The branch main has been updated by markj:
URL:
https://cgit.FreeBSD.org/src/commit/?id=4e4035ef1fb5e2f9da6b658ffae8a54862b4d018
commit 4e4035ef1fb5e2f9da6b658ffae8a54862b4d018
Author: Mark Johnston <ma...@freebsd.org>
AuthorDate: 2021-06-06 20:40:45 +0000
Commit: Mark Johnston <ma...@freebsd.org>
CommitDate: 2021-06-06 20:44:46 +0000
arm64: Fix pmap_copy()'s handling of 2MB mappings
When copying mappings from parent to child, we clear the accessed and
dirty bits. This is done for both 4KB and 2MB PTEs. However,
pmap_demote_l2() asserts that writable superpages must be dirty. This
is to avoid races with the MMU setting the dirty bit during promotion
and demotion. pmap_copy() can create clean, writable superpage
mappings, so it violates this assertion.
Modify pmap_copy() to preserve the accessed and dirty bits when copying
2MB mappings, like we do on amd64.
Fixes: ca2cae0b4dd
Reported by: Jenkins via mhorne
Reviewed by: alc, kib
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D30643
---
sys/arm64/arm64/pmap.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/sys/arm64/arm64/pmap.c b/sys/arm64/arm64/pmap.c
index c26c3d8fce17..ffc83be852bd 100644
--- a/sys/arm64/arm64/pmap.c
+++ b/sys/arm64/arm64/pmap.c
@@ -4573,11 +4573,8 @@ pmap_copy(pmap_t dst_pmap, pmap_t src_pmap, vm_offset_t
dst_addr, vm_size_t len,
((srcptepaddr & ATTR_SW_MANAGED) == 0 ||
pmap_pv_insert_l2(dst_pmap, addr, srcptepaddr,
PMAP_ENTER_NORECLAIM, &lock))) {
- mask = ATTR_AF | ATTR_SW_WIRED;
- nbits = 0;
- if ((srcptepaddr & ATTR_SW_DBM) != 0)
- nbits |= ATTR_S1_AP_RW_BIT;
- pmap_store(l2, (srcptepaddr & ~mask) | nbits);
+ mask = ATTR_SW_WIRED;
+ pmap_store(l2, srcptepaddr & ~mask);
pmap_resident_count_inc(dst_pmap, L2_SIZE /
PAGE_SIZE);
atomic_add_long(&pmap_l2_mappings, 1);
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