hugetlbpage.c

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/*
 * PPC64 (POWER4) Huge TLB Page Support for Kernel.
 *
 * Copyright (C) 2003 David Gibson, IBM Corporation.
 *
 * Based on the IA-32 version:
 * Copyright (C) 2002, Rohit Seth <[e-mail]>
 */

#include <linux/init.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/hugetlb.h>
#include <linux/pagemap.h>
#include <linux/smp_lock.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/sysctl.h>
#include <asm/mman.h>
#include <asm/pgalloc.h>
#include <asm/tlb.h>
#include <asm/tlbflush.h>
#include <asm/mmu_context.h>
#include <asm/machdep.h>
#include <asm/cputable.h>
#include <asm/tlb.h>

#include <linux/sysctl.h>

#define NUM_LOW_AREAS	(0x100000000UL >> SID_SHIFT)
#define NUM_HIGH_AREAS	(PGTABLE_RANGE >> HTLB_AREA_SHIFT)

/* Modelled after find_linux_pte() */
pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
{
	pgd_t *pg;
	pud_t *pu;
	pmd_t *pm;
	pte_t *pt;

	BUG_ON(! in_hugepage_area(mm->context, addr));

	addr &= HPAGE_MASK;

	pg = pgd_offset(mm, addr);
	if (!pgd_none(*pg)) {
		pu = pud_offset(pg, addr);
		if (!pud_none(*pu)) {
			pm = pmd_offset(pu, addr);
			pt = (pte_t *)pm;
			BUG_ON(!pmd_none(*pm)
			       && !(pte_present(*pt) && pte_huge(*pt)));
			return pt;
		}
	}

	return NULL;
}

pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr)
{
	pgd_t *pg;
	pud_t *pu;
	pmd_t *pm;
	pte_t *pt;

	BUG_ON(! in_hugepage_area(mm->context, addr));

	addr &= HPAGE_MASK;

	pg = pgd_offset(mm, addr);
	pu = pud_alloc(mm, pg, addr);

	if (pu) {
		pm = pmd_alloc(mm, pu, addr);
		if (pm) {
			pt = (pte_t *)pm;
			BUG_ON(!pmd_none(*pm)
			       && !(pte_present(*pt) && pte_huge(*pt)));
			return pt;
		}
	}

	return NULL;
}

#define HUGEPTE_BATCH_SIZE	(HPAGE_SIZE / PMD_SIZE)

void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
		     pte_t *ptep, pte_t pte)
{
	int i;

	if (pte_present(*ptep)) {
		pte_clear(mm, addr, ptep);
		flush_tlb_pending();
	}

	for (i = 0; i < HUGEPTE_BATCH_SIZE; i++) {
		*ptep = __pte(pte_val(pte) & ~_PAGE_HPTEFLAGS);
		ptep++;
	}
}

pte_t huge_ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
			      pte_t *ptep)
{
	unsigned long old = pte_update(ptep, ~0UL);
	int i;

	if (old & _PAGE_HASHPTE)
		hpte_update(mm, addr, old, 0);

	for (i = 1; i < HUGEPTE_BATCH_SIZE; i++)
		ptep[i] = __pte(0);

	return __pte(old);
}

/*
 * This function checks for proper alignment of input addr and len parameters.
 */
int is_aligned_hugepage_range(unsigned long addr, unsigned long len)
{
	if (len & ~HPAGE_MASK)
		return -EINVAL;
	if (addr & ~HPAGE_MASK)
		return -EINVAL;
	if (! (within_hugepage_low_range(addr, len)
	       || within_hugepage_high_range(addr, len)) )
		return -EINVAL;
	return 0;
}

static void flush_low_segments(void *parm)
{
	u16 areas = (unsigned long) parm;
	unsigned long i;

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

	BUILD_BUG_ON((sizeof(areas)*8) != NUM_LOW_AREAS);

	for (i = 0; i < NUM_LOW_AREAS; i++) {
		if (! (areas & (1U << i)))
			continue;
		asm volatile("slbie %0"
			     : : "r" ((i << SID_SHIFT) | SLBIE_C));
	}

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

static void flush_high_segments(void *parm)
{
	u16 areas = (unsigned long) parm;
	unsigned long i, j;

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

	BUILD_BUG_ON((sizeof(areas)*8) != NUM_HIGH_AREAS);

	for (i = 0; i < NUM_HIGH_AREAS; i++) {
		if (! (areas & (1U << i)))
			continue;
		for (j = 0; j < (1UL << (HTLB_AREA_SHIFT-SID_SHIFT)); j++)
			asm volatile("slbie %0"
				     :: "r" (((i << HTLB_AREA_SHIFT)
					     + (j << SID_SHIFT)) | SLBIE_C));
	}

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

static int prepare_low_area_for_htlb(struct mm_struct *mm, unsigned long area)
{
	unsigned long start = area << SID_SHIFT;
	unsigned long end = (area+1) << SID_SHIFT;
	struct vm_area_struct *vma;

	BUG_ON(area >= NUM_LOW_AREAS);

	/* Check no VMAs are in the region */
	vma = find_vma(mm, start);
	if (vma && (vma->vm_start < end))
		return -EBUSY;

	return 0;
}

static int prepare_high_area_for_htlb(struct mm_struct *mm, unsigned long area)
{
	unsigned long start = area << HTLB_AREA_SHIFT;
	unsigned long end = (area+1) << HTLB_AREA_SHIFT;
	struct vm_area_struct *vma;

	BUG_ON(area >= NUM_HIGH_AREAS);

	/* Check no VMAs are in the region */
	vma = find_vma(mm, start);
	if (vma && (vma->vm_start < end))
		return -EBUSY;

	return 0;
}

static int open_low_hpage_areas(struct mm_struct *mm, u16 newareas)
{
	unsigned long i;

	BUILD_BUG_ON((sizeof(newareas)*8) != NUM_LOW_AREAS);
	BUILD_BUG_ON((sizeof(mm->context.low_htlb_areas)*8) != NUM_LOW_AREAS);

	newareas &= ~(mm->context.low_htlb_areas);
	if (! newareas)
		return 0; /* The segments we want are already open */

	for (i = 0; i < NUM_LOW_AREAS; i++)
		if ((1 << i) & newareas)
			if (prepare_low_area_for_htlb(mm, i) != 0)
				return -EBUSY;

	mm->context.low_htlb_areas |= newareas;

	/* update the paca copy of the context struct */
	get_paca()->context = mm->context;

	/* the context change must make it to memory before the flush,
	 * so that further SLB misses do the right thing. */
	mb();
	on_each_cpu(flush_low_segments, (void *)(unsigned long)newareas, 0, 1);

	return 0;
}

static int open_high_hpage_areas(struct mm_struct *mm, u16 newareas)
{
	unsigned long i;

	BUILD_BUG_ON((sizeof(newareas)*8) != NUM_HIGH_AREAS);
	BUILD_BUG_ON((sizeof(mm->context.high_htlb_areas)*8)
		     != NUM_HIGH_AREAS);

	newareas &= ~(mm->context.high_htlb_areas);
	if (! newareas)
		return 0; /* The areas we want are already open */

	for (i = 0; i < NUM_HIGH_AREAS; i++)
		if ((1 << i) & newareas)
			if (prepare_high_area_for_htlb(mm, i) != 0)
				return -EBUSY;

	mm->context.high_htlb_areas |= newareas;

	/* update the paca copy of the context struct */
	get_paca()->context = mm->context;

	/* the context change must make it to memory before the flush,
	 * so that further SLB misses do the right thing. */
	mb();
	on_each_cpu(flush_high_segments, (void *)(unsigned long)newareas, 0, 1);

	return 0;
}

int prepare_hugepage_range(unsigned long addr, unsigned long len)
{
	int err;

	if ( (addr+len) < addr )
		return -EINVAL;

	if ((addr + len) < 0x100000000UL)
		err = open_low_hpage_areas(current->mm,
					  LOW_ESID_MASK(addr, len));
	else
		err = open_high_hpage_areas(current->mm,
					    HTLB_AREA_MASK(addr, len));
	if (err) {
		printk(KERN_DEBUG "prepare_hugepage_range(%lx, %lx)"
		       " failed (lowmask: 0x%04hx, highmask: 0x%04hx)\n",
		       addr, len,
		       LOW_ESID_MASK(addr, len), HTLB_AREA_MASK(addr, len));
		return err;
	}

	return 0;
}

struct page *
follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
{
	pte_t *ptep;
	struct page *page;

	if (! in_hugepage_area(mm->context, address))
		return ERR_PTR(-EINVAL);

	ptep = huge_pte_offset(mm, address);
	page = pte_page(*ptep);
	if (page)
		page += (address % HPAGE_SIZE) / PAGE_SIZE;

	return page;
}

int pmd_huge(pmd_t pmd)
{
	return 0;
}

struct page *
follow_huge_pmd(struct mm_struct *mm, unsigned long address,
		pmd_t *pmd, int write)
{
	BUG();
	return NULL;
}

/* Because we have an exclusive hugepage region which lies within the
 * normal user address space, we have to take special measures to make
 * non-huge mmap()s evade the hugepage reserved regions. */
unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
				     unsigned long len, unsigned long pgoff,
				     unsigned long flags)
{
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma;
	unsigned long start_addr;

	if (len > TASK_SIZE)
		return -ENOMEM;

	if (addr) {
		addr = PAGE_ALIGN(addr);
		vma = find_vma(mm, addr);
		if (((TASK_SIZE - len) >= addr)
		    && (!vma || (addr+len) <= vma->vm_start)
		    && !is_hugepage_only_range(mm, addr,len))
			return addr;
	}
	if (len > mm->cached_hole_size) {
	        start_addr = addr = mm->free_area_cache;
	} else {
	        start_addr = addr = TASK_UNMAPPED_BASE;
	        mm->cached_hole_size = 0;
	}

full_search:
	vma = find_vma(mm, addr);
	while (TASK_SIZE - len >= addr) {
		BUG_ON(vma && (addr >= vma->vm_end));

		if (touches_hugepage_low_range(mm, addr, len)) {
			addr = ALIGN(addr+1, 1<<SID_SHIFT);
			vma = find_vma(mm, addr);
			continue;
		}
		if (touches_hugepage_high_range(mm, addr, len)) {
			addr = ALIGN(addr+1, 1UL<<HTLB_AREA_SHIFT);
			vma = find_vma(mm, addr);
			continue;
		}
		if (!vma || addr + len <= vma->vm_start) {
			/*
			 * Remember the place where we stopped the search:
			 */
			mm->free_area_cache = addr + len;
			return addr;
		}
		if (addr + mm->cached_hole_size < vma->vm_start)
		        mm->cached_hole_size = vma->vm_start - addr;
		addr = vma->vm_end;