linux-kernel - Re: [patch 1/2] kdump: Initialize vmcoreinfo note at startup

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Date:	Thu, 15 Sep 2011 14:46:37 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Michael Holzheu <holzheu@...ux.vnet.ibm.com>
Cc:	ebiederm@...ssion.com, mahesh@...ux.vnet.ibm.com,
	schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-s390@...r.kernel.org
Subject: Re: [patch 1/2] kdump: Initialize vmcoreinfo note at startup

On Fri, Sep 09, 2011 at 12:27:00PM +0200, Michael Holzheu wrote:
> From: Michael Holzheu <holzheu@...ux.vnet.ibm.com>
> 
> Currently the vmcoreinfo note is only initialized in case of kdump. On s390
> it is possible to create kernel dumps with other dump mechanisms than kdump
> (e.g. via hypervisor dump or stand-alone dump tools).

Both of these will be invoked through panic notifiers because kdump kernel
is not loaded?

>For those dumps it
> would also be desirable to include the vmcoreinfo data.

Curious that how these two dump schemes make use vmcoreinfo data?

> To accomplish this,
> with this patch the vmcoreinfo ELF note is always initialized, not only in
> case of a (kdump) crash. On s390 we will add an ABI defined pointer at
> a well known address to vmcoreinfo so that dump analysis tools are able to
> find this information.

Instead of this, why don't you initialize the notes in your arch specific
call. IOW, why don't you give a call to crash_save_vmcoreinfo() in stand
alone dump path to prepare the note and then continue with stand alone
dump.

Thanks
Vivek

> 
> Signed-off-by: Michael Holzheu <holzheu@...ux.vnet.ibm.com>
> ---
>  kernel/kexec.c |   18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 
> --- a/kernel/kexec.c
> +++ b/kernel/kexec.c
> @@ -1392,24 +1392,23 @@ int __init parse_crashkernel(char 		 *cm
>  }
>  
>  
> -
> -void crash_save_vmcoreinfo(void)
> +static void update_vmcoreinfo_note(void)
>  {
> -	u32 *buf;
> +	u32 *buf = (u32 *) vmcoreinfo_note;
>  
>  	if (!vmcoreinfo_size)
>  		return;
> -
> -	vmcoreinfo_append_str("CRASHTIME=%ld", get_seconds());
> -
> -	buf = (u32 *)vmcoreinfo_note;
> -
>  	buf = append_elf_note(buf, VMCOREINFO_NOTE_NAME, 0, vmcoreinfo_data,
>  			      vmcoreinfo_size);
> -
>  	final_note(buf);
>  }
>  
> +void crash_save_vmcoreinfo(void)
> +{
> +	vmcoreinfo_append_str("CRASHTIME=%ld", get_seconds());
> +	update_vmcoreinfo_note();
> +}
> +
>  void vmcoreinfo_append_str(const char *fmt, ...)
>  {
>  	va_list args;
> @@ -1495,6 +1494,7 @@ static int __init crash_save_vmcoreinfo_
>  	VMCOREINFO_NUMBER(PG_swapcache);
>  
>  	arch_crash_save_vmcoreinfo();
> +	update_vmcoreinfo_note();
>  
>  	return 0;
>  }
--
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