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Subject[PATCH v4 1/1] kernel/crash_core: Add crashkernel=auto for vmcore creation
Date
This adds crashkernel=auto feature to configure reserved memory for
vmcore creation. CONFIG_CRASH_AUTO_STR is defined to be set for
different kernel distributions and different archs based on their
needs.

Signed-off-by: Saeed Mirzamohammadi <saeed.mirzamohammadi@oracle.com>
Signed-off-by: John Donnelly <john.p.donnelly@oracle.com>
Tested-by: John Donnelly <john.p.donnelly@oracle.com>
---
Documentation/admin-guide/kdump/kdump.rst | 3 ++-
.../admin-guide/kernel-parameters.txt | 6 ++++++
arch/Kconfig | 20 +++++++++++++++++++
kernel/crash_core.c | 7 +++++++
4 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
index 75a9dd98e76e..ae030111e22a 100644
--- a/Documentation/admin-guide/kdump/kdump.rst
+++ b/Documentation/admin-guide/kdump/kdump.rst
@@ -285,7 +285,8 @@ This would mean:
2) if the RAM size is between 512M and 2G (exclusive), then reserve 64M
3) if the RAM size is larger than 2G, then reserve 128M

-
+Or you can use crashkernel=auto to choose the crash kernel memory size
+based on the recommended configuration set for each arch.

Boot into System Kernel
=======================
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 9e3cdb271d06..a5deda5c85fe 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -747,6 +747,12 @@
a memory unit (amount[KMG]). See also
Documentation/admin-guide/kdump/kdump.rst for an example.

+ crashkernel=auto
+ [KNL] This parameter will set the reserved memory for
+ the crash kernel based on the value of the CRASH_AUTO_STR
+ that is the best effort estimation for each arch. See also
+ arch/Kconfig for further details.
+
crashkernel=size[KMG],high
[KNL, X86-64] range could be above 4G. Allow kernel
to allocate physical memory region from top, so could
diff --git a/arch/Kconfig b/arch/Kconfig
index 24862d15f3a3..23d047548772 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -14,6 +14,26 @@ menu "General architecture-dependent options"
config CRASH_CORE
bool

+config CRASH_AUTO_STR
+ string "Memory reserved for crash kernel"
+ depends on CRASH_CORE
+ default "1G-64G:128M,64G-1T:256M,1T-:512M"
+ help
+ This configures the reserved memory dependent
+ on the value of System RAM. The syntax is:
+ crashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset]
+ range=start-[end]
+
+ For example:
+ crashkernel=512M-2G:64M,2G-:128M
+
+ This would mean:
+
+ 1) if the RAM is smaller than 512M, then don't reserve anything
+ (this is the "rescue" case)
+ 2) if the RAM size is between 512M and 2G (exclusive), then reserve 64M
+ 3) if the RAM size is larger than 2G, then reserve 128M
+
config KEXEC_CORE
select CRASH_CORE
bool
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 825284baaf46..90f9e4bb6704 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -7,6 +7,7 @@
#include <linux/crash_core.h>
#include <linux/utsname.h>
#include <linux/vmalloc.h>
+#include <linux/kexec.h>

#include <asm/page.h>
#include <asm/sections.h>
@@ -250,6 +251,12 @@ static int __init __parse_crashkernel(char *cmdline,
if (suffix)
return parse_crashkernel_suffix(ck_cmdline, crash_size,
suffix);
+#ifdef CONFIG_CRASH_AUTO_STR
+ if (strncmp(ck_cmdline, "auto", 4) == 0) {
+ ck_cmdline = CONFIG_CRASH_AUTO_STR;
+ pr_info("Using crashkernel=auto, the size chosen is a best effort estimation.\n");
+ }
+#endif
/*
* if the commandline contains a ':', then that's the extended
* syntax -- if not, it must be the classic syntax
--
2.27.0
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