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Commit a6b14fa6 authored by Ashok Raj's avatar Ashok Raj Committed by Tony Luck
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[IA64] Count disabled cpus as potential hot-pluggable CPUs 



Have a facility to account for potentially hot-pluggable CPUs. ACPI doesnt
give a determinstic method to find hot-pluggable CPUs. Hence we use 2 methods
to assist.

- BIOS can mark potentially hot-pluggable CPUs as disabled in the MADT tables.
- User can specify the number of hot-pluggable CPUs via parameter
  additional_cpus=X

The option is enabled only if ACPI_CONFIG_HOTPLUG_CPU=y which enables the
physical hotplug option. Without which user can still use logical onlining
and offlining of CPUs by enabling CONFIG_HOTPLUG_CPU=y

Adds more bits to cpu_possible_map for potentially hot-pluggable cpus.

Signed-off-by: default avatarAshok Raj <ashok.raj@intel.com>
Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
parent 69aa234b

arch/ia64/kernel/acpi.c

+56 −0
Original line number Diff line number Diff line
@@ -761,6 +761,62 @@ int acpi_map_cpu2node(acpi_handle handle, int cpu, long physid) 
	return (0);

}



int additional_cpus __initdata = -1;



static __init int setup_additional_cpus(char *s)

{

	if (s)

		additional_cpus = simple_strtol(s, NULL, 0);



	return 0;

}



early_param("additional_cpus", setup_additional_cpus);



/*

 * cpu_possible_map should be static, it cannot change as cpu's

 * are onlined, or offlined. The reason is per-cpu data-structures

 * are allocated by some modules at init time, and dont expect to

 * do this dynamically on cpu arrival/departure.

 * cpu_present_map on the other hand can change dynamically.

 * In case when cpu_hotplug is not compiled, then we resort to current

 * behaviour, which is cpu_possible == cpu_present.

 * - Ashok Raj

 *

 * Three ways to find out the number of additional hotplug CPUs:

 * - If the BIOS specified disabled CPUs in ACPI/mptables use that.

 * - The user can overwrite it with additional_cpus=NUM

 * - Otherwise don't reserve additional CPUs.

 */

__init void prefill_possible_map(void)

{

	int i;

	int possible, disabled_cpus;



	disabled_cpus = total_cpus - available_cpus;

 	if (additional_cpus == -1) {

 		if (disabled_cpus > 0) {

 			possible = total_cpus;

			additional_cpus = disabled_cpus;

		}

 		else {

			possible = available_cpus;

			additional_cpus = 0;

		}

 	} else {

		possible = available_cpus + additional_cpus;

	}

	if (possible > NR_CPUS)

		possible = NR_CPUS;



	printk(KERN_INFO "SMP: Allowing %d CPUs, %d hotplug CPUs\n",

		possible,

	        max_t(int, additional_cpus, 0));



	for (i = 0; i < possible; i++)

		cpu_set(i, cpu_possible_map);

}



int acpi_map_lsapic(acpi_handle handle, int *pcpu)

{

	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };

arch/ia64/kernel/setup.c

+4 −0
Original line number Diff line number Diff line
@@ -430,6 +430,7 @@ setup_arch (char **cmdline_p) 
	if (early_console_setup(*cmdline_p) == 0)

		mark_bsp_online();



	parse_early_param();

#ifdef CONFIG_ACPI

	/* Initialize the ACPI boot-time table parser */

	acpi_table_init();
@@ -688,6 +689,9 @@ void 
setup_per_cpu_areas (void)

{

	/* start_kernel() requires this... */

#ifdef CONFIG_ACPI_HOTPLUG_CPU

	prefill_possible_map();

#endif

}



/*

include/asm-ia64/acpi.h

+2 −0
Original line number Diff line number Diff line
@@ -106,6 +106,8 @@ extern unsigned int can_cpei_retarget(void); 
extern unsigned int is_cpu_cpei_target(unsigned int cpu);

extern void set_cpei_target_cpu(unsigned int cpu);

extern unsigned int get_cpei_target_cpu(void);

extern void prefill_possible_map(void);

extern int additional_cpus;



#ifdef CONFIG_ACPI_NUMA

/* Proximity bitmap length; _PXM is at most 255 (8 bit)*/