dump feature of makedumpfile. Otherwise, the multi-thread program may have a great performance degradation. To enable multi-cpu support, you should bring up an - SMP dump-capture kernel and specify maxcpus/nr_cpus, disable_cpu_apicid=[X] - options while loading it. + SMP dump-capture kernel and specify maxcpus/nr_cpus options while loading it. * For s390x there are two kdump modes: If a ELF header is specified with the elfcorehdr= kernel parameter, it is used by the kdump kernel as it |