linux-kernel - Re: [PATCH v3 3/4] x86, kdump: Change crashkernel

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Date:	Tue, 9 Apr 2013 12:47:20 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Yinghai Lu <yinghai@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, WANG Chao <chaowang@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/4] x86, kdump: Change crashkernel_high/low= to
 crashkernel=;high/low

On Tue, Apr 09, 2013 at 08:00:57AM -0700, H. Peter Anvin wrote:
> Please, no semicolons. We already have established syntax for suboptions (option=suboption,suboption,...) and suboptions with parameters (option=suboption:value,...)

Ok, to understand it better, so crashkernel= will look as follows?

crashkernel=suboption[,suboption[,....]][@offset]

A suboption can be.

- A memory value (128[KMG])
- A range with value (range:size)
- Or a property influencing memory allocation behavior (e.g high or low)

If yes, sounds good.

Thanks
Vivek
 

> 
> Vivek Goyal <vgoyal@...hat.com> wrote:
> 
> >On Thu, Apr 04, 2013 at 03:17:01PM -0700, Yinghai Lu wrote:
> >
> >[..]
> >> @@ -1360,37 +1369,80 @@ static int __init parse_crashkernel_simp
> >>  
> >>  	if (*cur == '@')
> >>  		*crash_base = memparse(cur+1, &cur);
> >> -	else if (*cur != ' ' && *cur != '\0') {
> >> -		pr_warning("crashkernel: unrecognized char\n");
> >> -		return -EINVAL;
> >> +	else {
> >> +		int i;
> >> +
> >> +		/* check with known suffix */
> >> +		for (i = 0; suffix_tbl[i]; i++)
> >> +			if (!strncmp(cur, suffix_tbl[i], strlen(suffix_tbl[i])))
> >> +				return 0;
> >> +
> >
> >So crashkernel=X@Y;high is a valid syntax? Looks like we will reserve
> >X amount of RAM at base Y and ignore "high" or "low".
> >
> >[..]
> >>  static int __init __parse_crashkernel(char *cmdline,
> >>  			     unsigned long long system_ram,
> >>  			     unsigned long long *crash_size,
> >>  			     unsigned long long *crash_base,
> >> -				const char *name)
> >> +			     const char *name,
> >> +			     const char *suffix,
> >> +			     bool simple_only)
> >>  {
> >> -	char 	*p = cmdline, *ck_cmdline = NULL;
> >>  	char	*first_colon, *first_space;
> >> +	char	*ck_cmdline;
> >>  
> >>  	BUG_ON(!crash_size || !crash_base);
> >>  	*crash_size = 0;
> >>  	*crash_base = 0;
> >>  
> >> -	/* find crashkernel and use the last one if there are more */
> >> -	p = strstr(p, name);
> >> -	while (p) {
> >> -		ck_cmdline = p;
> >> -		p = strstr(p+1, name);
> >> -	}
> >> +	ck_cmdline = get_last_crashkernel(cmdline, name, suffix);
> >>  
> >>  	if (!ck_cmdline)
> >>  		return -EINVAL;
> >> @@ -1403,23 +1455,30 @@ static int __init __parse_crashkernel(ch
> >>  	 */
> >>  	first_colon = strchr(ck_cmdline, ':');
> >>  	first_space = strchr(ck_cmdline, ' ');
> >> -	if (first_colon && (!first_space || first_colon < first_space))
> >> -		return parse_crashkernel_mem(ck_cmdline, system_ram,
> >> -				crash_size, crash_base);
> >> -	else
> >> +	if (first_colon && (!first_space || first_colon < first_space)) {
> >> +		if (simple_only)
> >> +			return -EINVAL;
> >> +		else
> >> +			return parse_crashkernel_mem(ck_cmdline, system_ram,
> >> +					crash_size, crash_base);
> >> +	} else
> >>  		return parse_crashkernel_simple(ck_cmdline, crash_size,
> >>  				crash_base);
> >
> >Why don't we structure it little differently. Now we seem to have 3 
> >categories of crashkernel= parameters.
> >
> >- crashkernel_simple (crashkernel=X or crashkernel=X@Y)
> >- crashkernel_mem (crashkernel=range:size,.....)
> >- crashkerenl_high_low_suffix (crashkernel=X;high or crashkernel=Y;low)
> >
> >if (suffix) {
> >	parse_crashkernel_high_low_suffix()
> >} else {
> >	if (first_colon.....)
> >		parse_crashkernel_mem()
> >	else
> >		parse_crashkernel_simple();
> >}
> >
> >And now you should not require "simple_only" function parameter and you
> >can also do strict syntax checking for each type of crashkernel=
> >parameter.
> >
> >Thanks
> >Vivek
> 
> -- 
> Sent from my mobile phone. Please excuse brevity and lack of formatting.
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