The branch main has been updated by alc:
URL:
https://cgit.FreeBSD.org/src/commit/?id=3687797618b6c978ad733bd206a623e5df47dbe3
commit 3687797618b6c978ad733bd206a623e5df47dbe3
Author: Alan Cox <a...@freebsd.org>
AuthorDate: 2021-07-24 08:50:27 +0000
Commit: Alan Cox <a...@freebsd.org>
CommitDate: 2021-07-24 18:06:47 +0000
amd64: Don't repeat unnecessary tests when cmpset fails
When a cmpset for removing the PG_RW bit in pmap_promote_pde() fails,
there is no need to repeat the alignment, PG_A, and PG_V tests just to
reload the PTE's value. The only bit that we need be concerned with at
this point is PG_M. Use fcmpset instead.
MFC after: 1 week
---
sys/amd64/amd64/pmap.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
index aea4394ebcc0..47315c560831 100644
--- a/sys/amd64/amd64/pmap.c
+++ b/sys/amd64/amd64/pmap.c
@@ -6615,7 +6615,6 @@ pmap_promote_pde(pmap_t pmap, pd_entry_t *pde,
vm_offset_t va,
* within a 2MB page.
*/
firstpte = (pt_entry_t *)PHYS_TO_DMAP(*pde & PG_FRAME);
-setpde:
newpde = *firstpte;
if ((newpde & ((PG_FRAME & PDRMASK) | PG_A | PG_V)) != (PG_A | PG_V) ||
!pmap_allow_2m_x_page(pmap, pmap_pde_ept_executable(pmap,
@@ -6625,12 +6624,13 @@ setpde:
" in pmap %p", va, pmap);
return;
}
+setpde:
if ((newpde & (PG_M | PG_RW)) == PG_RW) {
/*
* When PG_M is already clear, PG_RW can be cleared without
* a TLB invalidation.
*/
- if (!atomic_cmpset_long(firstpte, newpde, newpde & ~PG_RW))
+ if (!atomic_fcmpset_long(firstpte, &newpde, newpde & ~PG_RW))
goto setpde;
newpde &= ~PG_RW;
}
@@ -6642,7 +6642,6 @@ setpde:
*/
pa = (newpde & (PG_PS_FRAME | PG_A | PG_V)) + NBPDR - PAGE_SIZE;
for (pte = firstpte + NPTEPG - 1; pte > firstpte; pte--) {
-setpte:
oldpte = *pte;
if ((oldpte & (PG_FRAME | PG_A | PG_V)) != pa) {
counter_u64_add(pmap_pde_p_failures, 1);
@@ -6650,12 +6649,13 @@ setpte:
" in pmap %p", va, pmap);
return;
}
+setpte:
if ((oldpte & (PG_M | PG_RW)) == PG_RW) {
/*
* When PG_M is already clear, PG_RW can be cleared
* without a TLB invalidation.
*/
- if (!atomic_cmpset_long(pte, oldpte, oldpte & ~PG_RW))
+ if (!atomic_fcmpset_long(pte, &oldpte, oldpte & ~PG_RW))
goto setpte;
oldpte &= ~PG_RW;
CTR2(KTR_PMAP, "pmap_promote_pde: protect for va %#lx"
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