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Documentation: Improve crash_kexec_post_notifiers description

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The crash_kexec_post_notifiers description could be improved a bit,
by clarifying its upsides (yes, there are some!) and be more descriptive
about the downsides, specially mentioning code that enables the option
unconditionally, like Hyper-V[0], PowerPC (fadump)[1] and more recently,
AMD SEV-SNP[2].

[0] Commit a11589563e ("x86/Hyper-V: Report crash register data or kmsg before running crash kernel").
[1] Commit 06e629c25d ("powerpc/fadump: Fix inaccurate CPU state info in vmcore generated with panic").
[2] Commit 8ef979584e ("crypto: ccp: Add panic notifier for SEV/SNP firmware shutdown on kdump").

Reviewed-by: Stephen Brennan <stephen.s.brennan@oracle.com>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20241027204159.985163-1-gpiccoli@igalia.com
This commit is contained in:
Guilherme G. Piccoli 2024-10-27 17:36:58 -03:00 committed by Jonathan Corbet
parent 6f33817fb4
commit 7d6094e62c
1 changed files with 10 additions and 6 deletions
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16
Documentation/admin-guide/kernel-parameters.txt
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@ -918,12 +918,16 @@
the parameter has no effect.
crash_kexec_post_notifiers
Run kdump after running panic-notifiers and dumping
kmsg. This only for the users who doubt kdump always
succeeds in any situation.
Note that this also increases risks of kdump failure,
because some panic notifiers can make the crashed
kernel more unstable.
Only jump to kdump kernel after running the panic
notifiers and dumping kmsg. This option increases
the risks of a kdump failure, since some panic
notifiers can make the crashed kernel more unstable.
In configurations where kdump may not be reliable,
running the panic notifiers could allow collecting
more data on dmesg, like stack traces from other CPUS
or extra data dumped by panic_print. Note that some
configurations enable this option unconditionally,
like Hyper-V, PowerPC (fadump) and AMD SEV-SNP.
crashkernel=size[KMG][@offset[KMG]]
[KNL,EARLY] Using kexec, Linux can switch to a 'crash kernel'