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Introduce pmap_clear(), which zeroes a page table entry, and use it, instead

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of pmap_load_clear(), in places where we don't care about the page table
entry's prior contents.

Eliminate an unnecessary pmap_load() from pmap_remove_all().  Instead, use
the value returned by the pmap_load_clear() on the very next line.  (In the
future, when we support "hardware dirty bit management", using the value
from the pmap_load() rather than the pmap_load_clear() would have actually
been an error because the dirty bit could potentially change between the
pmap_load() and the pmap_load_clear().)

A KASSERT() in pmap_enter(), which originated in the amd64 pmap, was meant
to check the value returned by the pmap_load_clear() on the previous line.
However, we were ignoring the value returned by the pmap_load_clear(), and
so the KASSERT() was not serving its intended purpose.  Use the value
returned by the pmap_load_clear() in the KASSERT().

MFC after:	2 weeks
This commit is contained in:
Alan Cox 2019-07-09 20:28:53 +00:00
parent a920680df5
commit d1dde35baa
1 changed files with 19 additions and 13 deletions
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32
sys/arm64/arm64/pmap.c
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@ -315,6 +315,7 @@ static __inline vm_page_t pmap_remove_pt_page(pmap_t pmap, vm_offset_t va);
* They need to be atomic as the System MMU may write to the table at
* the same time as the CPU.
*/
#define pmap_clear(table) atomic_store_64(table, 0)
#define pmap_load_store(table, entry) atomic_swap_64(table, entry)
#define pmap_set(table, mask) atomic_set_64(table, mask)
#define pmap_load_clear(table) atomic_swap_64(table, 0)
@ -1208,7 +1209,7 @@ pmap_kremove(vm_offset_t va)
KASSERT(pte != NULL, ("pmap_kremove: Invalid address"));
KASSERT(lvl == 3, ("pmap_kremove: Invalid pte level %d", lvl));
pmap_load_clear(pte);
pmap_clear(pte);
pmap_invalidate_page(kernel_pmap, va);
}
@ -1230,7 +1231,7 @@ pmap_kremove_device(vm_offset_t sva, vm_size_t size)
KASSERT(pte != NULL, ("Invalid page table, va: 0x%lx", va));
KASSERT(lvl == 3,
("Invalid device pagetable level: %d != 3", lvl));
pmap_load_clear(pte);
pmap_clear(pte);
va += PAGE_SIZE;
size -= PAGE_SIZE;
@ -1315,7 +1316,7 @@ pmap_qremove(vm_offset_t sva, int count)
KASSERT(lvl == 3,
("Invalid device pagetable level: %d != 3", lvl));
if (pte != NULL) {
pmap_load_clear(pte);
pmap_clear(pte);
}
va += PAGE_SIZE;
@ -1374,19 +1375,19 @@ _pmap_unwire_l3(pmap_t pmap, vm_offset_t va, vm_page_t m, struct spglist *free)
pd_entry_t *l0;
l0 = pmap_l0(pmap, va);
pmap_load_clear(l0);
pmap_clear(l0);
} else if (m->pindex >= NUL2E) {
/* l2 page */
pd_entry_t *l1;
l1 = pmap_l1(pmap, va);
pmap_load_clear(l1);
pmap_clear(l1);
} else {
/* l3 page */
pd_entry_t *l2;
l2 = pmap_l2(pmap, va);
pmap_load_clear(l2);
pmap_clear(l2);
}
pmap_resident_count_dec(pmap, 1);
if (m->pindex < NUL2E) {
@ -2760,8 +2761,7 @@ pmap_remove_all(vm_page_t m)
tpde = pmap_load(pde);
pte = pmap_l2_to_l3(pde, pv->pv_va);
tpte = pmap_load(pte);
pmap_load_clear(pte);
tpte = pmap_load_clear(pte);
pmap_invalidate_page(pmap, pv->pv_va);
if (tpte & ATTR_SW_WIRED)
pmap->pm_stats.wired_count--;
@ -2986,7 +2986,7 @@ pmap_update_entry(pmap_t pmap, pd_entry_t *pte, pd_entry_t newpte,
critical_enter();
/* Clear the old mapping */
pmap_load_clear(pte);
pmap_clear(pte);
pmap_invalidate_range_nopin(pmap, va, va + size);
/* Create the new mapping */
@ -3265,9 +3265,10 @@ pmap_enter(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot,
}
/*
* The physical page has changed.
* The physical page has changed. Temporarily invalidate
* the mapping.
*/
(void)pmap_load_clear(l3);
orig_l3 = pmap_load_clear(l3);
KASSERT((orig_l3 & ~ATTR_MASK) == opa,
("pmap_enter: unexpected pa update for %#lx", va));
if ((orig_l3 & ATTR_SW_MANAGED) != 0) {
@ -4282,7 +4283,12 @@ pmap_remove_pages(pmap_t pmap)
("pmap_remove_pages: bad pte %#jx",
(uintmax_t)tpte));
pmap_load_clear(pte);
/*
* Because this pmap is not active on other
* processors, the dirty bit cannot have
* changed state since we last loaded pte.
*/
pmap_clear(pte);
/*
* Update the vm_page_t clean/reference bits.
@ -5002,7 +5008,7 @@ pmap_unmapbios(vm_offset_t va, vm_size_t size)
("pmap_unmapbios: Invalid page entry, va: 0x%lx",
va_trunc));
l2 = pmap_l1_to_l2(pde, va_trunc);
pmap_load_clear(l2);
pmap_clear(l2);
if (block == (l2_blocks - 1))
break;