Re: [v2,1/2] powerpc/xmon: Paged output for paca display

[Sam Bobroff <sam.bobroff@au1.ibm.com>]

On Tue, Oct 06, 2015 at 10:05:38PM +1100, Michael Ellerman wrote:
> On Fri, 2015-21-08 at 04:24:27 UTC, Sam bobroff wrote:
> > The paca display is already more than 24 lines, which can be problematic
> > if you have an old school 80x24 terminal, or more likely you are on a
> > virtual terminal which does not scroll for whatever reason.
> > 
> > This patch adds a new command ".", which takes a single (hex) numeric
> > argument: lines per page. It will cause the output of "dp" and "dpa"
> > to be broken into pages, if necessary.
> > 
> > This is implemented by running over the entire output both for the
> > initial command and for each subsequent page: the visible part is
> > clipped out by checking line numbers. This is a simplistic approach
> > but minimally invasive; it is intended to be easily reusable for other
> > commands.
> > 
> > Sample output:
> > 
> > 0:mon> .10
> > 0:mon> dp1
> > paca for cpu 0x1 @ c00000000fdc0480:
> >  possible         = yes
> >  present          = yes
> >  online           = yes
> >  lock_token       = 0x8000            	(0x8)
> >  paca_index       = 0x1               	(0xa)
> >  kernel_toc       = 0xc000000000eb2400	(0x10)
> >  kernelbase       = 0xc000000000000000	(0x18)
> >  kernel_msr       = 0xb000000000001032	(0x20)
> >  emergency_sp     = 0xc00000003ffe8000	(0x28)
> >  mc_emergency_sp  = 0xc00000003ffe4000	(0x2e0)
> >  in_mce           = 0x0               	(0x2e8)
> >  data_offset      = 0x7f170000        	(0x30)
> >  hw_cpu_id        = 0x8               	(0x38)
> >  cpu_start        = 0x1               	(0x3a)
> >  kexec_state      = 0x0               	(0x3b)
> > [Enter for next page]
> > 0:mon>
> >  __current        = 0xc00000007e696620	(0x290)
> >  kstack           = 0xc00000007e6ebe30	(0x298)
> >  stab_rr          = 0xb               	(0x2a0)
> >  saved_r1         = 0xc00000007ef37860	(0x2a8)
> >  trap_save        = 0x0               	(0x2b8)
> >  soft_enabled     = 0x0               	(0x2ba)
> >  irq_happened     = 0x1               	(0x2bb)
> >  io_sync          = 0x0               	(0x2bc)
> >  irq_work_pending = 0x0               	(0x2bd)
> >  nap_state_lost   = 0x0               	(0x2be)
> > 0:mon>
> > 
> > (Based on a similar patch by Michael Ellerman <mpe@ellerman.id.au>
> > "[v2] powerpc/xmon: Allow limiting the size of the paca display".
> > This patch is an alternative and cannot coexist with the original.)
> > 
> > Signed-off-by: Sam Bobroff <sam.bobroff@au1.ibm.com>
> > ---
> >  arch/powerpc/xmon/xmon.c | 86 +++++++++++++++++++++++++++++++++++++++---------
> >  1 file changed, 71 insertions(+), 15 deletions(-)
> > 
> > diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
> > index e599259..9ce9e7d 100644
> > --- a/arch/powerpc/xmon/xmon.c
> > +++ b/arch/powerpc/xmon/xmon.c
> > @@ -72,6 +72,12 @@ static int xmon_gate;
> >  
> >  static unsigned long in_xmon __read_mostly = 0;
> >  
> > +#define XMON_PRINTF(...) do { if (paged_vis()) printf(__VA_ARGS__); } while (0)
> 
> Can you do this is a proper function. I know it will need to be varargs, but
> that shouldn't be too ugly.

Sure, but I think I'll re-work the core of the logic and place it directly into
nonstdio.c. That will allow me to implement it directly in xmon_write() and
there won't need to be any change here at all. It will also allow blocking
during the output which will remove the whole 'run the command several times
and print a slice of it' system.

I'll post a v3.

> 
> > +#define MAX_PAGED_SIZE 1024
> 
> Why do we need a max at all?

OK, removed.

> > +static unsigned long paged_size = 0, paged_pos, paged_cur_page;
> 
> > +#ifdef CONFIG_PPC64
> > +static unsigned long paca_cpu;
> > +#endif
> 
> That can just be static in dump_pacas() by the looks.

This won't be needed in the new version.

> >  static unsigned long adrs;
> >  static int size = 1;
> >  #define MAX_DUMP (128 * 1024)
> > @@ -242,6 +248,9 @@ Commands:\n\
> >  "  u	dump TLB\n"
> >  #endif
> >  "  ?	help\n"
> > +#ifdef CONFIG_PPC64
> > +"  .#	limit output to # lines per page (dump paca only)\n"
> > +#endif
> 
> Don't make it 64-bit only.

It's only because the paca display itself is 64 bit only.

> >  "  zr	reboot\n\
> >    zh	halt\n"
> >  ;
> > @@ -833,6 +842,19 @@ static void remove_cpu_bpts(void)
> >  	write_ciabr(0);
> >  }
> >  
> > +static void paged_set_size(void)
> 
> "paged" isn't reading very well for me. Can we use "pagination" instead? I know
> it's longer but monitors are wide these days.
> 
> Also I prefer verb first usually, so set_pagination_size() etc.

Sure thing.

> > +{
> > +	if (!scanhex(&paged_size) || (paged_size > MAX_PAGED_SIZE)) {
> > +		printf("Invalid number of lines per page (max: %d).\n",
> > +		       MAX_PAGED_SIZE);
> > +		paged_size = 0;
> > +	}
> > +}
> > +static void paged_reset(void)
> > +{
> > +	paged_cur_page = 0;
> > +}
> 
> You only call that once so a function seems like over kill.

Not needed in next version.

> >  /* Command interpreting routine */
> >  static char *last_cmd;
> >  
> > @@ -863,7 +885,8 @@ cmds(struct pt_regs *excp)
> >  			take_input(last_cmd);
> >  			last_cmd = NULL;
> >  			cmd = inchar();
> > -		}
> > +		} else
> > +			paged_reset();
> >  		switch (cmd) {
> >  		case 'm':
> >  			cmd = inchar();
> > @@ -924,6 +947,9 @@ cmds(struct pt_regs *excp)
> >  		case '?':
> >  			xmon_puts(help_string);
> >  			break;
> > +		case '.':
> > +			paged_set_size();
> > +			break;
> >  		case 'b':
> >  			bpt_cmds();
> >  			break;
> > @@ -2069,6 +2095,31 @@ static void xmon_rawdump (unsigned long adrs, long ndump)
> >  	printf("\n");
> >  }
> >  
> > +static void paged_start(void)
> > +{
> > +	paged_pos = 0;
> > +}
> > +
> > +static void paged_end(char *next_cmd)
> > +{
> > +	unsigned long next_page_start = ++paged_cur_page * paged_size;
> > +
> > +	if (paged_size && (paged_pos > next_page_start)) {
> > +		last_cmd = next_cmd;
> > +		printf("[Enter for next page]\n");
> > +	}
> > +}
> > +
> > +static bool paged_vis(void)
> > +{
> > +	bool rv = (!paged_size
> > +	|| ((paged_pos >= (paged_size * paged_cur_page))
> > +	&& (paged_pos < (paged_size * (paged_cur_page + 1)))));
> 
> Erm.

Not needed in next version :-)

> > +
> > +	paged_pos++;
> > +	return rv;
> > +}
> > +
> >  #ifdef CONFIG_PPC64
> >  static void dump_one_paca(int cpu)
> >  {
> > @@ -2084,15 +2135,17 @@ static void dump_one_paca(int cpu)
> >  
> >  	p = &paca[cpu];
> >  
> > -	printf("paca for cpu 0x%x @ %p:\n", cpu, p);
> > +	XMON_PRINTF("paca for cpu 0x%x @ %p:\n", cpu, p);
> >  
> > -	printf(" %-*s = %s\n", 16, "possible", cpu_possible(cpu) ? "yes" : "no");
> > -	printf(" %-*s = %s\n", 16, "present", cpu_present(cpu) ? "yes" : "no");
> > -	printf(" %-*s = %s\n", 16, "online", cpu_online(cpu) ? "yes" : "no");
> > +	XMON_PRINTF(" %-*s = %s\n", 16, "possible", cpu_possible(cpu) ? "yes" : "no");
> > +	XMON_PRINTF(" %-*s = %s\n", 16, "present", cpu_present(cpu) ? "yes" : "no");
> > +	XMON_PRINTF(" %-*s = %s\n", 16, "online", cpu_online(cpu) ? "yes" : "no");
> >  
> > -#define DUMP(paca, name, format) \
> > -	printf(" %-*s = %#-*"format"\t(0x%lx)\n", 16, #name, 18, paca->name, \
> > -		offsetof(struct paca_struct, name));
> > +#define DUMP(paca, name, format) do { \
> > +		if (paged_vis()) \
> > +			printf(" %-*s = %#-*"format"\t(0x%lx)\n", 16, #name, 18, \
> > +			       paca->name, offsetof(struct paca_struct, name)); \
> > +} while (0)
> >  
> >  	DUMP(p, lock_token, "x");
> >  	DUMP(p, paca_index, "x");
> > @@ -2134,13 +2187,14 @@ static void dump_all_pacas(void)
> >  		return;
> >  	}
> >  
> > +	paged_start();
> >  	for_each_possible_cpu(cpu)
> >  		dump_one_paca(cpu);
> > +	paged_end("dpa\n");
> >  }
> >  
> >  static void dump_pacas(void)
> >  {
> > -	unsigned long num;
> >  	int c;
> >  
> >  	c = inchar();
> > @@ -2148,13 +2202,15 @@ static void dump_pacas(void)
> >  		dump_all_pacas();
> >  		return;
> >  	}
> > +	if (c != '_') {
> 
> What's that about?

It was to do with re-running the command for the next page, but it's not needed
in the next version.

> > +		termch = c;
> > +		if (!scanhex(&paca_cpu))
> > +			paca_cpu = xmon_owner;
> > +	}
> >  
> > -	termch = c;	/* Put c back, it wasn't 'a' */
> > -
> > -	if (scanhex(&num))
> > -		dump_one_paca(num);
> > -	else
> > -		dump_one_paca(xmon_owner);
> > +	paged_start();
> > +	dump_one_paca(paca_cpu);
> > +	paged_end("dp_\n");
> >  }
> >  #endif
> 
> cheers

Thanks for the review,
Sam.