The branch main has been updated by alc:
URL:
https://cgit.FreeBSD.org/src/commit/?id=fb32ba6aa44dc86e70ad06b44f93a9709e78f3d1
commit fb32ba6aa44dc86e70ad06b44f93a9709e78f3d1
Author: Alan Cox <a...@freebsd.org>
AuthorDate: 2024-07-05 18:20:01 +0000
Commit: Alan Cox <a...@freebsd.org>
CommitDate: 2024-07-06 20:48:10 +0000
amd64/arm64: Eliminate unnecessary demotions in pmap_protect()
In pmap_protect(), when the mapping isn't changing, we don't need to
perform a superpage demotion, even though the requested change doesn't
cover the entire superpage.
Reviewed by: kib
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D45886
---
sys/amd64/amd64/pmap.c | 21 +++++++++++++++++----
sys/arm64/arm64/pmap.c | 3 ++-
2 files changed, 19 insertions(+), 5 deletions(-)
diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
index 57943e815b5b..2bcf671be243 100644
--- a/sys/amd64/amd64/pmap.c
+++ b/sys/amd64/amd64/pmap.c
@@ -6796,8 +6796,7 @@ retry_pdpe:
*/
if ((ptpaddr & PG_PS) != 0) {
/*
- * Are we protecting the entire large page? If not,
- * demote the mapping and fall through.
+ * Are we protecting the entire large page?
*/
if (sva + NBPDR == va_next && eva >= va_next) {
/*
@@ -6807,9 +6806,23 @@ retry_pdpe:
if (pmap_protect_pde(pmap, pde, sva, prot))
anychanged = true;
continue;
- } else if (!pmap_demote_pde(pmap, pde, sva)) {
+ }
+
+ /*
+ * Does the large page mapping need to change? If so,
+ * demote it and fall through.
+ */
+ pbits = ptpaddr;
+ if ((prot & VM_PROT_WRITE) == 0)
+ pbits &= ~(PG_RW | PG_M);
+ if ((prot & VM_PROT_EXECUTE) == 0)
+ pbits |= pg_nx;
+ if (ptpaddr == pbits || !pmap_demote_pde(pmap, pde,
+ sva)) {
/*
- * The large page mapping was destroyed.
+ * Either the large page mapping doesn't need
+ * to change, or it was destroyed during
+ * demotion.
*/
continue;
}
diff --git a/sys/arm64/arm64/pmap.c b/sys/arm64/arm64/pmap.c
index a9cb8c7fe468..29552f722aa4 100644
--- a/sys/arm64/arm64/pmap.c
+++ b/sys/arm64/arm64/pmap.c
@@ -4373,7 +4373,8 @@ pmap_mask_set_locked(pmap_t pmap, vm_offset_t sva,
vm_offset_t eva, pt_entry_t m
if (sva + L2_SIZE == va_next && eva >= va_next) {
pmap_protect_l2(pmap, l2, sva, mask, nbits);
continue;
- } else if (pmap_demote_l2(pmap, l2, sva) == NULL)
+ } else if ((pmap_load(l2) & mask) == nbits ||
+ pmap_demote_l2(pmap, l2, sva) == NULL)
continue;
}
KASSERT((pmap_load(l2) & ATTR_DESCR_MASK) == L2_TABLE,
