On 07.05.21 03:04, Andrew Morton wrote:
From: Saeed Mirzamohammadi <saeed.mirzamohammadi@xxxxxxxxxx>
Subject: kernel/crash_core: add crashkernel=auto for vmcore creation
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.
Link: https://lkml.kernel.org/r/20210223174153.72802-1-saeed.mirzamohammadi@xxxxxxxxxx
Signed-off-by: Saeed Mirzamohammadi <saeed.mirzamohammadi@xxxxxxxxxx>
Signed-off-by: John Donnelly <john.p.donnelly@xxxxxxxxxx>
Tested-by: John Donnelly <john.p.donnelly@xxxxxxxxxx>
ed-by: Dave Young <dyoung@xxxxxxxxxx>
Cc: Baoquan He <bhe@xxxxxxxxxx>
Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: "Guilherme G. Piccoli" <gpiccoli@xxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
Cc: YiFei Zhu <yifeifz2@xxxxxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxx>
Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Cc: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
Cc: Frederic Weisbecker <frederic@xxxxxxxxxx>
Cc: Christian Brauner <christian.brauner@xxxxxxxxxx>
Cc: Stephen Boyd <sboyd@xxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Cc: Colin Ian King <colin.king@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/admin-guide/kdump/kdump.rst | 3 +-
Documentation/admin-guide/kernel-parameters.txt | 6 ++++
arch/Kconfig | 20 ++++++++++++++
kernel/crash_core.c | 7 ++++
4 files changed, 35 insertions(+), 1 deletion(-)
--- a/arch/Kconfig~kernel-crash_core-add-crashkernel=auto-for-vmcore-creation
+++ a/arch/Kconfig
@@ -14,6 +14,26 @@ menu "General architecture-dependent opt
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
--- a/Documentation/admin-guide/kdump/kdump.rst~kernel-crash_core-add-crashkernel=auto-for-vmcore-creation
+++ a/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
=======================
--- a/Documentation/admin-guide/kernel-parameters.txt~kernel-crash_core-add-crashkernel=auto-for-vmcore-creation
+++ a/Documentation/admin-guide/kernel-parameters.txt
@@ -751,6 +751,12 @@
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
--- a/kernel/crash_core.c~kernel-crash_core-add-crashkernel=auto-for-vmcore-creation
+++ a/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(ch
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
I remember that the original "crashkernel=auto" as once proposed by Red
Hat people did not receive a warm welcome.
Let me take a look .... oh, there it is from 2009
https://marc.info/?t=125006512600002&r=1&w=2
and then we had it in 2018
https://lkml.org/lkml/2018/5/20/262
The issue I have with this: it's just plain wrong when you take memory
hotplug into serious account as we see it quite heavily in VMs. You
don't know what you'll need when building a kernel. Just pass it via the
cmdline ...
--
Thanks,
David / dhildenb
