linux/arch/powerpc/mm/tlb-radix.c

/*
 * TLB flush routines for radix kernels.
 *
 * Copyright 2015-2016, Aneesh Kumar K.V, IBM Corporation.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/mm.h>
#include <linux/hugetlb.h>
#include <linux/memblock.h>

#include <asm/ppc-opcode.h>
#include <asm/tlb.h>
#include <asm/tlbflush.h>
#include <asm/trace.h>
#include <asm/cputhreads.h>

#define RIC_FLUSH_TLB 0
#define RIC_FLUSH_PWC 1
#define RIC_FLUSH_ALL 2

/*
 * tlbiel instruction for radix, set invalidation
 * i.e., r=1 and is=01 or is=10 or is=11
 */
static inline void tlbiel_radix_set_isa300(unsigned int set, unsigned int is,
					unsigned int pid,
					unsigned int ric, unsigned int prs)
{
	unsigned long rb;
	unsigned long rs;

	rb = (set << PPC_BITLSHIFT(51)) | (is << PPC_BITLSHIFT(53));
	rs = ((unsigned long)pid << PPC_BITLSHIFT(31));

	asm volatile(PPC_TLBIEL(%0, %1, %2, %3, 1)
		     : : "r"(rb), "r"(rs), "i"(ric), "i"(prs)
		     : "memory");
}

static void tlbiel_all_isa300(unsigned int num_sets, unsigned int is)
{
	unsigned int set;

	asm volatile("ptesync": : :"memory");

	/*
	 * Flush the first set of the TLB, and the entire Page Walk Cache
	 * and partition table entries. Then flush the remaining sets of the
	 * TLB.
	 */
	tlbiel_radix_set_isa300(0, is, 0, RIC_FLUSH_ALL, 0);
	for (set = 1; set < num_sets; set++)
		tlbiel_radix_set_isa300(set, is, 0, RIC_FLUSH_TLB, 0);

	/* Do the same for process scoped entries. */
	tlbiel_radix_set_isa300(0, is, 0, RIC_FLUSH_ALL, 1);
	for (set = 1; set < num_sets; set++)
		tlbiel_radix_set_isa300(set, is, 0, RIC_FLUSH_TLB, 1);

	asm volatile("ptesync": : :"memory");
}

void radix__tlbiel_all(unsigned int action)
{
	unsigned int is;

	switch (action) {
	case TLB_INVAL_SCOPE_GLOBAL:
		is = 3;
		break;
	case TLB_INVAL_SCOPE_LPID:
		is = 2;
		break;
	default:
		BUG();
	}

	if (early_cpu_has_feature(CPU_FTR_ARCH_300))
		tlbiel_all_isa300(POWER9_TLB_SETS_RADIX, is);
	else
		WARN(1, "%s called on pre-POWER9 CPU\n", __func__);

	asm volatile(PPC_INVALIDATE_ERAT "; isync" : : :"memory");
}

static inline void __tlbiel_pid(unsigned long pid, int set,
				unsigned long ric)
{
	unsigned long rb,rs,prs,r;

	rb = PPC_BIT(53); /* IS = 1 */
	rb |= set << PPC_BITLSHIFT(51);
	rs = ((unsigned long)pid) << PPC_BITLSHIFT(31);
	prs = 1; /* process scoped */
	r = 1;   /* radix format */

	asm volatile(PPC_TLBIEL(%0, %4, %3, %2, %1)
		     : : "r"(rb), "i"(r), "i"(prs), "i"(ric), "r"(rs) : "memory");
	trace_tlbie(0, 1, rb, rs, ric, prs, r);
}

static inline void __tlbie_pid(unsigned long pid, unsigned long ric)
{
	unsigned long rb,rs,prs,r;

	rb = PPC_BIT(53); /* IS = 1 */
	rs = pid << PPC_BITLSHIFT(31);
	prs = 1; /* process scoped */
	r = 1;   /* radix format */

	asm volatile(PPC_TLBIE_5(%0, %4, %3, %2, %1)
		     : : "r"(rb), "i"(r), "i"(prs), "i"(ric), "r"(rs) : "memory");
	trace_tlbie(0, 0, rb, rs, ric, prs, r);
}

static inline void __tlbiel_va(unsigned long va, unsigned long pid,
			       unsigned long ap, unsigned long ric)
{
	unsigned long rb,rs,prs,r;

	rb = va & ~(PPC_BITMASK(52, 63));
	rb |= ap << PPC_BITLSHIFT(58);
	rs = pid << PPC_BITLSHIFT(31);
	prs = 1; /* process scoped */
	r = 1;   /* radix format */

	asm volatile(PPC_TLBIEL(%0, %4, %3, %2, %1)
		     : : "r"(rb), "i"(r), "i"(prs), "i"(ric), "r"(rs) : "memory");
	trace_tlbie(0, 1, rb, rs, ric, prs, r);
}

static inline void __tlbie_va(unsigned long va, unsigned long pid,
			      unsigned long ap, unsigned long ric)
{
	unsigned long rb,rs,prs,r;

	rb = va & ~(PPC_BITMASK(52, 63));
	rb |= ap << PPC_BITLSHIFT(58);
	rs = pid << PPC_BITLSHIFT(31);
	prs = 1; /* process scoped */
	r = 1;   /* radix format */

	asm volatile(PPC_TLBIE_5(%0, %4, %3, %2, %1)
		     : : "r"(rb), "i"(r), "i"(prs), "i"(ric), "r"(rs) : "memory");
	trace_tlbie(0, 0, rb, rs, ric, prs, r);
}

static inline void fixup_tlbie(void)
{
	unsigned long pid = 0;
	unsigned long va = ((1UL << 52) - 1);

	if (cpu_has_feature(CPU_FTR_P9_TLBIE_BUG)) {
		asm volatile("ptesync": : :"memory");
		__tlbie_va(va, pid, mmu_get_ap(MMU_PAGE_64K), RIC_FLUSH_TLB);
	}
}

/*
 * We use 128 set in radix mode and 256 set in hpt mode.
 */
static inline void _tlbiel_pid(unsigned long pid, unsigned long ric)
{
	int set;

	asm volatile("ptesync": : :"memory");

	/*
	 * Flush the first set of the TLB, and if we're doing a RIC_FLUSH_ALL,
	 * also flush the entire Page Walk Cache.
	 */
	__tlbiel_pid(pid, 0, ric);

	/* For PWC, only one flush is needed */
	if (ric == RIC_FLUSH_PWC) {
		asm volatile("ptesync": : :"memory");
		return;
	}

	/* For the remaining sets, just flush the TLB */
	for (set = 1; set < POWER9_TLB_SETS_RADIX ; set++)
		__tlbiel_pid(pid, set, RIC_FLUSH_TLB);

	asm volatile("ptesync": : :"memory");
	asm volatile(PPC_INVALIDATE_ERAT "; isync" : : :"memory");
}

static inline void _tlbie_pid(unsigned long pid, unsigned long ric)
{
	asm volatile("ptesync": : :"memory");

	/*
	 * Workaround the fact that the "ric" argument to __tlbie_pid
	 * must be a compile-time contraint to match the "i" constraint
	 * in the asm statement.
	 */
	switch (ric) {
	case RIC_FLUSH_TLB:
		__tlbie_pid(pid, RIC_FLUSH_TLB);
		break;
	case RIC_FLUSH_PWC:
		__tlbie_pid(pid, RIC_FLUSH_PWC);
		break;
	case RIC_FLUSH_ALL:
	default:
		__tlbie_pid(pid, RIC_FLUSH_ALL);
	}
	fixup_tlbie();
	asm volatile("eieio; tlbsync; ptesync": : :"memory");
}

static inline void __tlbiel_va_range(unsigned long start, unsigned long end,
				    unsigned long pid, unsigned long page_size,
				    unsigned long psize)
{
	unsigned long addr;
	unsigned long ap = mmu_get_ap(psize);

	for (addr = start; addr < end; addr += page_size)
		__tlbiel_va(addr, pid, ap, RIC_FLUSH_TLB);
}

static inline void _tlbiel_va(unsigned long va, unsigned long pid,
			      unsigned long psize, unsigned long ric)
{
	unsigned long ap = mmu_get_ap(psize);

	asm volatile("ptesync": : :"memory");
	__tlbiel_va(va, pid, ap, ric);
	asm volatile("ptesync": : :"memory");
}

static inline void _tlbiel_va_range(unsigned long start, unsigned long end,
				    unsigned long pid, unsigned long page_size,
				    unsigned long psize, bool also_pwc)
{
	asm volatile("ptesync": : :"memory");
	if (also_pwc)
		__tlbiel_pid(pid, 0, RIC_FLUSH_PWC);
	__tlbiel_va_range(start, end, pid, page_size, psize);
	asm volatile("ptesync": : :"memory");
}

static inline void __tlbie_va_range(unsigned long start, unsigned long end,
				    unsigned long pid, unsigned long page_size,
				    unsigned long psize)
{
	unsigned long addr;
	unsigned long ap = mmu_get_ap(psize);

	for (addr = start; addr < end; addr += page_size)
		__tlbie_va(addr, pid, ap, RIC_FLUSH_TLB);
}

static inline void _tlbie_va(unsigned long va, unsigned long pid,
			      unsigned long psize, unsigned long ric)
{
	unsigned long ap = mmu_get_ap(psize);

	asm volatile("ptesync": : :"memory");
	__tlbie_va(va, pid, ap, ric);
	fixup_tlbie();
	asm volatile("eieio; tlbsync; ptesync": : :"memory");
}

static inline void _tlbie_va_range(unsigned long start, unsigned long end,
				    unsigned long pid, unsigned long page_size,
				    unsigned long psize, bool also_pwc)
{
	asm volatile("ptesync": : :"memory");
	if (also_pwc)
		__tlbie_pid(pid, RIC_FLUSH_PWC);
	__tlbie_va_range(start, end, pid, page_size, psize);
	fixup_tlbie();
	asm volatile("eieio; tlbsync; ptesync": : :"memory");
}

/*
 * Base TLB flushing operations:
 *
 *  - flush_tlb_mm(mm) flushes the specified mm context TLB's
 *  - flush_tlb_page(vma, vmaddr) flushes one page
 *  - flush_tlb_range(vma, start, end) flushes a range of pages
 *  - flush_tlb_kernel_range(start, end) flushes kernel pages
 *
 *  - local_* variants of page and mm only apply to the current
 *    processor
 */
void radix__local_flush_tlb_mm(struct mm_struct *mm)
{
	unsigned long pid;

	preempt_disable();
	pid = mm->context.id;
	if (pid != MMU_NO_CONTEXT)
		_tlbiel_pid(pid, RIC_FLUSH_TLB);
	preempt_enable();
}
EXPORT_SYMBOL(radix__local_flush_tlb_mm);

#ifndef CONFIG_SMP
void radix__local_flush_all_mm(struct mm_struct *mm)
{
	unsigned long pid;

	preempt_disable();
	pid = mm->context.id;
	if (pid != MMU_NO_CONTEXT)
		_tlbiel_pid(pid, RIC_FLUSH_ALL);
	preempt_enable();
}
EXPORT_SYMBOL(radix__local_flush_all_mm);
#endif /* CONFIG_SMP */

void radix__local_flush_tlb_page_psize(struct mm_struct *mm, unsigned long vmaddr,
				       int psize)
{
	unsigned long pid;

	preempt_disable();
	pid = mm->context.id;
	if (pid != MMU_NO_CONTEXT)
		_tlbiel_va(vmaddr, pid, psize, RIC_FLUSH_TLB);
	preempt_enable();
}

void radix__local_flush_tlb_page(struct vm_area_struct *vma, unsigned long vmaddr)
{
#ifdef CONFIG_HUGETLB_PAGE
	/* need the return fix for nohash.c */
	if (is_vm_hugetlb_page(vma))
		return radix__local_flush_hugetlb_page(vma, vmaddr);
#endif
	radix__local_flush_tlb_page_psize(vma->vm_mm, vmaddr, mmu_virtual_psize);
}
EXPORT_SYMBOL(radix__local_flush_tlb_page);

static bool mm_needs_flush_escalation(struct mm_struct *mm)
{
	/*
	 * P9 nest MMU has issues with the page walk cache
	 * caching PTEs and not flushing them properly when
	 * RIC = 0 for a PID/LPID invalidate
	 */
	return atomic_read(&mm->context.copros) != 0;
}

#ifdef CONFIG_SMP
void radix__flush_tlb_mm(struct mm_struct *mm)
{
	unsigned long pid;

	pid = mm->context.id;
	if (unlikely(pid == MMU_NO_CONTEXT))
		return;

	preempt_disable();
	if (!mm_is_thread_local(mm)) {
		if (mm_needs_flush_escalation(mm))
			_tlbie_pid(pid, RIC_FLUSH_ALL);
		else
			_tlbie_pid(pid, RIC_FLUSH_TLB);
	} else
		_tlbiel_pid(pid, RIC_FLUSH_TLB);
	preempt_enable();
}
EXPORT_SYMBOL(radix__flush_tlb_mm);

void radix__flush_all_mm(struct mm_struct *mm)
{
	unsigned long pid;

	pid = mm->context.id;
	if (unlikely(pid == MMU_NO_CONTEXT))
		return;

	preempt_disable();
	if (!mm_is_thread_local(mm))
		_tlbie_pid(pid, RIC_FLUSH_ALL);
	else
		_tlbiel_pid(pid, RIC_FLUSH_ALL);
	preempt_enable();
}
EXPORT_SYMBOL(radix__flush_all_mm);

void radix__flush_tlb_pwc(struct mmu_gather *tlb, unsigned long addr)
{
	tlb->need_flush_all = 1;
}
EXPORT_SYMBOL(radix__flush_tlb_pwc);

void radix__flush_tlb_page_psize(struct mm_struct *mm, unsigned long vmaddr,
				 int psize)
{
	unsigned long pid;

	pid = mm->context.id;
	if (unlikely(pid == MMU_NO_CONTEXT))
		return;

	preempt_disable();
	if (!mm_is_thread_local(mm))
		_tlbie_va(vmaddr, pid, psize, RIC_FLUSH_TLB);
	else
		_tlbiel_va(vmaddr, pid, psize, RIC_FLUSH_TLB);
	preempt_enable();
}

void radix__flush_tlb_page(struct vm_area_struct *vma, unsigned long vmaddr)
{
#ifdef CONFIG_HUGETLB_PAGE
	if (is_vm_hugetlb_page(vma))
		return radix__flush_hugetlb_page(vma, vmaddr);
#endif
	radix__flush_tlb_page_psize(vma->vm_mm, vmaddr, mmu_virtual_psize);
}
EXPORT_SYMBOL(radix__flush_tlb_page);

#else /* CONFIG_SMP */
#define radix__flush_all_mm radix__local_flush_all_mm
#endif /* CONFIG_SMP */

void radix__flush_tlb_kernel_range(unsigned long start, unsigned long end)
{
	_tlbie_pid(0, RIC_FLUSH_ALL);
}
EXPORT_SYMBOL(radix__flush_tlb_kernel_range);

#define TLB_FLUSH_ALL -1UL

/*
 * Number of pages above which we invalidate the entire PID rather than
 * flush individual pages, for local and global flushes respectively.
 *
 * tlbie goes out to the interconnect and individual ops are more costly.
 * It also does not iterate over sets like the local tlbiel variant when
 * invalidating a full PID, so it has a far lower threshold to change from
 * individual page flushes to full-pid flushes.
 */
static unsigned long tlb_single_page_flush_ceiling __read_mostly = 33;
static unsigned long tlb_local_single_page_flush_ceiling __read_mostly = POWER9_TLB_SETS_RADIX * 2;

void radix__flush_tlb_range(struct vm_area_struct *vma, unsigned long start,
		     unsigned long end)

{
	struct mm_struct *mm = vma->vm_mm;
	unsigned long pid;
	unsigned int page_shift = mmu_psize_defs[mmu_virtual_psize].shift;
	unsigned long page_size = 1UL << page_shift;
	unsigned long nr_pages = (end - start) >> page_shift;
	bool local, full;

#ifdef CONFIG_HUGETLB_PAGE
	if (is_vm_hugetlb_page(vma))
		return radix__flush_hugetlb_tlb_range(vma, start, end);
#endif

	pid = mm->context.id;
	if (unlikely(pid == MMU_NO_CONTEXT))
		return;

	preempt_disable();
	if (mm_is_thread_local(mm)) {
		local = true;
		full = (end == TLB_FLUSH_ALL ||
				nr_pages > tlb_local_single_page_flush_ceiling);
	} else {
		local = false;
		full = (end == TLB_FLUSH_ALL ||
				nr_pages > tlb_single_page_flush_ceiling);
	}

	if (full) {
		if (local) {
			_tlbiel_pid(pid, RIC_FLUSH_TLB);
		} else {
			if (mm_needs_flush_escalation(mm))
				_tlbie_pid(pid, RIC_FLUSH_ALL);
			else
				_tlbie_pid(pid, RIC_FLUSH_TLB);
		}
	} else {
		bool hflush = false;
		unsigned long hstart, hend;

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
		hstart = (start + HPAGE_PMD_SIZE - 1) >> HPAGE_PMD_SHIFT;
		hend = end >> HPAGE_PMD_SHIFT;
		if (hstart < hend) {
			hstart <<= HPAGE_PMD_SHIFT;
			hend <<= HPAGE_PMD_SHIFT;
			hflush = true;
		}
#endif

		asm volatile("ptesync": : :"memory");
		if (local) {
			__tlbiel_va_range(start, end, pid, page_size, mmu_virtual_psize);
			if (hflush)
				__tlbiel_va_range(hstart, hend, pid,
						HPAGE_PMD_SIZE, MMU_PAGE_2M);
			asm volatile("ptesync": : :"memory");
		} else {
			__tlbie_va_range(start, end, pid, page_size, mmu_virtual_psize);
			if (hflush)
				__tlbie_va_range(hstart, hend, pid,
						HPAGE_PMD_SIZE, MMU_PAGE_2M);
			fixup_tlbie();
			asm volatile("eieio; tlbsync; ptesync": : :"memory");
		}
	}
	preempt_enable();
}
EXPORT_SYMBOL(radix__flush_tlb_range);

static int radix_get_mmu_psize(int page_size)
{
	int psize;

	if (page_size == (1UL << mmu_psize_defs[mmu_virtual_psize].shift))
		psize = mmu_virtual_psize;
	else if (page_size == (1UL << mmu_psize_defs[MMU_PAGE_2M].shift))
		psize = MMU_PAGE_2M;
	else if (page_size == (1UL << mmu_psize_defs[MMU_PAGE_1G].shift))
		psize = MMU_PAGE_1G;
	else
		return -1;
	return psize;
}

static void radix__flush_tlb_pwc_range_psize(struct mm_struct *mm, unsigned long start,
				  unsigned long end, int psize);

void radix__tlb_flush(struct mmu_gather *tlb)
{
	int psize = 0;
	struct mm_struct *mm = tlb->mm;
	int page_size = tlb->page_size;

	/*
	 * if page size is not something we understand, do a full mm flush
	 *
	 * A "fullmm" flush must always do a flush_all_mm (RIC=2) flush
	 * that flushes the process table entry cache upon process teardown.
	 * See the comment for radix in arch_exit_mmap().
	 */
	if (tlb->fullmm) {
		radix__flush_all_mm(mm);
	} else if ( (psize = radix_get_mmu_psize(page_size)) == -1) {
		if (!tlb->need_flush_all)
			radix__flush_tlb_mm(mm);
		else
			radix__flush_all_mm(mm);
	} else {
		unsigned long start = tlb->start;
		unsigned long end = tlb->end;

		if (!tlb->need_flush_all)
			radix__flush_tlb_range_psize(mm, start, end, psize);
		else
			radix__flush_tlb_pwc_range_psize(mm, start, end, psize);
	}
	tlb->need_flush_all = 0;
}

static inline void __radix__flush_tlb_range_psize(struct mm_struct *mm,
				unsigned long start, unsigned long end,
				int psize, bool also_pwc)
{
	unsigned long pid;
	unsigned int page_shift = mmu_psize_defs[psize].shift;
	unsigned long page_size = 1UL << page_shift;
	unsigned long nr_pages = (end - start) >> page_shift;
	bool local, full;

	pid = mm->context.id;
	if (unlikely(pid == MMU_NO_CONTEXT))
		return;

	preempt_disable();
	if (mm_is_thread_local(mm)) {
		local = true;
		full = (end == TLB_FLUSH_ALL ||
				nr_pages > tlb_local_single_page_flush_ceiling);
	} else {
		local = false;
		full = (end == TLB_FLUSH_ALL ||
				nr_pages > tlb_single_page_flush_ceiling);
	}

	if (full) {
		if (!local && mm_needs_flush_escalation(mm))
			also_pwc = true;

		if (local)
			_tlbiel_pid(pid, also_pwc ? RIC_FLUSH_ALL : RIC_FLUSH_TLB);
		else
			_tlbie_pid(pid, also_pwc ? RIC_FLUSH_ALL: RIC_FLUSH_TLB);
	} else {
		if (local)
			_tlbiel_va_range(start, end, pid, page_size, psize, also_pwc);
		else
			_tlbie_va_range(start, end, pid, page_size, psize, also_pwc);
	}
	preempt_enable();
}

void radix__flush_tlb_range_psize(struct mm_struct *mm, unsigned long start,
				  unsigned long end, int psize)
{
	return __radix__flush_tlb_range_psize(mm, start, end, psize, false);
}

static void radix__flush_tlb_pwc_range_psize(struct mm_struct *mm, unsigned long start,
				  unsigned long end, int psize)
{
	__radix__flush_tlb_range_psize(mm, start, end, psize, true);
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
void radix__flush_tlb_collapsed_pmd(struct mm_struct *mm, unsigned long addr)
{
	unsigned long pid, end;

	pid = mm->context.id;
	if (unlikely(pid == MMU_NO_CONTEXT))
		return;

	/* 4k page size, just blow the world */
	if (PAGE_SIZE == 0x1000) {
		radix__flush_all_mm(mm);
		return;
	}

	end = addr + HPAGE_PMD_SIZE;

	/* Otherwise first do the PWC, then iterate the pages. */
	preempt_disable();

	if (mm_is_thread_local(mm)) {
		_tlbiel_va_range(addr, end, pid, PAGE_SIZE, mmu_virtual_psize, true);
	} else {
		_tlbie_va_range(addr, end, pid, PAGE_SIZE, mmu_virtual_psize, true);
	}

	preempt_enable();
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

void radix__flush_pmd_tlb_range(struct vm_area_struct *vma,
				unsigned long start, unsigned long end)
{
	radix__flush_tlb_range_psize(vma->vm_mm, start, end, MMU_PAGE_2M);
}
EXPORT_SYMBOL(radix__flush_pmd_tlb_range);

void radix__flush_tlb_all(void)
{
	unsigned long rb,prs,r,rs;
	unsigned long ric = RIC_FLUSH_ALL;

	rb = 0x3 << PPC_BITLSHIFT(53); /* IS = 3 */
	prs = 0; /* partition scoped */
	r = 1;   /* radix format */
	rs = 1 & ((1UL << 32) - 1); /* any LPID value to flush guest mappings */

	asm volatile("ptesync": : :"memory");
	/*
	 * now flush guest entries by passing PRS = 1 and LPID != 0
	 */
	asm volatile(PPC_TLBIE_5(%0, %4, %3, %2, %1)
		     : : "r"(rb), "i"(r), "i"(1), "i"(ric), "r"(rs) : "memory");
	/*
	 * now flush host entires by passing PRS = 0 and LPID == 0
	 */
	asm volatile(PPC_TLBIE_5(%0, %4, %3, %2, %1)
		     : : "r"(rb), "i"(r), "i"(prs), "i"(ric), "r"(0) : "memory");
	asm volatile("eieio; tlbsync; ptesync": : :"memory");
}

void radix__flush_tlb_pte_p9_dd1(unsigned long old_pte, struct mm_struct *mm,
				 unsigned long address)
{
	/*
	 * We track page size in pte only for DD1, So we can
	 * call this only on DD1.
	 */
	if (!cpu_has_feature(CPU_FTR_POWER9_DD1)) {
		VM_WARN_ON(1);
		return;
	}

	if (old_pte & R_PAGE_LARGE)
		radix__flush_tlb_page_psize(mm, address, MMU_PAGE_2M);
	else
		radix__flush_tlb_page_psize(mm, address, mmu_virtual_psize);
}

#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
extern void radix_kvm_prefetch_workaround(struct mm_struct *mm)
{
	unsigned long pid = mm->context.id;

	if (unlikely(pid == MMU_NO_CONTEXT))
		return;

	/*
	 * If this context hasn't run on that CPU before and KVM is
	 * around, there's a slim chance that the guest on another
	 * CPU just brought in obsolete translation into the TLB of
	 * this CPU due to a bad prefetch using the guest PID on
	 * the way into the hypervisor.
	 *
	 * We work around this here. If KVM is possible, we check if
	 * any sibling thread is in KVM. If it is, the window may exist
	 * and thus we flush that PID from the core.
	 *
	 * A potential future improvement would be to mark which PIDs
	 * have never been used on the system and avoid it if the PID
	 * is new and the process has no other cpumask bit set.
	 */
	if (cpu_has_feature(CPU_FTR_HVMODE) && radix_enabled()) {
		int cpu = smp_processor_id();
		int sib = cpu_first_thread_sibling(cpu);
		bool flush = false;

		for (; sib <= cpu_last_thread_sibling(cpu) && !flush; sib++) {
			if (sib == cpu)
				continue;
			if (paca_ptrs[sib]->kvm_hstate.kvm_vcpu)
				flush = true;
		}
		if (flush)
			_tlbiel_pid(pid, RIC_FLUSH_ALL);
	}
}
EXPORT_SYMBOL_GPL(radix_kvm_prefetch_workaround);
#endif /* CONFIG_KVM_BOOK3S_HV_POSSIBLE */