[linux-2.6-block.git] / arch / powerpc / mm / book3s64 / mmu_context.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  MMU context allocation for 64-bit kernels.
 *
 *  Copyright (C) 2004 Anton Blanchard, IBM Corp. <anton@samba.org>
 */

#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/mm.h>
#include <linux/pkeys.h>
#include <linux/spinlock.h>
#include <linux/idr.h>
#include <linux/export.h>
#include <linux/gfp.h>
#include <linux/slab.h>
#include <linux/cpu.h>

#include <asm/mmu_context.h>
#include <asm/pgalloc.h>

#include "internal.h"

static DEFINE_IDA(mmu_context_ida);

static int alloc_context_id(int min_id, int max_id)
{
	return ida_alloc_range(&mmu_context_ida, min_id, max_id, GFP_KERNEL);
}

#ifdef CONFIG_PPC_64S_HASH_MMU
void __init hash__reserve_context_id(int id)
{
	int result = ida_alloc_range(&mmu_context_ida, id, id, GFP_KERNEL);

	WARN(result != id, "mmu: Failed to reserve context id %d (rc %d)\n", id, result);
}

int hash__alloc_context_id(void)
{
	unsigned long max;

	if (mmu_has_feature(MMU_FTR_68_BIT_VA))
		max = MAX_USER_CONTEXT;
	else
		max = MAX_USER_CONTEXT_65BIT_VA;

	return alloc_context_id(MIN_USER_CONTEXT, max);
}
EXPORT_SYMBOL_GPL(hash__alloc_context_id);
#endif

#ifdef CONFIG_PPC_64S_HASH_MMU
static int realloc_context_ids(mm_context_t *ctx)
{
	int i, id;

	/*
	 * id 0 (aka. ctx->id) is special, we always allocate a new one, even if
	 * there wasn't one allocated previously (which happens in the exec
	 * case where ctx is newly allocated).
	 *
	 * We have to be a bit careful here. We must keep the existing ids in
	 * the array, so that we can test if they're non-zero to decide if we
	 * need to allocate a new one. However in case of error we must free the
	 * ids we've allocated but *not* any of the existing ones (or risk a
	 * UAF). That's why we decrement i at the start of the error handling
	 * loop, to skip the id that we just tested but couldn't reallocate.
	 */
	for (i = 0; i < ARRAY_SIZE(ctx->extended_id); i++) {
		if (i == 0 || ctx->extended_id[i]) {
			id = hash__alloc_context_id();
			if (id < 0)
				goto error;

			ctx->extended_id[i] = id;
		}
	}

	/* The caller expects us to return id */
	return ctx->id;

error:
	for (i--; i >= 0; i--) {
		if (ctx->extended_id[i])
			ida_free(&mmu_context_ida, ctx->extended_id[i]);
	}

	return id;
}

static int hash__init_new_context(struct mm_struct *mm)
{
	int index;

	mm->context.hash_context = kmalloc(sizeof(struct hash_mm_context),
					   GFP_KERNEL);
	if (!mm->context.hash_context)
		return -ENOMEM;

	/*
	 * The old code would re-promote on fork, we don't do that when using
	 * slices as it could cause problem promoting slices that have been
	 * forced down to 4K.
	 *
	 * For book3s we have MMU_NO_CONTEXT set to be ~0. Hence check
	 * explicitly against context.id == 0. This ensures that we properly
	 * initialize context slice details for newly allocated mm's (which will
	 * have id == 0) and don't alter context slice inherited via fork (which
	 * will have id != 0).
	 *
	 * We should not be calling init_new_context() on init_mm. Hence a
	 * check against 0 is OK.
	 */
	if (mm->context.id == 0) {
		memset(mm->context.hash_context, 0, sizeof(struct hash_mm_context));
		slice_init_new_context_exec(mm);
	} else {
		/* This is fork. Copy hash_context details from current->mm */
		memcpy(mm->context.hash_context, current->mm->context.hash_context, sizeof(struct hash_mm_context));
#ifdef CONFIG_PPC_SUBPAGE_PROT
		/* inherit subpage prot details if we have one. */
		if (current->mm->context.hash_context->spt) {
			mm->context.hash_context->spt = kmalloc(sizeof(struct subpage_prot_table),
								GFP_KERNEL);
			if (!mm->context.hash_context->spt) {
				kfree(mm->context.hash_context);
				return -ENOMEM;
			}
		}
#endif
	}

	index = realloc_context_ids(&mm->context);
	if (index < 0) {
#ifdef CONFIG_PPC_SUBPAGE_PROT
		kfree(mm->context.hash_context->spt);
#endif
		kfree(mm->context.hash_context);
		return index;
	}

	pkey_mm_init(mm);
	return index;
}

void hash__setup_new_exec(void)
{
	slice_setup_new_exec();

	slb_setup_new_exec();
}
#else
static inline int hash__init_new_context(struct mm_struct *mm)
{
	BUILD_BUG();
	return 0;
}
#endif

static int radix__init_new_context(struct mm_struct *mm)
{
	unsigned long rts_field;
	int index, max_id;

	max_id = (1 << mmu_pid_bits) - 1;
	index = alloc_context_id(mmu_base_pid, max_id);
	if (index < 0)
		return index;

	/*
	 * set the process table entry,
	 */
	rts_field = radix__get_tree_size();
	process_tb[index].prtb0 = cpu_to_be64(rts_field | __pa(mm->pgd) | RADIX_PGD_INDEX_SIZE);

	/*
	 * Order the above store with subsequent update of the PID
	 * register (at which point HW can start loading/caching
	 * the entry) and the corresponding load by the MMU from
	 * the L2 cache.
	 */
	asm volatile("ptesync;isync" : : : "memory");

#ifdef CONFIG_PPC_64S_HASH_MMU
	mm->context.hash_context = NULL;
#endif

	return index;
}

int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
{
	int index;

	if (radix_enabled())
		index = radix__init_new_context(mm);
	else
		index = hash__init_new_context(mm);

	if (index < 0)
		return index;

	mm->context.id = index;

	mm->context.pte_frag = NULL;
	mm->context.pmd_frag = NULL;
#ifdef CONFIG_SPAPR_TCE_IOMMU
	mm_iommu_init(mm);
#endif
	atomic_set(&mm->context.active_cpus, 0);
	atomic_set(&mm->context.copros, 0);

	return 0;
}

void __destroy_context(int context_id)
{
	ida_free(&mmu_context_ida, context_id);
}
EXPORT_SYMBOL_GPL(__destroy_context);

static void destroy_contexts(mm_context_t *ctx)
{
	if (radix_enabled()) {
		ida_free(&mmu_context_ida, ctx->id);
	} else {
#ifdef CONFIG_PPC_64S_HASH_MMU
		int index, context_id;

		for (index = 0; index < ARRAY_SIZE(ctx->extended_id); index++) {
			context_id = ctx->extended_id[index];
			if (context_id)
				ida_free(&mmu_context_ida, context_id);
		}
		kfree(ctx->hash_context);
#else
		BUILD_BUG(); // radix_enabled() should be constant true
#endif
	}
}

static void pmd_frag_destroy(void *pmd_frag)
{
	int count;
	struct ptdesc *ptdesc;

	ptdesc = virt_to_ptdesc(pmd_frag);
	/* drop all the pending references */
	count = ((unsigned long)pmd_frag & ~PAGE_MASK) >> PMD_FRAG_SIZE_SHIFT;
	/* We allow PTE_FRAG_NR fragments from a PTE page */
	if (atomic_sub_and_test(PMD_FRAG_NR - count, &ptdesc->pt_frag_refcount)) {
		pagetable_pmd_dtor(ptdesc);
		pagetable_free(ptdesc);
	}
}

static void destroy_pagetable_cache(struct mm_struct *mm)
{
	void *frag;

	frag = mm->context.pte_frag;
	if (frag)
		pte_frag_destroy(frag);

	frag = mm->context.pmd_frag;
	if (frag)
		pmd_frag_destroy(frag);
	return;
}

void destroy_context(struct mm_struct *mm)
{
#ifdef CONFIG_SPAPR_TCE_IOMMU
	WARN_ON_ONCE(!list_empty(&mm->context.iommu_group_mem_list));
#endif
	/*
	 * For tasks which were successfully initialized we end up calling
	 * arch_exit_mmap() which clears the process table entry. And
	 * arch_exit_mmap() is called before the required fullmm TLB flush
	 * which does a RIC=2 flush. Hence for an initialized task, we do clear
	 * any cached process table entries.
	 *
	 * The condition below handles the error case during task init. We have
	 * set the process table entry early and if we fail a task
	 * initialization, we need to ensure the process table entry is zeroed.
	 * We need not worry about process table entry caches because the task
	 * never ran with the PID value.
	 */
	if (radix_enabled())
		process_tb[mm->context.id].prtb0 = 0;
	else
		subpage_prot_free(mm);
	destroy_contexts(&mm->context);
	mm->context.id = MMU_NO_CONTEXT;
}

void arch_exit_mmap(struct mm_struct *mm)
{
	destroy_pagetable_cache(mm);

	if (radix_enabled()) {
		/*
		 * Radix doesn't have a valid bit in the process table
		 * entries. However we know that at least P9 implementation
		 * will avoid caching an entry with an invalid RTS field,
		 * and 0 is invalid. So this will do.
		 *
		 * This runs before the "fullmm" tlb flush in exit_mmap,
		 * which does a RIC=2 tlbie to clear the process table
		 * entry. See the "fullmm" comments in tlb-radix.c.
		 *
		 * No barrier required here after the store because
		 * this process will do the invalidate, which starts with
		 * ptesync.
		 */
		process_tb[mm->context.id].prtb0 = 0;
	}
}

#ifdef CONFIG_PPC_RADIX_MMU
void radix__switch_mmu_context(struct mm_struct *prev, struct mm_struct *next)
{
	mtspr(SPRN_PID, next->context.id);
	isync();
}
#endif

/**
 * cleanup_cpu_mmu_context - Clean up MMU details for this CPU (newly offlined)
 *
 * This clears the CPU from mm_cpumask for all processes, and then flushes the
 * local TLB to ensure TLB coherency in case the CPU is onlined again.
 *
 * KVM guest translations are not necessarily flushed here. If KVM started
 * using mm_cpumask or the Linux APIs which do, this would have to be resolved.
 */
#ifdef CONFIG_HOTPLUG_CPU
void cleanup_cpu_mmu_context(void)
{
	int cpu = smp_processor_id();

	clear_tasks_mm_cpumask(cpu);
	tlbiel_all();
}
#endif
Commit	Line	Data
2874c5fd	1	// SPDX-License-Identifier: GPL-2.0-or-later
14cf11af PM	2	/*
	3	* MMU context allocation for 64-bit kernels.
	4	*
	5	* Copyright (C) 2004 Anton Blanchard, IBM Corp. <anton@samba.org>
14cf11af PM	6	*/
14cf11af PM	7
14cf11af PM	8	#include <linux/sched.h>
	9	#include <linux/kernel.h>
	10	#include <linux/errno.h>
	11	#include <linux/string.h>
	12	#include <linux/types.h>
	13	#include <linux/mm.h>
4fb158f6	14	#include <linux/pkeys.h>
14cf11af PM	15	#include <linux/spinlock.h>
14cf11af PM	16	#include <linux/idr.h>
4b16f8e2	17	#include <linux/export.h>
5a0e3ad6	18	#include <linux/gfp.h>
851d2e2f	19	#include <linux/slab.h>
01b0f0ea	20	#include <linux/cpu.h>
14cf11af PM	21
14cf11af PM	22	#include <asm/mmu_context.h>
5c1f6ee9	23	#include <asm/pgalloc.h>
14cf11af	24
ef1edbba ME	25	#include "internal.h"
ef1edbba ME	26
7317ac87	27	static DEFINE_IDA(mmu_context_ida);
14cf11af	28
c1ff840d	29	static int alloc_context_id(int min_id, int max_id)
14cf11af	30	{
b3fa6417	31	return ida_alloc_range(&mmu_context_ida, min_id, max_id, GFP_KERNEL);
e85a4710	32	}
a336f2f5	33
387e220a	34	#ifdef CONFIG_PPC_64S_HASH_MMU
c13f2b2b	35	void __init hash__reserve_context_id(int id)
82228e36	36	{
b3fa6417	37	int result = ida_alloc_range(&mmu_context_ida, id, id, GFP_KERNEL);
82228e36 AK	38
	39	WARN(result != id, "mmu: Failed to reserve context id %d (rc %d)\n", id, result);
	40	}
	41
a336f2f5 ME	42	int hash__alloc_context_id(void)
a336f2f5 ME	43	{
e6f81a92 AK	44	unsigned long max;
	45
	46	if (mmu_has_feature(MMU_FTR_68_BIT_VA))
	47	max = MAX_USER_CONTEXT;
	48	else
	49	max = MAX_USER_CONTEXT_65BIT_VA;
	50
	51	return alloc_context_id(MIN_USER_CONTEXT, max);
a336f2f5 ME	52	}
a336f2f5 ME	53	EXPORT_SYMBOL_GPL(hash__alloc_context_id);
387e220a	54	#endif
a336f2f5	55
387e220a	56	#ifdef CONFIG_PPC_64S_HASH_MMU
ca72d883 ME	57	static int realloc_context_ids(mm_context_t *ctx)
	58	{
	59	int i, id;
	60
	61	/*
	62	* id 0 (aka. ctx->id) is special, we always allocate a new one, even if
	63	* there wasn't one allocated previously (which happens in the exec
	64	* case where ctx is newly allocated).
	65	*
	66	* We have to be a bit careful here. We must keep the existing ids in
	67	* the array, so that we can test if they're non-zero to decide if we
	68	* need to allocate a new one. However in case of error we must free the
	69	* ids we've allocated but not any of the existing ones (or risk a
	70	* UAF). That's why we decrement i at the start of the error handling
	71	* loop, to skip the id that we just tested but couldn't reallocate.
	72	*/
	73	for (i = 0; i < ARRAY_SIZE(ctx->extended_id); i++) {
	74	if (i == 0 \|\| ctx->extended_id[i]) {
	75	id = hash__alloc_context_id();
	76	if (id < 0)
	77	goto error;
	78
	79	ctx->extended_id[i] = id;
	80	}
	81	}
	82
	83	/* The caller expects us to return id */
	84	return ctx->id;
	85
	86	error:
	87	for (i--; i >= 0; i--) {
	88	if (ctx->extended_id[i])
	89	ida_free(&mmu_context_ida, ctx->extended_id[i]);
	90	}
	91
	92	return id;
	93	}
	94
760573c1 ME	95	static int hash__init_new_context(struct mm_struct *mm)
	96	{
	97	int index;
	98
ef629cc5 AK	99	mm->context.hash_context = kmalloc(sizeof(struct hash_mm_context),
ef629cc5 AK	100	GFP_KERNEL);
65565a68	101	if (!mm->context.hash_context)
70110186	102	return -ENOMEM;
70110186	103
760573c1 ME	104	/*
	105	* The old code would re-promote on fork, we don't do that when using
	106	* slices as it could cause problem promoting slices that have been
	107	* forced down to 4K.
	108	*
	109	* For book3s we have MMU_NO_CONTEXT set to be ~0. Hence check
	110	* explicitly against context.id == 0. This ensures that we properly
	111	* initialize context slice details for newly allocated mm's (which will
	112	* have id == 0) and don't alter context slice inherited via fork (which
	113	* will have id != 0).
	114	*
	115	* We should not be calling init_new_context() on init_mm. Hence a
	116	* check against 0 is OK.
	117	*/
70110186 AK	118	if (mm->context.id == 0) {
70110186 AK	119	memset(mm->context.hash_context, 0, sizeof(struct hash_mm_context));
1753dd18	120	slice_init_new_context_exec(mm);
70110186 AK	121	} else {
	122	/* This is fork. Copy hash_context details from current->mm */
	123	memcpy(mm->context.hash_context, current->mm->context.hash_context, sizeof(struct hash_mm_context));
ef629cc5	124	#ifdef CONFIG_PPC_SUBPAGE_PROT
7a7d744f	125	/* inherit subpage prot details if we have one. */
ef629cc5 AK	126	if (current->mm->context.hash_context->spt) {
	127	mm->context.hash_context->spt = kmalloc(sizeof(struct subpage_prot_table),
	128	GFP_KERNEL);
	129	if (!mm->context.hash_context->spt) {
ef629cc5 AK	130	kfree(mm->context.hash_context);
	131	return -ENOMEM;
	132	}
	133	}
	134	#endif
65565a68	135	}
70110186	136
ca72d883	137	index = realloc_context_ids(&mm->context);
65565a68 ME	138	if (index < 0) {
	139	#ifdef CONFIG_PPC_SUBPAGE_PROT
	140	kfree(mm->context.hash_context->spt);
	141	#endif
	142	kfree(mm->context.hash_context);
ca72d883	143	return index;
70110186	144	}
760573c1	145
4fb158f6	146	pkey_mm_init(mm);
760573c1 ME	147	return index;
	148	}
	149
425d3314 NP	150	void hash__setup_new_exec(void)
	151	{
	152	slice_setup_new_exec();
5434ae74 NP	153
5434ae74 NP	154	slb_setup_new_exec();
425d3314	155	}
387e220a NP	156	#else
	157	static inline int hash__init_new_context(struct mm_struct *mm)
	158	{
	159	BUILD_BUG();
	160	return 0;
	161	}
	162	#endif
425d3314	163
760573c1	164	static int radix__init_new_context(struct mm_struct *mm)
7e381c0f AK	165	{
7e381c0f AK	166	unsigned long rts_field;
a25bd72b	167	int index, max_id;
760573c1	168
a25bd72b BH	169	max_id = (1 << mmu_pid_bits) - 1;
a25bd72b BH	170	index = alloc_context_id(mmu_base_pid, max_id);
760573c1 ME	171	if (index < 0)
760573c1 ME	172	return index;
7e381c0f AK	173
	174	/*
	175	* set the process table entry,
	176	*/
b23d9c5b	177	rts_field = radix__get_tree_size();
7e381c0f	178	process_tb[index].prtb0 = cpu_to_be64(rts_field \| __pa(mm->pgd) \| RADIX_PGD_INDEX_SIZE);
760573c1	179
3a6a0470 BH	180	/*
	181	* Order the above store with subsequent update of the PID
	182	* register (at which point HW can start loading/caching
	183	* the entry) and the corresponding load by the MMU from
	184	* the L2 cache.
	185	*/
	186	asm volatile("ptesync;isync" : : : "memory");
	187
387e220a	188	#ifdef CONFIG_PPC_64S_HASH_MMU
70110186	189	mm->context.hash_context = NULL;
387e220a	190	#endif
1ab66d1f	191
760573c1	192	return index;
7e381c0f	193	}
e85a4710 AG	194
	195	int init_new_context(struct task_struct tsk, struct mm_struct mm)
	196	{
	197	int index;
	198
760573c1 ME	199	if (radix_enabled())
	200	index = radix__init_new_context(mm);
	201	else
	202	index = hash__init_new_context(mm);
	203
e85a4710 AG	204	if (index < 0)
	205	return index;
	206
9dfe5c53	207	mm->context.id = index;
14cf11af	208
5c1f6ee9	209	mm->context.pte_frag = NULL;
8a6c697b	210	mm->context.pmd_frag = NULL;
15b244a8	211	#ifdef CONFIG_SPAPR_TCE_IOMMU
88f54a35	212	mm_iommu_init(mm);
5c1f6ee9	213	#endif
a619e59c	214	atomic_set(&mm->context.active_cpus, 0);
aff6f8cb	215	atomic_set(&mm->context.copros, 0);
a619e59c	216
14cf11af PM	217	return 0;
	218	}
	219
e85a4710	220	void __destroy_context(int context_id)
14cf11af	221	{
b3fa6417	222	ida_free(&mmu_context_ida, context_id);
e85a4710 AG	223	}
e85a4710 AG	224	EXPORT_SYMBOL_GPL(__destroy_context);
14cf11af	225
f384796c AK	226	static void destroy_contexts(mm_context_t *ctx)
f384796c AK	227	{
387e220a NP	228	if (radix_enabled()) {
	229	ida_free(&mmu_context_ida, ctx->id);
	230	} else {
	231	#ifdef CONFIG_PPC_64S_HASH_MMU
	232	int index, context_id;
f384796c	233
387e220a NP	234	for (index = 0; index < ARRAY_SIZE(ctx->extended_id); index++) {
	235	context_id = ctx->extended_id[index];
	236	if (context_id)
	237	ida_free(&mmu_context_ida, context_id);
	238	}
	239	kfree(ctx->hash_context);
	240	#else
	241	BUILD_BUG(); // radix_enabled() should be constant true
	242	#endif
f384796c	243	}
f384796c AK	244	}
f384796c AK	245
8a6c697b AK	246	static void pmd_frag_destroy(void *pmd_frag)
	247	{
	248	int count;
4eaca961	249	struct ptdesc *ptdesc;
8a6c697b	250
4eaca961	251	ptdesc = virt_to_ptdesc(pmd_frag);
8a6c697b AK	252	/* drop all the pending references */
	253	count = ((unsigned long)pmd_frag & ~PAGE_MASK) >> PMD_FRAG_SIZE_SHIFT;
	254	/* We allow PTE_FRAG_NR fragments from a PTE page */
4eaca961 VMO	255	if (atomic_sub_and_test(PMD_FRAG_NR - count, &ptdesc->pt_frag_refcount)) {
	256	pagetable_pmd_dtor(ptdesc);
	257	pagetable_free(ptdesc);
8a6c697b AK	258	}
	259	}
	260
34c604d2	261	static void destroy_pagetable_cache(struct mm_struct *mm)
8a6c697b AK	262	{
	263	void *frag;
	264
	265	frag = mm->context.pte_frag;
	266	if (frag)
	267	pte_frag_destroy(frag);
	268
	269	frag = mm->context.pmd_frag;
	270	if (frag)
	271	pmd_frag_destroy(frag);
	272	return;
	273	}
	274
e85a4710 AG	275	void destroy_context(struct mm_struct *mm)
e85a4710 AG	276	{
15b244a8	277	#ifdef CONFIG_SPAPR_TCE_IOMMU
4b6fad70	278	WARN_ON_ONCE(!list_empty(&mm->context.iommu_group_mem_list));
15b244a8	279	#endif
7aec584e AK	280	/*
	281	* For tasks which were successfully initialized we end up calling
	282	* arch_exit_mmap() which clears the process table entry. And
	283	* arch_exit_mmap() is called before the required fullmm TLB flush
	284	* which does a RIC=2 flush. Hence for an initialized task, we do clear
	285	* any cached process table entries.
	286	*
	287	* The condition below handles the error case during task init. We have
	288	* set the process table entry early and if we fail a task
	289	* initialization, we need to ensure the process table entry is zeroed.
	290	* We need not worry about process table entry caches because the task
	291	* never ran with the PID value.
	292	*/
30b49ec7	293	if (radix_enabled())
7aec584e	294	process_tb[mm->context.id].prtb0 = 0;
30b49ec7 NP	295	else
30b49ec7 NP	296	subpage_prot_free(mm);
f384796c	297	destroy_contexts(&mm->context);
30b49ec7 NP	298	mm->context.id = MMU_NO_CONTEXT;
	299	}
	300
	301	void arch_exit_mmap(struct mm_struct *mm)
	302	{
34c604d2 NP	303	destroy_pagetable_cache(mm);
34c604d2 NP	304
c6bb0b8d BH	305	if (radix_enabled()) {
	306	/*
	307	* Radix doesn't have a valid bit in the process table
	308	* entries. However we know that at least P9 implementation
	309	* will avoid caching an entry with an invalid RTS field,
	310	* and 0 is invalid. So this will do.
30b49ec7 NP	311	*
	312	* This runs before the "fullmm" tlb flush in exit_mmap,
	313	* which does a RIC=2 tlbie to clear the process table
	314	* entry. See the "fullmm" comments in tlb-radix.c.
	315	*
	316	* No barrier required here after the store because
	317	* this process will do the invalidate, which starts with
	318	* ptesync.
c6bb0b8d BH	319	*/
c6bb0b8d BH	320	process_tb[mm->context.id].prtb0 = 0;
30b49ec7	321	}
14cf11af	322	}
7e381c0f AK	323
	324	#ifdef CONFIG_PPC_RADIX_MMU
	325	void radix__switch_mmu_context(struct mm_struct prev, struct mm_struct next)
	326	{
2bf1071a NP	327	mtspr(SPRN_PID, next->context.id);
2bf1071a NP	328	isync();
7e381c0f AK	329	}
7e381c0f AK	330	#endif
01b0f0ea NP	331
	332	/**
	333	* cleanup_cpu_mmu_context - Clean up MMU details for this CPU (newly offlined)
	334	*
	335	* This clears the CPU from mm_cpumask for all processes, and then flushes the
	336	* local TLB to ensure TLB coherency in case the CPU is onlined again.
	337	*
	338	* KVM guest translations are not necessarily flushed here. If KVM started
	339	* using mm_cpumask or the Linux APIs which do, this would have to be resolved.
	340	*/
	341	#ifdef CONFIG_HOTPLUG_CPU
	342	void cleanup_cpu_mmu_context(void)
	343	{
	344	int cpu = smp_processor_id();
	345
	346	clear_tasks_mm_cpumask(cpu);
	347	tlbiel_all();
	348	}
	349	#endif