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    Subject[PATCH 1/1] kernel/crash_core.c - Add crashkernel=auto for x86 and ARM
    Date
    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@vger.kernel.org
    Signed-off-by: John Donnelly <john.p.donnelly@oracle.com>
    Signed-off-by: Saeed Mirzamohammadi <saeed.mirzamohammadi@oracle.com>
    ---
    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
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