Achieve two goals at once: (1) Avoid an unnecessary broadcast TLB
invalidation in pmap_remove_all(). (2) Prevent an "invalid ASID" assertion failure in pmap_remove_all(). The architecture definition specifies that the TLB will not cache mappings that don't have the "AF" bit set, so pmap_remove_all() needn't issue a TLB invalidation for mappings that don't have the "AF" bit set. We allocate ASIDs lazily. Specifically, we don't allocate an ASID for a pmap until we are activating it. Now, consider what happens on a fork(). Before we activate the child's pmap, we use pmap_copy() to copy mappings from the parent's pmap to the child's. These new mappings have their "AF" bits cleared. Suppose that the page daemon decides to reclaim a page that underlies one of these new mappings. Previously, the pmap_invalidate_page() performed by pmap_remove_all() on a mapping in the child's pmap would fail an assertion because that pmap hasn't yet been assigned an ASID. However, we don't need to issue a TLB invalidation for such mappings because they can't possibly be cached in the TLB. Reported by: bob prohaska <fbsd@www.zefox.net> Reviewed by: markj MFC after: 1 week X-MFC-before: r354286 Differential Revision: https://reviews.freebsd.org/D22388
This commit is contained in:
parent
0857931660
commit
8a19cf92cf
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=354792
@ -2879,11 +2879,12 @@ pmap_remove_all(vm_page_t m)
|
||||
|
||||
pte = pmap_l2_to_l3(pde, pv->pv_va);
|
||||
tpte = pmap_load_clear(pte);
|
||||
pmap_invalidate_page(pmap, pv->pv_va);
|
||||
if (tpte & ATTR_SW_WIRED)
|
||||
pmap->pm_stats.wired_count--;
|
||||
if ((tpte & ATTR_AF) != 0)
|
||||
if ((tpte & ATTR_AF) != 0) {
|
||||
pmap_invalidate_page(pmap, pv->pv_va);
|
||||
vm_page_aflag_set(m, PGA_REFERENCED);
|
||||
}
|
||||
|
||||
/*
|
||||
* Update the vm_page_t clean and reference bits.
|
||||
|
Loading…
Reference in New Issue
Block a user