Documentation: Improve crash_kexec_post_notifiers description

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 a11589563e96 ("x86/Hyper-V: Report crash register data or kmsg before running crash kernel").
[1] Commit 06e629c25daa ("powerpc/fadump: Fix inaccurate CPU state info in vmcore generated with panic").
[2] Commit 8ef979584ea8 ("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

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 3978fb704c53a613d3c9ee2fc8b8257bfeb904f0..1dbd0b0df6fe3be7f9ceab274b2cdf710139fc14 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -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'