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

[Dave Young <dyoung@redhat.com>]

On 08/25/16 at 11:00pm, Hari Bathini wrote:
> 
> 
> 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.

Apologize for that, I was not aware it because it is not documented in
kernel-parameters.txt

> 
> > 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! I originally thought fadump will reserve memory in firmware
code, if it is in kernel then it will be better to just extend and reuse
crashkernel=.

Dave
> 
> 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@linux.vnet.ibm.com>
> > > Reviewed-by: Mahesh J Salgaonkar <mahesh@linux.vnet.ibm.com>
> > > ---
> > > 
> > > 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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