Re: [PATCH v4 1/1] kernel/crash_core: Add crashkernel=auto for vmcore creation

Dave Young
2021-02-26T00:40:58Z

On 02/23/21 at 09:41am, Saeed Mirzamohammadi wrote:
> 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
>

Acked-by: Dave Young <dyoung@redhat.com>

Thanks
Dave