[mirror_ubuntu-eoan-kernel.git] / arch / powerpc / platforms / powernv / subcore.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright 2013, Michael (Ellerman|Neuling), IBM Corporation.
 */

#define pr_fmt(fmt)	"powernv: " fmt

#include <linux/kernel.h>
#include <linux/cpu.h>
#include <linux/cpumask.h>
#include <linux/device.h>
#include <linux/gfp.h>
#include <linux/smp.h>
#include <linux/stop_machine.h>

#include <asm/cputhreads.h>
#include <asm/cpuidle.h>
#include <asm/kvm_ppc.h>
#include <asm/machdep.h>
#include <asm/opal.h>
#include <asm/smp.h>

#include "subcore.h"
#include "powernv.h"


/*
 * Split/unsplit procedure:
 *
 * A core can be in one of three states, unsplit, 2-way split, and 4-way split.
 *
 * The mapping to subcores_per_core is simple:
 *
 *  State       | subcores_per_core
 *  ------------|------------------
 *  Unsplit     |        1
 *  2-way split |        2
 *  4-way split |        4
 *
 * The core is split along thread boundaries, the mapping between subcores and
 * threads is as follows:
 *
 *  Unsplit:
 *          ----------------------------
 *  Subcore |            0             |
 *          ----------------------------
 *  Thread  |  0  1  2  3  4  5  6  7  |
 *          ----------------------------
 *
 *  2-way split:
 *          -------------------------------------
 *  Subcore |        0        |        1        |
 *          -------------------------------------
 *  Thread  |  0   1   2   3  |  4   5   6   7  |
 *          -------------------------------------
 *
 *  4-way split:
 *          -----------------------------------------
 *  Subcore |    0    |    1    |    2    |    3    |
 *          -----------------------------------------
 *  Thread  |  0   1  |  2   3  |  4   5  |  6   7  |
 *          -----------------------------------------
 *
 *
 * Transitions
 * -----------
 *
 * It is not possible to transition between either of the split states, the
 * core must first be unsplit. The legal transitions are:
 *
 *  -----------          ---------------
 *  |         |  <---->  | 2-way split |
 *  |         |          ---------------
 *  | Unsplit |
 *  |         |          ---------------
 *  |         |  <---->  | 4-way split |
 *  -----------          ---------------
 *
 * Unsplitting
 * -----------
 *
 * Unsplitting is the simpler procedure. It requires thread 0 to request the
 * unsplit while all other threads NAP.
 *
 * Thread 0 clears HID0_POWER8_DYNLPARDIS (Dynamic LPAR Disable). This tells
 * the hardware that if all threads except 0 are napping, the hardware should
 * unsplit the core.
 *
 * Non-zero threads are sent to a NAP loop, they don't exit the loop until they
 * see the core unsplit.
 *
 * Core 0 spins waiting for the hardware to see all the other threads napping
 * and perform the unsplit.
 *
 * Once thread 0 sees the unsplit, it IPIs the secondary threads to wake them
 * out of NAP. They will then see the core unsplit and exit the NAP loop.
 *
 * Splitting
 * ---------
 *
 * The basic splitting procedure is fairly straight forward. However it is
 * complicated by the fact that after the split occurs, the newly created
 * subcores are not in a fully initialised state.
 *
 * Most notably the subcores do not have the correct value for SDR1, which
 * means they must not be running in virtual mode when the split occurs. The
 * subcores have separate timebases SPRs but these are pre-synchronised by
 * opal.
 *
 * To begin with secondary threads are sent to an assembly routine. There they
 * switch to real mode, so they are immune to the uninitialised SDR1 value.
 * Once in real mode they indicate that they are in real mode, and spin waiting
 * to see the core split.
 *
 * Thread 0 waits to see that all secondaries are in real mode, and then begins
 * the splitting procedure. It firstly sets HID0_POWER8_DYNLPARDIS, which
 * prevents the hardware from unsplitting. Then it sets the appropriate HID bit
 * to request the split, and spins waiting to see that the split has happened.
 *
 * Concurrently the secondaries will notice the split. When they do they set up
 * their SPRs, notably SDR1, and then they can return to virtual mode and exit
 * the procedure.
 */

/* Initialised at boot by subcore_init() */
static int subcores_per_core;

/*
 * Used to communicate to offline cpus that we want them to pop out of the
 * offline loop and do a split or unsplit.
 *
 * 0 - no split happening
 * 1 - unsplit in progress
 * 2 - split to 2 in progress
 * 4 - split to 4 in progress
 */
static int new_split_mode;

static cpumask_var_t cpu_offline_mask;

struct split_state {
	u8 step;
	u8 master;
};

static DEFINE_PER_CPU(struct split_state, split_state);

static void wait_for_sync_step(int step)
{
	int i, cpu = smp_processor_id();

	for (i = cpu + 1; i < cpu + threads_per_core; i++)
		while(per_cpu(split_state, i).step < step)
			barrier();

	/* Order the wait loop vs any subsequent loads/stores. */
	mb();
}

static void update_hid_in_slw(u64 hid0)
{
	u64 idle_states = pnv_get_supported_cpuidle_states();

	if (idle_states & OPAL_PM_WINKLE_ENABLED) {
		/* OPAL call to patch slw with the new HID0 value */
		u64 cpu_pir = hard_smp_processor_id();

		opal_slw_set_reg(cpu_pir, SPRN_HID0, hid0);
	}
}

static void unsplit_core(void)
{
	u64 hid0, mask;
	int i, cpu;

	mask = HID0_POWER8_2LPARMODE | HID0_POWER8_4LPARMODE;

	cpu = smp_processor_id();
	if (cpu_thread_in_core(cpu) != 0) {
		while (mfspr(SPRN_HID0) & mask)
			power7_idle_type(PNV_THREAD_NAP);

		per_cpu(split_state, cpu).step = SYNC_STEP_UNSPLIT;
		return;
	}

	hid0 = mfspr(SPRN_HID0);
	hid0 &= ~HID0_POWER8_DYNLPARDIS;
	update_power8_hid0(hid0);
	update_hid_in_slw(hid0);

	while (mfspr(SPRN_HID0) & mask)
		cpu_relax();

	/* Wake secondaries out of NAP */
	for (i = cpu + 1; i < cpu + threads_per_core; i++)
		smp_send_reschedule(i);

	wait_for_sync_step(SYNC_STEP_UNSPLIT);
}

static void split_core(int new_mode)
{
	struct {  u64 value; u64 mask; } split_parms[2] = {
		{ HID0_POWER8_1TO2LPAR, HID0_POWER8_2LPARMODE },
		{ HID0_POWER8_1TO4LPAR, HID0_POWER8_4LPARMODE }
	};
	int i, cpu;
	u64 hid0;

	/* Convert new_mode (2 or 4) into an index into our parms array */
	i = (new_mode >> 1) - 1;
	BUG_ON(i < 0 || i > 1);

	cpu = smp_processor_id();
	if (cpu_thread_in_core(cpu) != 0) {
		split_core_secondary_loop(&per_cpu(split_state, cpu).step);
		return;
	}

	wait_for_sync_step(SYNC_STEP_REAL_MODE);

	/* Write new mode */
	hid0  = mfspr(SPRN_HID0);
	hid0 |= HID0_POWER8_DYNLPARDIS | split_parms[i].value;
	update_power8_hid0(hid0);
	update_hid_in_slw(hid0);

	/* Wait for it to happen */
	while (!(mfspr(SPRN_HID0) & split_parms[i].mask))
		cpu_relax();
}

static void cpu_do_split(int new_mode)
{
	/*
	 * At boot subcores_per_core will be 0, so we will always unsplit at
	 * boot. In the usual case where the core is already unsplit it's a
	 * nop, and this just ensures the kernel's notion of the mode is
	 * consistent with the hardware.
	 */
	if (subcores_per_core != 1)
		unsplit_core();

	if (new_mode != 1)
		split_core(new_mode);

	mb();
	per_cpu(split_state, smp_processor_id()).step = SYNC_STEP_FINISHED;
}

bool cpu_core_split_required(void)
{
	smp_rmb();

	if (!new_split_mode)
		return false;

	cpu_do_split(new_split_mode);

	return true;
}

void update_subcore_sibling_mask(void)
{
	int cpu;
	/*
	 * sibling mask for the first cpu. Left shift this by required bits
	 * to get sibling mask for the rest of the cpus.
	 */
	int sibling_mask_first_cpu =  (1 << threads_per_subcore) - 1;

	for_each_possible_cpu(cpu) {
		int tid = cpu_thread_in_core(cpu);
		int offset = (tid / threads_per_subcore) * threads_per_subcore;
		int mask = sibling_mask_first_cpu << offset;

		paca_ptrs[cpu]->subcore_sibling_mask = mask;

	}
}

static int cpu_update_split_mode(void *data)
{
	int cpu, new_mode = *(int *)data;

	if (this_cpu_ptr(&split_state)->master) {
		new_split_mode = new_mode;
		smp_wmb();

		cpumask_andnot(cpu_offline_mask, cpu_present_mask,
			       cpu_online_mask);

		/* This should work even though the cpu is offline */
		for_each_cpu(cpu, cpu_offline_mask)
			smp_send_reschedule(cpu);
	}

	cpu_do_split(new_mode);

	if (this_cpu_ptr(&split_state)->master) {
		/* Wait for all cpus to finish before we touch subcores_per_core */
		for_each_present_cpu(cpu) {
			if (cpu >= setup_max_cpus)
				break;

			while(per_cpu(split_state, cpu).step < SYNC_STEP_FINISHED)
				barrier();
		}

		new_split_mode = 0;

		/* Make the new mode public */
		subcores_per_core = new_mode;
		threads_per_subcore = threads_per_core / subcores_per_core;
		update_subcore_sibling_mask();

		/* Make sure the new mode is written before we exit */
		mb();
	}

	return 0;
}

static int set_subcores_per_core(int new_mode)
{
	struct split_state *state;
	int cpu;

	if (kvm_hv_mode_active()) {
		pr_err("Unable to change split core mode while KVM active.\n");
		return -EBUSY;
	}

	/*
	 * We are only called at boot, or from the sysfs write. If that ever
	 * changes we'll need a lock here.
	 */
	BUG_ON(new_mode < 1 || new_mode > 4 || new_mode == 3);

	for_each_present_cpu(cpu) {
		state = &per_cpu(split_state, cpu);
		state->step = SYNC_STEP_INITIAL;
		state->master = 0;
	}

	cpus_read_lock();

	/* This cpu will update the globals before exiting stop machine */
	this_cpu_ptr(&split_state)->master = 1;

	/* Ensure state is consistent before we call the other cpus */
	mb();

	stop_machine_cpuslocked(cpu_update_split_mode, &new_mode,
				cpu_online_mask);

	cpus_read_unlock();

	return 0;
}

static ssize_t __used store_subcores_per_core(struct device *dev,
		struct device_attribute *attr, const char *buf,
		size_t count)
{
	unsigned long val;
	int rc;

	/* We are serialised by the attribute lock */

	rc = sscanf(buf, "%lx", &val);
	if (rc != 1)
		return -EINVAL;

	switch (val) {
	case 1:
	case 2:
	case 4:
		if (subcores_per_core == val)
			/* Nothing to do */
			goto out;
		break;
	default:
		return -EINVAL;
	}

	rc = set_subcores_per_core(val);
	if (rc)
		return rc;

out:
	return count;
}

static ssize_t show_subcores_per_core(struct device *dev,
		struct device_attribute *attr, char *buf)
{
	return sprintf(buf, "%x\n", subcores_per_core);
}

static DEVICE_ATTR(subcores_per_core, 0644,
		show_subcores_per_core, store_subcores_per_core);

static int subcore_init(void)
{
	unsigned pvr_ver;

	pvr_ver = PVR_VER(mfspr(SPRN_PVR));

	if (pvr_ver != PVR_POWER8 &&
	    pvr_ver != PVR_POWER8E &&
	    pvr_ver != PVR_POWER8NVL)
		return 0;

	/*
	 * We need all threads in a core to be present to split/unsplit so
         * continue only if max_cpus are aligned to threads_per_core.
	 */
	if (setup_max_cpus % threads_per_core)
		return 0;

	BUG_ON(!alloc_cpumask_var(&cpu_offline_mask, GFP_KERNEL));

	set_subcores_per_core(1);

	return device_create_file(cpu_subsys.dev_root,
				  &dev_attr_subcores_per_core);
}
machine_device_initcall(powernv, subcore_init);
Commit	Line	Data
2874c5fd	1	// SPDX-License-Identifier: GPL-2.0-or-later
e2186023 ME	2	/*
e2186023 ME	3	* Copyright 2013, Michael (Ellerman\|Neuling), IBM Corporation.
e2186023 ME	4	*/
	5
	6	#define pr_fmt(fmt) "powernv: " fmt
	7
	8	#include <linux/kernel.h>
	9	#include <linux/cpu.h>
	10	#include <linux/cpumask.h>
	11	#include <linux/device.h>
	12	#include <linux/gfp.h>
	13	#include <linux/smp.h>
	14	#include <linux/stop_machine.h>
	15
	16	#include <asm/cputhreads.h>
2201f994	17	#include <asm/cpuidle.h>
e2186023 ME	18	#include <asm/kvm_ppc.h>
	19	#include <asm/machdep.h>
	20	#include <asm/opal.h>
	21	#include <asm/smp.h>
	22
	23	#include "subcore.h"
1217d34b	24	#include "powernv.h"
e2186023 ME	25
	26
	27	/*
	28	* Split/unsplit procedure:
	29	*
	30	* A core can be in one of three states, unsplit, 2-way split, and 4-way split.
	31	*
	32	* The mapping to subcores_per_core is simple:
	33	*
	34	* State \| subcores_per_core
	35	* ------------\|------------------
	36	* Unsplit \| 1
	37	* 2-way split \| 2
	38	* 4-way split \| 4
	39	*
	40	* The core is split along thread boundaries, the mapping between subcores and
	41	* threads is as follows:
	42	*
	43	* Unsplit:
	44	* ----------------------------
	45	* Subcore \| 0 \|
	46	* ----------------------------
	47	* Thread \| 0 1 2 3 4 5 6 7 \|
	48	* ----------------------------
	49	*
	50	* 2-way split:
	51	* -------------------------------------
	52	* Subcore \| 0 \| 1 \|
	53	* -------------------------------------
	54	* Thread \| 0 1 2 3 \| 4 5 6 7 \|
	55	* -------------------------------------
	56	*
	57	* 4-way split:
	58	* -----------------------------------------
	59	* Subcore \| 0 \| 1 \| 2 \| 3 \|
	60	* -----------------------------------------
	61	* Thread \| 0 1 \| 2 3 \| 4 5 \| 6 7 \|
	62	* -----------------------------------------
	63	*
	64	*
	65	* Transitions
	66	* -----------
	67	*
	68	* It is not possible to transition between either of the split states, the
	69	* core must first be unsplit. The legal transitions are:
	70	*
	71	* ----------- ---------------
	72	* \| \| <----> \| 2-way split \|
	73	* \| \| ---------------
	74	* \| Unsplit \|
	75	* \| \| ---------------
	76	* \| \| <----> \| 4-way split \|
	77	* ----------- ---------------
	78	*
	79	* Unsplitting
	80	* -----------
	81	*
	82	* Unsplitting is the simpler procedure. It requires thread 0 to request the
	83	* unsplit while all other threads NAP.
	84	*
	85	* Thread 0 clears HID0_POWER8_DYNLPARDIS (Dynamic LPAR Disable). This tells
	86	* the hardware that if all threads except 0 are napping, the hardware should
	87	* unsplit the core.
	88	*
89	* Non-zero threads are sent to a NAP loop, they don't exit the loop until they
90	* see the core unsplit.
91	*
92	* Core 0 spins waiting for the hardware to see all the other threads napping
93	* and perform the unsplit.
94	*
95	* Once thread 0 sees the unsplit, it IPIs the secondary threads to wake them
96	* out of NAP. They will then see the core unsplit and exit the NAP loop.
97	*
98	* Splitting
99	* ---------
100	*
101	* The basic splitting procedure is fairly straight forward. However it is
102	* complicated by the fact that after the split occurs, the newly created
103	* subcores are not in a fully initialised state.
104	*
105	* Most notably the subcores do not have the correct value for SDR1, which
106	* means they must not be running in virtual mode when the split occurs. The
107	* subcores have separate timebases SPRs but these are pre-synchronised by
108	* opal.
109	*
110	* To begin with secondary threads are sent to an assembly routine. There they
111	* switch to real mode, so they are immune to the uninitialised SDR1 value.
112	* Once in real mode they indicate that they are in real mode, and spin waiting
113	* to see the core split.
114	*
115	* Thread 0 waits to see that all secondaries are in real mode, and then begins
116	* the splitting procedure. It firstly sets HID0_POWER8_DYNLPARDIS, which
117	* prevents the hardware from unsplitting. Then it sets the appropriate HID bit
118	* to request the split, and spins waiting to see that the split has happened.
119	*
120	* Concurrently the secondaries will notice the split. When they do they set up
121	* their SPRs, notably SDR1, and then they can return to virtual mode and exit
122	* the procedure.
123	*/
124
125	/* Initialised at boot by subcore_init() */
126	static int subcores_per_core;
127
128	/*
129	* Used to communicate to offline cpus that we want them to pop out of the
130	* offline loop and do a split or unsplit.
131	*
132	* 0 - no split happening
133	* 1 - unsplit in progress
134	* 2 - split to 2 in progress
135	* 4 - split to 4 in progress
136	*/
137	static int new_split_mode;
138
139	static cpumask_var_t cpu_offline_mask;
140
141	struct split_state {
142	u8 step;
143	u8 master;
144	};
145
146	static DEFINE_PER_CPU(struct split_state, split_state);
147
148	static void wait_for_sync_step(int step)
149	{
150	int i, cpu = smp_processor_id();
151
152	for (i = cpu + 1; i < cpu + threads_per_core; i++)
153	while(per_cpu(split_state, i).step < step)
154	barrier();
155
156	/* Order the wait loop vs any subsequent loads/stores. */
157	mb();
158	}
159
77b54e9f SP	160	static void update_hid_in_slw(u64 hid0)
	161	{
	162	u64 idle_states = pnv_get_supported_cpuidle_states();
	163
	164	if (idle_states & OPAL_PM_WINKLE_ENABLED) {
	165	/* OPAL call to patch slw with the new HID0 value */
	166	u64 cpu_pir = hard_smp_processor_id();
	167
	168	opal_slw_set_reg(cpu_pir, SPRN_HID0, hid0);
	169	}
	170	}
	171
e2186023 ME	172	static void unsplit_core(void)
	173	{
	174	u64 hid0, mask;
	175	int i, cpu;
	176
	177	mask = HID0_POWER8_2LPARMODE \| HID0_POWER8_4LPARMODE;
	178
	179	cpu = smp_processor_id();
	180	if (cpu_thread_in_core(cpu) != 0) {
	181	while (mfspr(SPRN_HID0) & mask)
10d91611	182	power7_idle_type(PNV_THREAD_NAP);
e2186023 ME	183
	184	per_cpu(split_state, cpu).step = SYNC_STEP_UNSPLIT;
	185	return;
	186	}
	187
	188	hid0 = mfspr(SPRN_HID0);
	189	hid0 &= ~HID0_POWER8_DYNLPARDIS;
e63dbd16	190	update_power8_hid0(hid0);
77b54e9f	191	update_hid_in_slw(hid0);
e2186023 ME	192
	193	while (mfspr(SPRN_HID0) & mask)
	194	cpu_relax();
	195
	196	/* Wake secondaries out of NAP */
	197	for (i = cpu + 1; i < cpu + threads_per_core; i++)
	198	smp_send_reschedule(i);
	199
	200	wait_for_sync_step(SYNC_STEP_UNSPLIT);
	201	}
	202
	203	static void split_core(int new_mode)
	204	{
	205	struct { u64 value; u64 mask; } split_parms[2] = {
	206	{ HID0_POWER8_1TO2LPAR, HID0_POWER8_2LPARMODE },
	207	{ HID0_POWER8_1TO4LPAR, HID0_POWER8_4LPARMODE }
	208	};
	209	int i, cpu;
	210	u64 hid0;
	211
	212	/* Convert new_mode (2 or 4) into an index into our parms array */
	213	i = (new_mode >> 1) - 1;
	214	BUG_ON(i < 0 \|\| i > 1);
	215
	216	cpu = smp_processor_id();
	217	if (cpu_thread_in_core(cpu) != 0) {
	218	split_core_secondary_loop(&per_cpu(split_state, cpu).step);
	219	return;
	220	}
	221
	222	wait_for_sync_step(SYNC_STEP_REAL_MODE);
	223
	224	/* Write new mode */
	225	hid0 = mfspr(SPRN_HID0);
	226	hid0 \|= HID0_POWER8_DYNLPARDIS \| split_parms[i].value;
e63dbd16	227	update_power8_hid0(hid0);
77b54e9f	228	update_hid_in_slw(hid0);
e2186023 ME	229
	230	/* Wait for it to happen */
	231	while (!(mfspr(SPRN_HID0) & split_parms[i].mask))
	232	cpu_relax();
	233	}
	234
	235	static void cpu_do_split(int new_mode)
	236	{
	237	/*
	238	* At boot subcores_per_core will be 0, so we will always unsplit at
	239	* boot. In the usual case where the core is already unsplit it's a
	240	* nop, and this just ensures the kernel's notion of the mode is
	241	* consistent with the hardware.
	242	*/
	243	if (subcores_per_core != 1)
	244	unsplit_core();
	245
	246	if (new_mode != 1)
	247	split_core(new_mode);
	248
	249	mb();
	250	per_cpu(split_state, smp_processor_id()).step = SYNC_STEP_FINISHED;
	251	}
	252
	253	bool cpu_core_split_required(void)
	254	{
	255	smp_rmb();
	256
	257	if (!new_split_mode)
	258	return false;
	259
	260	cpu_do_split(new_split_mode);
	261
	262	return true;
	263	}
	264
77b54e9f SP	265	void update_subcore_sibling_mask(void)
	266	{
	267	int cpu;
	268	/*
	269	* sibling mask for the first cpu. Left shift this by required bits
	270	* to get sibling mask for the rest of the cpus.
	271	*/
	272	int sibling_mask_first_cpu = (1 << threads_per_subcore) - 1;
	273
	274	for_each_possible_cpu(cpu) {
	275	int tid = cpu_thread_in_core(cpu);
	276	int offset = (tid / threads_per_subcore) * threads_per_subcore;
	277	int mask = sibling_mask_first_cpu << offset;
	278
d2e60075	279	paca_ptrs[cpu]->subcore_sibling_mask = mask;
77b54e9f SP	280
	281	}
	282	}
	283
e2186023 ME	284	static int cpu_update_split_mode(void *data)
	285	{
	286	int cpu, new_mode = (int )data;
	287
	288	if (this_cpu_ptr(&split_state)->master) {
	289	new_split_mode = new_mode;
	290	smp_wmb();
	291
	292	cpumask_andnot(cpu_offline_mask, cpu_present_mask,
	293	cpu_online_mask);
	294
	295	/* This should work even though the cpu is offline */
	296	for_each_cpu(cpu, cpu_offline_mask)
	297	smp_send_reschedule(cpu);
	298	}
	299
	300	cpu_do_split(new_mode);
	301
	302	if (this_cpu_ptr(&split_state)->master) {
	303	/* Wait for all cpus to finish before we touch subcores_per_core */
	304	for_each_present_cpu(cpu) {
	305	if (cpu >= setup_max_cpus)
	306	break;
	307
	308	while(per_cpu(split_state, cpu).step < SYNC_STEP_FINISHED)
	309	barrier();
	310	}
	311
	312	new_split_mode = 0;
	313
	314	/* Make the new mode public */
	315	subcores_per_core = new_mode;
	316	threads_per_subcore = threads_per_core / subcores_per_core;
77b54e9f	317	update_subcore_sibling_mask();
e2186023 ME	318
	319	/* Make sure the new mode is written before we exit */
	320	mb();
	321	}
	322
	323	return 0;
	324	}
	325
	326	static int set_subcores_per_core(int new_mode)
	327	{
	328	struct split_state *state;
	329	int cpu;
	330
	331	if (kvm_hv_mode_active()) {
	332	pr_err("Unable to change split core mode while KVM active.\n");
	333	return -EBUSY;
	334	}
	335
	336	/*
	337	* We are only called at boot, or from the sysfs write. If that ever
	338	* changes we'll need a lock here.
	339	*/
	340	BUG_ON(new_mode < 1 \|\| new_mode > 4 \|\| new_mode == 3);
	341
	342	for_each_present_cpu(cpu) {
	343	state = &per_cpu(split_state, cpu);
	344	state->step = SYNC_STEP_INITIAL;
	345	state->master = 0;
	346	}
	347
f9a69931	348	cpus_read_lock();
e2186023 ME	349
	350	/* This cpu will update the globals before exiting stop machine */
	351	this_cpu_ptr(&split_state)->master = 1;
	352
	353	/* Ensure state is consistent before we call the other cpus */
	354	mb();
	355
f9a69931 SAS	356	stop_machine_cpuslocked(cpu_update_split_mode, &new_mode,
f9a69931 SAS	357	cpu_online_mask);
e2186023	358
f9a69931	359	cpus_read_unlock();
e2186023 ME	360
	361	return 0;
	362	}
	363
	364	static ssize_t __used store_subcores_per_core(struct device *dev,
	365	struct device_attribute attr, const char buf,
	366	size_t count)
	367	{
	368	unsigned long val;
	369	int rc;
	370
	371	/* We are serialised by the attribute lock */
	372
	373	rc = sscanf(buf, "%lx", &val);
	374	if (rc != 1)
	375	return -EINVAL;
	376
	377	switch (val) {
	378	case 1:
	379	case 2:
	380	case 4:
	381	if (subcores_per_core == val)
	382	/* Nothing to do */
	383	goto out;
	384	break;
	385	default:
	386	return -EINVAL;
	387	}
	388
	389	rc = set_subcores_per_core(val);
	390	if (rc)
	391	return rc;
	392
	393	out:
	394	return count;
	395	}
	396
	397	static ssize_t show_subcores_per_core(struct device *dev,
	398	struct device_attribute attr, char buf)
	399	{
	400	return sprintf(buf, "%x\n", subcores_per_core);
	401	}
	402
	403	static DEVICE_ATTR(subcores_per_core, 0644,
	404	show_subcores_per_core, store_subcores_per_core);
	405
	406	static int subcore_init(void)
	407	{
0e5e7f5e ME	408	unsigned pvr_ver;
	409
	410	pvr_ver = PVR_VER(mfspr(SPRN_PVR));
	411
	412	if (pvr_ver != PVR_POWER8 &&
	413	pvr_ver != PVR_POWER8E &&
	414	pvr_ver != PVR_POWER8NVL)
e2186023 ME	415	return 0;
	416
	417	/*
	418	* We need all threads in a core to be present to split/unsplit so
	419	* continue only if max_cpus are aligned to threads_per_core.
	420	*/
	421	if (setup_max_cpus % threads_per_core)
	422	return 0;
	423
	424	BUG_ON(!alloc_cpumask_var(&cpu_offline_mask, GFP_KERNEL));
	425
	426	set_subcores_per_core(1);
	427
	428	return device_create_file(cpu_subsys.dev_root,
	429	&dev_attr_subcores_per_core);
	430	}
	431	machine_device_initcall(powernv, subcore_init);