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author | alc <alc@FreeBSD.org> | 2014-07-06 17:42:38 +0000 |
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committer | alc <alc@FreeBSD.org> | 2014-07-06 17:42:38 +0000 |
commit | d74e85dbb9aba51f1ffc63a0ebae250559a8fcd9 (patch) | |
tree | a294db7e9041f651c7a421baf7d2bc56d5447086 /sys/i386/xen | |
parent | 3437bf817836057606a700b02d68b0ed46582823 (diff) | |
download | FreeBSD-src-d74e85dbb9aba51f1ffc63a0ebae250559a8fcd9.zip FreeBSD-src-d74e85dbb9aba51f1ffc63a0ebae250559a8fcd9.tar.gz |
Introduce pmap_unwire(). It will replace pmap_change_wiring(). There are
several reasons for this change:
pmap_change_wiring() has never (in my memory) been used to set the wired
attribute on a virtual page. We have always used pmap_enter() to do that.
Moreover, it is not really safe to use pmap_change_wiring() to set the wired
attribute on a virtual page. The description of pmap_change_wiring() says
that it assumes the existence of a mapping in the pmap. However, non-wired
mappings may be reclaimed by the pmap at any time. (See pmap_collect().)
Many implementations of pmap_change_wiring() will crash if the mapping does
not exist.
pmap_unwire() accepts a range of virtual addresses, whereas
pmap_change_wiring() acts upon a single virtual page. Since we are
typically unwiring a range of virtual addresses, pmap_unwire() will be more
efficient. Moreover, pmap_unwire() allows us to unwire superpage mappings.
Previously, we were forced to demote the superpage mapping, because
pmap_change_wiring() only allowed us to express the unwiring of a single
base page mapping at a time. This added to the overhead of unwiring for
large ranges of addresses, including the implicit unwiring that occurs at
process termination.
Implementations for arm and powerpc will follow.
Discussed with: jeff, marcel
Reviewed by: kib
Sponsored by: EMC / Isilon Storage Division
Diffstat (limited to 'sys/i386/xen')
-rw-r--r-- | sys/i386/xen/pmap.c | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/sys/i386/xen/pmap.c b/sys/i386/xen/pmap.c index fdc64bc..54ee3a6 100644 --- a/sys/i386/xen/pmap.c +++ b/sys/i386/xen/pmap.c @@ -3199,6 +3199,57 @@ pmap_change_wiring(pmap_t pmap, vm_offset_t va, boolean_t wired) rw_wunlock(&pvh_global_lock); } +/* + * Clear the wired attribute from the mappings for the specified range of + * addresses in the given pmap. Every valid mapping within that range + * must have the wired attribute set. In contrast, invalid mappings + * cannot have the wired attribute set, so they are ignored. + * + * The wired attribute of the page table entry is not a hardware feature, + * so there is no need to invalidate any TLB entries. + */ +void +pmap_unwire(pmap_t pmap, vm_offset_t sva, vm_offset_t eva) +{ + vm_offset_t pdnxt; + pd_entry_t *pde; + pt_entry_t *pte; + + CTR3(KTR_PMAP, "pmap_unwire: pmap=%p sva=0x%x eva=0x%x", pmap, sva, + eva); + rw_wlock(&pvh_global_lock); + sched_pin(); + PMAP_LOCK(pmap); + for (; sva < eva; sva = pdnxt) { + pdnxt = (sva + NBPDR) & ~PDRMASK; + if (pdnxt < sva) + pdnxt = eva; + pde = pmap_pde(pmap, sva); + if ((*pde & PG_V) == 0) + continue; + if ((*pde & PG_PS) != 0) + panic("pmap_unwire: unexpected PG_PS in pde %#jx", + (uintmax_t)*pde); + if (pdnxt > eva) + pdnxt = eva; + for (pte = pmap_pte_quick(pmap, sva); sva != pdnxt; pte++, + sva += PAGE_SIZE) { + if ((*pte & PG_V) == 0) + continue; + if ((*pte & PG_W) == 0) + panic("pmap_unwire: pte %#jx is missing PG_W", + (uintmax_t)*pte); + PT_SET_VA_MA(pte, *pte & ~PG_W, FALSE); + pmap->pm_stats.wired_count--; + } + } + if (*PMAP1) + PT_CLEAR_VA(PMAP1, FALSE); + PT_UPDATES_FLUSH(); + sched_unpin(); + rw_wunlock(&pvh_global_lock); + PMAP_UNLOCK(pmap); +} /* |