Re: [PATCH v3 2/2] powerpc/fadump: parse fadump reserve memory size based on memory range

[Hari Bathini]

On Thursday 25 August 2016 12:31 PM, Dave Young wrote:
> On 08/10/16 at 03:35pm, Hari Bathini wrote:
> > When fadump is enabled, by default 5% of system RAM is reserved for
> > fadump kernel. While that works for most cases, it is not good enough
> > for every case.
> >
> > Currently, to override the default value, fadump supports specifying
> > memory to reserve with fadump_reserve_mem=size, where only a fixed size
> > can be specified. This patch adds support to specify memory size to
> > reserve for different memory ranges as below:
> >
> > 	fadump_reserve_mem=<range1>:<size1>[,<range2>:<size2>,...]
> Hi, Hari

Hi Dave,

> I do not understand why you need introduce the new cmdline param, what's
> the difference between the "fadump reserved" memory and the memory

I am not introducing a new parameter but adding a new syntax for
an existing parameter.

> reserved by "crashkernel="? Can fadump just use crashkernel= to reserve
> memory?

Not all syntaxes supported by crashkernel apply for fadump_reserve_mem.
Nonetheless, it is worth considering reuse of crashkernel parameter instead
of fadump_reserve_mem. Let me see what I can do about this..

Thanks
Hari

> Thanks
> Dave
>
> > Supporting range based input for "fadump_reserve_mem" parameter helps
> > using the same commandline parameter for different system memory sizes.
> >
> > Signed-off-by: Hari Bathini <hbathini@xxxxxxxxxxxxxxxxxx>
> > Reviewed-by: Mahesh J Salgaonkar <mahesh@xxxxxxxxxxxxxxxxxx>
> > ---
> >
> > Changes from v2:
> > 1. Updated changelog
> >
> >
> >   arch/powerpc/kernel/fadump.c |   63 ++++++++++++++++++++++++++++++++++++------
> >   1 file changed, 54 insertions(+), 9 deletions(-)
> >
> > diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
> > index b3a6633..7c01b5b 100644
> > --- a/arch/powerpc/kernel/fadump.c
> > +++ b/arch/powerpc/kernel/fadump.c
> > @@ -193,6 +193,55 @@ static unsigned long init_fadump_mem_struct(struct fadump_mem_struct *fdm,
> >   	return addr;
> >   }
> >   
> > +/*
> > + * This function parses command line for fadump_reserve_mem=
> > + *
> > + * Supports the below two syntaxes:
> > + *    1. fadump_reserve_mem=size
> > + *    2. fadump_reserve_mem=ramsize-range:size[,...]
> > + *
> > + * Sets fw_dump.reserve_bootvar with the memory size
> > + * provided, 0 otherwise
> > + *
> > + * The function returns -EINVAL on failure, 0 otherwise.
> > + */
> > +static int __init parse_fadump_reserve_mem(void)
> > +{
> > +	char *name = "fadump_reserve_mem=";
> > +	char *fadump_cmdline = NULL, *cur;
> > +
> > +	fw_dump.reserve_bootvar = 0;
> > +
> > +	/* find fadump_reserve_mem and use the last one if there are many */
> > +	cur = strstr(boot_command_line, name);
> > +	while (cur) {
> > +		fadump_cmdline = cur;
> > +		cur = strstr(cur+1, name);
> > +	}
> > +
> > +	/* when no fadump_reserve_mem= cmdline option is provided */
> > +	if (!fadump_cmdline)
> > +		return 0;
> > +
> > +	fadump_cmdline += strlen(name);
> > +
> > +	/* for fadump_reserve_mem=size cmdline syntax */
> > +	if (!is_colon_in_param(fadump_cmdline)) {
> > +		fw_dump.reserve_bootvar = memparse(fadump_cmdline, NULL);
> > +		return 0;
> > +	}
> > +
> > +	/* for fadump_reserve_mem=ramsize-range:size[,...] cmdline syntax */
> > +	cur = fadump_cmdline;
> > +	fw_dump.reserve_bootvar = parse_mem_range_size("fadump_reserve_mem",
> > +					&cur, memblock_phys_mem_size());
> > +	if (cur == fadump_cmdline) {
> > +		return -EINVAL;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> >   /**
> >    * fadump_calculate_reserve_size(): reserve variable boot area 5% of System RAM
> >    *
> > @@ -212,12 +261,17 @@ static inline unsigned long fadump_calculate_reserve_size(void)
> >   {
> >   	unsigned long size;
> >   
> > +	/* sets fw_dump.reserve_bootvar */
> > +	parse_fadump_reserve_mem();
> > +
> >   	/*
> >   	 * Check if the size is specified through fadump_reserve_mem= cmdline
> >   	 * option. If yes, then use that.
> >   	 */
> >   	if (fw_dump.reserve_bootvar)
> >   		return fw_dump.reserve_bootvar;
> > +	else
> > +		printk(KERN_INFO "fadump: calculating default boot size\n");
> >   
> >   	/* divide by 20 to get 5% of value */
> >   	size = memblock_end_of_DRAM() / 20;
> > @@ -348,15 +402,6 @@ static int __init early_fadump_param(char *p)
> >   }
> >   early_param("fadump", early_fadump_param);
> >   
> > -/* Look for fadump_reserve_mem= cmdline option */
> > -static int __init early_fadump_reserve_mem(char *p)
> > -{
> > -	if (p)
> > -		fw_dump.reserve_bootvar = memparse(p, &p);
> > -	return 0;
> > -}
> > -early_param("fadump_reserve_mem", early_fadump_reserve_mem);
> > -
> >   static void register_fw_dump(struct fadump_mem_struct *fdm)
> >   {
> >   	int rc;
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