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Implement pmap_copy() for ARMv6/v7.

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Copy the given range of mappings from the source map to the
destination map, thereby reducing the number of VM faults on fork.

Submitted by:   Zbigniew Bodek <zbb@semihalf.com>
Sponsored by:   The FreeBSD Foundation, Semihalf
This commit is contained in:
Grzegorz Bernacki 2013-06-04 09:21:18 +00:00
parent 580dbd6574
commit df8c5665ac
1 changed files with 120 additions and 0 deletions
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120
sys/arm/arm/pmap-v6.c
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@ -2966,6 +2966,126 @@ void
pmap_copy(pmap_t dst_pmap, pmap_t src_pmap, vm_offset_t dst_addr,
vm_size_t len, vm_offset_t src_addr)
{
struct l2_bucket *l2b_src, *l2b_dst;
struct pv_entry *pve;
vm_offset_t addr;
vm_offset_t end_addr;
vm_offset_t next_bucket;
u_int flags;
boolean_t l2b_alloc;
CTR4(KTR_PMAP, "%s: VA = 0x%08x, len = 0x%08x. Will %s\n", __func__,
src_addr, len, (dst_addr != src_addr) ? "exit" : "copy");
if (dst_addr != src_addr)
return;
rw_wlock(&pvh_global_lock);
if (dst_pmap < src_pmap) {
PMAP_LOCK(dst_pmap);
PMAP_LOCK(src_pmap);
} else {
PMAP_LOCK(src_pmap);
PMAP_LOCK(dst_pmap);
}
end_addr = src_addr + len;
addr = src_addr;
/*
* Iterate through all used l2_buckets in a given range.
*/
while (addr < end_addr) {
pt_entry_t *src_ptep, *dst_ptep;
pt_entry_t src_pte;
next_bucket = L2_NEXT_BUCKET(addr);
/*
* If the next bucket VA is out of the
* copy range then set it to end_addr in order
* to copy all mappings until the given limit.
*/
if (next_bucket > end_addr)
next_bucket = end_addr;
l2b_src = pmap_get_l2_bucket(src_pmap, addr);
if (l2b_src == NULL) {
addr = next_bucket;
continue;
}
src_ptep = &l2b_src->l2b_kva[l2pte_index(addr)];
while (addr < next_bucket) {
vm_page_t srcmpte;
src_pte = *src_ptep;
srcmpte = PHYS_TO_VM_PAGE(l2pte_pa(src_pte));
/*
* We only virtual copy managed pages
*/
if (srcmpte && (srcmpte->oflags & VPO_UNMANAGED) == 0) {
l2b_alloc = FALSE;
l2b_dst = pmap_get_l2_bucket(dst_pmap, addr);
/*
* Check if the allocation of another
* l2_bucket is necessary.
*/
if (l2b_dst == NULL) {
l2b_dst = pmap_alloc_l2_bucket(dst_pmap,
addr);
l2b_alloc = TRUE;
}
if (l2b_dst == NULL)
goto out;
dst_ptep = &l2b_dst->l2b_kva[l2pte_index(addr)];
if (*dst_ptep == 0 &&
(pve = pmap_get_pv_entry(dst_pmap, TRUE))) {
/*
* Check whether the source mapping is
* writable and set the proper flag
* for a copied mapping so that right
* permissions could be set on the
* access fault.
*/
flags = 0;
if ((src_pte & L2_APX) == 0)
flags = PVF_WRITE;
pmap_enter_pv(srcmpte, pve, dst_pmap,
addr, flags);
/*
* Clear the modified and
* accessed (referenced) flags
* and don't set the wired flag
* during the copy.
*/
*dst_ptep = src_pte;
*dst_ptep &= ~L2_S_REF;
*dst_ptep |= L2_APX;
/*
* Update stats
*/
l2b_dst->l2b_occupancy++;
dst_pmap->pm_stats.resident_count++;
} else {
/*
* If the l2_bucket was acquired as
* a result of allocation then free it.
*/
if (l2b_alloc)
pmap_free_l2_bucket(dst_pmap,
l2b_dst, 1);
goto out;
}
}
addr += PAGE_SIZE;
src_ptep++;
}
}
out:
rw_wunlock(&pvh_global_lock);
PMAP_UNLOCK(src_pmap);
PMAP_UNLOCK(dst_pmap);
}