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Subject[RFC PATCH] kdump: Add support for crashkernel=auto
Date
Set the reserved memory automatically for the crash kernel based on
architecture.

Most code of this patch come from:
https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-8/-/tree/c8s

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
Documentation/admin-guide/kdump/kdump.rst | 13 +++++++++++++
Documentation/admin-guide/kernel-parameters.txt | 5 +++++
kernel/crash_core.c | 20 ++++++++++++++++++++
3 files changed, 38 insertions(+)

diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
index cb30ca3d..8f8a9cc 100644
--- a/Documentation/admin-guide/kdump/kdump.rst
+++ b/Documentation/admin-guide/kdump/kdump.rst
@@ -335,6 +335,19 @@ crashkernel syntax

crashkernel=0,low

+4) crashkernel=auto
+
+ You can use crashkernel=auto if you have enough memory. The threshold
+ is 1G on x86_64 and s390x, 2G on arm64, ppc64 and ppc64le. If your system
+ memory is less than the threshold crashkernel=auto will not reserve memory.
+
+ The automatically reserved memory size varies based on architecture.
+ The size changes according to system memory size like below:
+ x86_64: 1G-4G:160M,4G-64G:192M,64G-1T:256M,1T-:512M
+ s390x: 1G-4G:160M,4G-64G:192M,64G-1T:256M,1T-:512M
+ arm64: 2G-:448M
+ ppc64: 2G-4G:384M,4G-16G:512M,16G-64G:1G,64G-128G:2G,128G-:4G
+
Boot into System Kernel
-----------------------
1) Update the boot loader (such as grub, yaboot, or lilo) configuration
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f5a27f0..14f052d 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -783,6 +783,11 @@
Format:
<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]

+ crashkernel=auto
+ [KNL] Set the reserved memory automatically for the crash kernel
+ based on architecture.
+ See Documentation/admin-guide/kdump/kdump.rst for further details.
+
crashkernel=size[KMG][@offset[KMG]]
[KNL] Using kexec, Linux can switch to a 'crash kernel'
upon panic. This parameter reserves the physical
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 256cf6d..32c51e2 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -252,6 +252,26 @@ static int __init __parse_crashkernel(char *cmdline,
if (suffix)
return parse_crashkernel_suffix(ck_cmdline, crash_size,
suffix);
+
+ if (strncmp(ck_cmdline, "auto", 4) == 0) {
+#if defined(CONFIG_X86_64) || defined(CONFIG_S390)
+ ck_cmdline = "1G-4G:160M,4G-64G:192M,64G-1T:256M,1T-:512M";
+#elif defined(CONFIG_ARM64)
+ ck_cmdline = "2G-:448M";
+#elif defined(CONFIG_PPC64)
+ char *fadump_cmdline;
+
+ fadump_cmdline = get_last_crashkernel(cmdline, "fadump=", NULL);
+ fadump_cmdline = fadump_cmdline ?
+ fadump_cmdline + strlen("fadump=") : NULL;
+ if (!fadump_cmdline || (strncmp(fadump_cmdline, "off", 3) == 0))
+ ck_cmdline = "2G-4G:384M,4G-16G:512M,16G-64G:1G,64G-128G:2G,128G-:4G";
+ else
+ ck_cmdline = "4G-16G:768M,16G-64G:1G,64G-128G:2G,128G-1T:4G,1T-2T:6G,2T-4T:12G,4T-8T:20G,8T-16T:36G,16T-32T:64G,32T-64T:128G,64T-:180G";
+#endif
+ pr_info("Using crashkernel=auto, the size chosen is a best effort estimation.\n");
+ }
+
/*
* if the commandline contains a ':', then that's the extended
* syntax -- if not, it must be the classic syntax
--
2.1.0
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