[PATCH 1/1] kernel/crash_core.c - Add crashkernel=auto for x86 and ARM

From: Saeed Mirzamohammadi
Date: Wed Nov 18 2020 - 18:28:53 EST

This adds crashkernel=auto feature to configure reserved memory for
vmcore creation to both x86 and ARM platforms based on the total memory
size.

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: John Donnelly <john.p.donnelly@xxxxxxxxxx>
Signed-off-by: Saeed Mirzamohammadi <saeed.mirzamohammadi@xxxxxxxxxx>
---
Documentation/admin-guide/kdump/kdump.rst | 5 +++++
arch/arm64/Kconfig | 26 ++++++++++++++++++++++-
arch/arm64/configs/defconfig | 1 +
arch/x86/Kconfig | 26 ++++++++++++++++++++++-
arch/x86/configs/x86_64_defconfig | 1 +
kernel/crash_core.c | 20 +++++++++++++++--
6 files changed, 75 insertions(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
index 75a9dd98e76e..f95a2af64f59 100644
--- a/Documentation/admin-guide/kdump/kdump.rst
+++ b/Documentation/admin-guide/kdump/kdump.rst
@@ -285,7 +285,12 @@ 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 if you have enough memory. The threshold
+is 1G on x86_64 and arm64. If your system memory is less than the threshold,
+crashkernel=auto will not reserve memory. The size changes according to
+the system memory size like below:

+ x86_64/arm64: 1G-64G:128M,64G-1T:256M,1T-:512M

Boot into System Kernel
=======================
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 1515f6f153a0..d359dcffa80e 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1124,7 +1124,7 @@ comment "Support for PE file signature verification disabled"
depends on KEXEC_SIG
depends on !EFI || !SIGNED_PE_FILE_VERIFICATION

-config CRASH_DUMP
+menuconfig CRASH_DUMP
bool "Build kdump crash kernel"
help
Generate crash dump after being started by kexec. This should
@@ -1135,6 +1135,30 @@ config CRASH_DUMP

For more details see Documentation/admin-guide/kdump/kdump.rst

+if CRASH_DUMP
+
+config CRASH_AUTO_STR
+ string "Memory reserved for crash kernel"
+ depends on CRASH_DUMP
+ 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
+
+endif # CRASH_DUMP
+
config XEN_DOM0
def_bool y
depends on XEN
diff --git a/arch/arm64/configs/defconfig b/arch/arm64/configs/defconfig
index 5cfe3cf6f2ac..899ef3b6a78f 100644
--- a/arch/arm64/configs/defconfig
+++ b/arch/arm64/configs/defconfig
@@ -69,6 +69,7 @@ CONFIG_SECCOMP=y
CONFIG_KEXEC=y
CONFIG_KEXEC_FILE=y
CONFIG_CRASH_DUMP=y
+# CONFIG_CRASH_AUTO_STR is not set
CONFIG_XEN=y
CONFIG_COMPAT=y
CONFIG_RANDOMIZE_BASE=y
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f6946b81f74a..bacd17312bb1 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2035,7 +2035,7 @@ config KEXEC_BZIMAGE_VERIFY_SIG
help
Enable bzImage signature verification support.

-config CRASH_DUMP
+menuconfig CRASH_DUMP
bool "kernel crash dumps"
depends on X86_64 || (X86_32 && HIGHMEM)
help
@@ -2049,6 +2049,30 @@ config CRASH_DUMP
(CONFIG_RELOCATABLE=y).
For more details see Documentation/admin-guide/kdump/kdump.rst

+if CRASH_DUMP
+
+config CRASH_AUTO_STR
+ string "Memory reserved for crash kernel" if X86_64
+ depends on CRASH_DUMP
+ 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
+
+endif # CRASH_DUMP
+
config KEXEC_JUMP
bool "kexec jump"
depends on KEXEC && HIBERNATION
diff --git a/arch/x86/configs/x86_64_defconfig b/arch/x86/configs/x86_64_defconfig
index 9936528e1939..7a87fbecf40b 100644
--- a/arch/x86/configs/x86_64_defconfig
+++ b/arch/x86/configs/x86_64_defconfig
@@ -33,6 +33,7 @@ CONFIG_EFI_MIXED=y
CONFIG_HZ_1000=y
CONFIG_KEXEC=y
CONFIG_CRASH_DUMP=y
+# CONFIG_CRASH_AUTO_STR is not set
CONFIG_HIBERNATION=y
CONFIG_PM_DEBUG=y
CONFIG_PM_TRACE_RTC=y
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 106e4500fd53..a44cd9cc12c4 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>
@@ -41,6 +42,15 @@ static int __init parse_crashkernel_mem(char *cmdline,
unsigned long long *crash_base)
{
char *cur = cmdline, *tmp;
+ unsigned long long total_mem = system_ram;
+
+ /*
+ * Firmware sometimes reserves some memory regions for it's own use.
+ * so we get less than actual system memory size.
+ * Workaround this by round up the total size to 128M which is
+ * enough for most test cases.
+ */
+ total_mem = roundup(total_mem, SZ_128M);

/* for each entry of the comma-separated list */
do {
@@ -85,13 +95,13 @@ static int __init parse_crashkernel_mem(char *cmdline,
return -EINVAL;
}
cur = tmp;
- if (size >= system_ram) {
+ if (size >= total_mem) {
pr_warn("crashkernel: invalid size\n");
return -EINVAL;
}

/* match ? */
- if (system_ram >= start && system_ram < end) {
+ if (total_mem >= start && total_mem < end) {
*crash_size = size;
break;
}
@@ -250,6 +260,12 @@ 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
--
2.18.4