[PATCH v3 1/1] kernel/crash_core: Add crashkernel=auto for vmcore creation

[PATCH v3 1/1] kernel/crash_core: Add crashkernel=auto for vmcore creation

[Saeed Mirzamohammadi]

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                                  | 24 +++++++++++++++++++
 kernel/crash_core.c                           |  7 ++++++
 4 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
index 2da65fef2a1c..e55cdc404c6b 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 7d4e523646c3..aa2099465458 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -736,6 +736,12 @@
 			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 af14a567b493..f87c88ffa2f8 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -14,6 +14,30 @@ menu "General architecture-dependent options"
 config CRASH_CORE
 	bool
 
+if CRASH_CORE
+
+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
+
+endif # CRASH_CORE
+
 config KEXEC_CORE
 	select CRASH_CORE
 	bool
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 106e4500fd53..ab0a2b4b1ffa 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

Re: [PATCH v3 1/1] kernel/crash_core: Add crashkernel=auto for vmcore creation

[john.p.donnelly]

On 2/11/21 12:08 PM, 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                                  | 24 +++++++++++++++++++
>   kernel/crash_core.c                           |  7 ++++++
>   4 files changed, 39 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
> index 2da65fef2a1c..e55cdc404c6b 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 7d4e523646c3..aa2099465458 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -736,6 +736,12 @@
>   			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 af14a567b493..f87c88ffa2f8 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -14,6 +14,30 @@ menu "General architecture-dependent options"
>   config CRASH_CORE
>   	bool
>   
> +if CRASH_CORE
> +
> +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
> +
> +endif # CRASH_CORE
> +
>   config KEXEC_CORE
>   	select CRASH_CORE
>   	bool
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index 106e4500fd53..ab0a2b4b1ffa 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
> 


Hello.

Ping.

Can we get this reviewed and staged ?

Thank you.

John.

Re: [PATCH v3 1/1] kernel/crash_core: Add crashkernel=auto for vmcore creation

[Steven Rostedt]

On Wed, 17 Feb 2021 12:40:43 -0600
john.p.donnelly@oracle.com wrote:

> Hello.
> 
> Ping.
> 
> Can we get this reviewed and staged ?
> 
> Thank you.

Andrew,

Seems you are the only one pushing patches in for kexec/crash. Is this
maintained by anyone?

-- Steve

Re: [PATCH v3 1/1] kernel/crash_core: Add crashkernel=auto for vmcore creation

[Vivek Goyal]

On Wed, Feb 17, 2021 at 02:26:53PM -0500, Steven Rostedt wrote:
> On Wed, 17 Feb 2021 12:40:43 -0600
> john.p.donnelly@oracle.com wrote:
> 
> > Hello.
> > 
> > Ping.
> > 
> > Can we get this reviewed and staged ?
> > 
> > Thank you.
> 
> Andrew,
> 
> Seems you are the only one pushing patches in for kexec/crash. Is this
> maintained by anyone?

Dave Young and Baoquan He still maintain kexec/kdump stuff, AFAIK. I
don't get time to look into this stuff now a days. 

Vivek

Re: [PATCH v3 1/1] kernel/crash_core: Add crashkernel=auto for vmcore creation

[Dave Young]

On 02/11/21 at 10:08am, 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                                  | 24 +++++++++++++++++++
>  kernel/crash_core.c                           |  7 ++++++
>  4 files changed, 39 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
> index 2da65fef2a1c..e55cdc404c6b 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 7d4e523646c3..aa2099465458 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -736,6 +736,12 @@
>  			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 af14a567b493..f87c88ffa2f8 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -14,6 +14,30 @@ menu "General architecture-dependent options"
>  config CRASH_CORE
>  	bool
>  
> +if CRASH_CORE
> +
> +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
> +
> +endif # CRASH_CORE
> +
>  config KEXEC_CORE
>  	select CRASH_CORE
>  	bool
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index 106e4500fd53..ab0a2b4b1ffa 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

Re: [PATCH v3 1/1] kernel/crash_core: Add crashkernel=auto for vmcore creation

[Dave Young]

On 02/17/21 at 02:42pm, Vivek Goyal wrote:
> On Wed, Feb 17, 2021 at 02:26:53PM -0500, Steven Rostedt wrote:
> > On Wed, 17 Feb 2021 12:40:43 -0600
> > john.p.donnelly@oracle.com wrote:
> > 
> > > Hello.
> > > 
> > > Ping.
> > > 
> > > Can we get this reviewed and staged ?
> > > 
> > > Thank you.
> > 
> > Andrew,
> > 
> > Seems you are the only one pushing patches in for kexec/crash. Is this
> > maintained by anyone?
> 
> Dave Young and Baoquan He still maintain kexec/kdump stuff, AFAIK. I
> don't get time to look into this stuff now a days. 

Vivek, no problem, both Baoquan and me are on holiday leaves previously.

I'm fine with the change. 
This patch benefits distributions and those people who want to deploy a lot of
machines.  It is a good start and we can continue to improve the estimation later.

Thanks
Dave 

Re: [PATCH v3 1/1] kernel/crash_core: Add crashkernel=auto for vmcore creation

[Baoquan He]

On 02/11/21 at 10:08am, 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                                  | 24 +++++++++++++++++++
>  kernel/crash_core.c                           |  7 ++++++
>  4 files changed, 39 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
> index 2da65fef2a1c..e55cdc404c6b 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 7d4e523646c3..aa2099465458 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -736,6 +736,12 @@
>  			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 af14a567b493..f87c88ffa2f8 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -14,6 +14,30 @@ menu "General architecture-dependent options"
>  config CRASH_CORE
>  	bool
>  
> +if CRASH_CORE
> +
> +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
> +
> +endif # CRASH_CORE

Wondering if this CRASH_CORE ifdeffery is a little redundent here
since CRASH_CORE dependency has been added. Except of this, I like this
patch. As we discussed in private threads, we can try to push it into
mainline and continue improving later.


> +
>  config KEXEC_CORE
>  	select CRASH_CORE
>  	bool
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index 106e4500fd53..ab0a2b4b1ffa 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
> 

Re: [PATCH v3 1/1] kernel/crash_core: Add crashkernel=auto for vmcore creation

[john.p.donnelly]

On 2/17/21 8:02 PM, Baoquan He wrote:
> On 02/11/21 at 10:08am, 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                                  | 24 +++++++++++++++++++
>>   kernel/crash_core.c                           |  7 ++++++
>>   4 files changed, 39 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
>> index 2da65fef2a1c..e55cdc404c6b 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 7d4e523646c3..aa2099465458 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -736,6 +736,12 @@
>>   			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 af14a567b493..f87c88ffa2f8 100644
>> --- a/arch/Kconfig
>> +++ b/arch/Kconfig
>> @@ -14,6 +14,30 @@ menu "General architecture-dependent options"
>>   config CRASH_CORE
>>   	bool
>>   
>> +if CRASH_CORE
>> +
>> +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
>> +
>> +endif # CRASH_CORE
> 
> Wondering if this CRASH_CORE ifdeffery is a little redundent here
> since CRASH_CORE dependency has been added. Except of this, I like this
> patch. As we discussed in private threads, we can try to push it into
> mainline and continue improving later.

Hi,

Are we good to move forward with this and apply it now?

Dave Young acked it.

Thank you,

John.

(Note - I am currently not on any vger.kernel.org dlist at the moment so 
please cc me ).



> 
> 
>> +
>>   config KEXEC_CORE
>>   	select CRASH_CORE
>>   	bool
>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
>> index 106e4500fd53..ab0a2b4b1ffa 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
>>
> 

Re: [PATCH v3 1/1] kernel/crash_core: Add crashkernel=auto for vmcore creation

[Kairui Song]

On Thu, Feb 18, 2021 at 10:03 AM Baoquan He <bhe@redhat.com> wrote:
>
> On 02/11/21 at 10:08am, 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                                  | 24 +++++++++++++++++++
> >  kernel/crash_core.c                           |  7 ++++++
> >  4 files changed, 39 insertions(+), 1 deletion(-)
> >
> > diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
> > index 2da65fef2a1c..e55cdc404c6b 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 7d4e523646c3..aa2099465458 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -736,6 +736,12 @@
> >                       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 af14a567b493..f87c88ffa2f8 100644
> > --- a/arch/Kconfig
> > +++ b/arch/Kconfig
> > @@ -14,6 +14,30 @@ menu "General architecture-dependent options"
> >  config CRASH_CORE
> >       bool
> >
> > +if CRASH_CORE
> > +
> > +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
> > +
> > +endif # CRASH_CORE
>
> Wondering if this CRASH_CORE ifdeffery is a little redundent here
> since CRASH_CORE dependency has been added. Except of this, I like this
> patch. As we discussed in private threads, we can try to push it into
> mainline and continue improving later.
>

I believe "if CRASH_CORE" is not needed as it already "depends on
CRASH_CORE", tested with CRASH_CORE=y or 'not set', it just works.

> > +
> >  config KEXEC_CORE
> >       select CRASH_CORE
> >       bool
> > diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> > index 106e4500fd53..ab0a2b4b1ffa 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
> >
>
>
> _______________________________________________
> kexec mailing list
> kexec@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec
>


-- 
Best Regards,
Kairui Song

Re: [PATCH v3 1/1] kernel/crash_core: Add crashkernel=auto for vmcore creation

[Baoquan He]

On 02/23/21 at 08:01pm, Kairui Song wrote:
> On Thu, Feb 18, 2021 at 10:03 AM Baoquan He <bhe@redhat.com> wrote:
> >
> > On 02/11/21 at 10:08am, Saeed Mirzamohammadi wrote:
...
> > > diff --git a/arch/Kconfig b/arch/Kconfig
> > > index af14a567b493..f87c88ffa2f8 100644
> > > --- a/arch/Kconfig
> > > +++ b/arch/Kconfig
> > > @@ -14,6 +14,30 @@ menu "General architecture-dependent options"
> > >  config CRASH_CORE
> > >       bool
> > >
> > > +if CRASH_CORE
> > > +
> > > +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
> > > +
> > > +endif # CRASH_CORE
> >
> > Wondering if this CRASH_CORE ifdeffery is a little redundent here
> > since CRASH_CORE dependency has been added. Except of this, I like this
> > patch. As we discussed in private threads, we can try to push it into
> > mainline and continue improving later.
> >
> 
> I believe "if CRASH_CORE" is not needed as it already "depends on
> CRASH_CORE", tested with CRASH_CORE=y or 'not set', it just works.

Thanks for testing and confirmation, Kairui.

Saeed, can you post a v4 with CRASH_CORE ifdeffery removed? Maybe this
week?

Thanks
Baoquan

> 
> > > +
> > >  config KEXEC_CORE
> > >       select CRASH_CORE
> > >       bool
> > > diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> > > index 106e4500fd53..ab0a2b4b1ffa 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
> > >
> >
> >
> > _______________________________________________
> > kexec mailing list
> > kexec@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/kexec
> >
> 
> 
> -- 
> Best Regards,
> Kairui Song
> 

Re: [PATCH v3 1/1] kernel/crash_core: Add crashkernel=auto for vmcore creation

[Saeed Mirzamohammadi]

> On Feb 23, 2021, at 5:56 AM, Baoquan He <bhe@redhat.com> wrote:
> 
> On 02/23/21 at 08:01pm, Kairui Song wrote:
>> On Thu, Feb 18, 2021 at 10:03 AM Baoquan He <bhe@redhat.com> wrote:
>>> 
>>> On 02/11/21 at 10:08am, Saeed Mirzamohammadi wrote:
> ...
>>>> diff --git a/arch/Kconfig b/arch/Kconfig
>>>> index af14a567b493..f87c88ffa2f8 100644
>>>> --- a/arch/Kconfig
>>>> +++ b/arch/Kconfig
>>>> @@ -14,6 +14,30 @@ menu "General architecture-dependent options"
>>>> config CRASH_CORE
>>>>      bool
>>>> 
>>>> +if CRASH_CORE
>>>> +
>>>> +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
>>>> +
>>>> +endif # CRASH_CORE
>>> 
>>> Wondering if this CRASH_CORE ifdeffery is a little redundent here
>>> since CRASH_CORE dependency has been added. Except of this, I like this
>>> patch. As we discussed in private threads, we can try to push it into
>>> mainline and continue improving later.
>>> 
>> 
>> I believe "if CRASH_CORE" is not needed as it already "depends on
>> CRASH_CORE", tested with CRASH_CORE=y or 'not set', it just works.
> 
> Thanks for testing and confirmation, Kairui.
> 
> Saeed, can you post a v4 with CRASH_CORE ifdeffery removed? Maybe this
> week?

Thanks Kairui and Baoquan for testing and review. I just sent the v4. Hope we move forward and apply this week.

Saeed

> 
> Thanks
> Baoquan
> 
>> 
>>>> +
>>>> config KEXEC_CORE
>>>>      select CRASH_CORE
>>>>      bool
>>>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
>>>> index 106e4500fd53..ab0a2b4b1ffa 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
>>>> 
>>> 
>>> 
>>> _______________________________________________
>>> kexec mailing list
>>> kexec@lists.infradead.org
>>> https://urldefense.com/v3/__http://lists.infradead.org/mailman/listinfo/kexec__;!!GqivPVa7Brio!MaBAPZr-j_WcNPodmosfVOyl0ipO6u22Ex-7gSi--wlwbmTgmkhsf-0yftioew3jnkS5WV5v$ 
>>> 
>> 
>> 
>> -- 
>> Best Regards,
>> Kairui Song
>> 
> 

Re: [PATCH v3 1/1] kernel/crash_core: Add crashkernel=auto for vmcore creation

[Baoquan He]

On 02/11/21 at 10:08am, 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                                  | 24 +++++++++++++++++++
>  kernel/crash_core.c                           |  7 ++++++
>  4 files changed, 39 insertions(+), 1 deletion(-)

Acked-by: Baoquan He <bhe@redhat.com>

> 
> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
> index 2da65fef2a1c..e55cdc404c6b 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 7d4e523646c3..aa2099465458 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -736,6 +736,12 @@
>  			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 af14a567b493..f87c88ffa2f8 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -14,6 +14,30 @@ menu "General architecture-dependent options"
>  config CRASH_CORE
>  	bool
>  
> +if CRASH_CORE
> +
> +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
> +
> +endif # CRASH_CORE
> +
>  config KEXEC_CORE
>  	select CRASH_CORE
>  	bool
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index 106e4500fd53..ab0a2b4b1ffa 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
> 

Re: [PATCH v3 1/1] kernel/crash_core: Add crashkernel=auto for vmcore creation

[Baoquan He]

On 02/24/21 at 09:54am, Baoquan He wrote:
> On 02/11/21 at 10:08am, 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                                  | 24 +++++++++++++++++++
> >  kernel/crash_core.c                           |  7 ++++++
> >  4 files changed, 39 insertions(+), 1 deletion(-)
> 
> Acked-by: Baoquan He <bhe@redhat.com>

Sorry, I just acked on wrong version of patch, please ignore this.

> 
> > 
> > diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
> > index 2da65fef2a1c..e55cdc404c6b 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 7d4e523646c3..aa2099465458 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -736,6 +736,12 @@
> >  			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 af14a567b493..f87c88ffa2f8 100644
> > --- a/arch/Kconfig
> > +++ b/arch/Kconfig
> > @@ -14,6 +14,30 @@ menu "General architecture-dependent options"
> >  config CRASH_CORE
> >  	bool
> >  
> > +if CRASH_CORE
> > +
> > +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
> > +
> > +endif # CRASH_CORE
> > +
> >  config KEXEC_CORE
> >  	select CRASH_CORE
> >  	bool
> > diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> > index 106e4500fd53..ab0a2b4b1ffa 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
> >