Date: Wed, 1 Sep 2021 13:31:10 GMT From: Mark Johnston <markj@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: 4b38880259e8 - stable/13 - Clear the accessed bit when copying a managed superpage mapping Message-ID: <202109011331.181DVAH6057106@gitrepo.freebsd.org>
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The branch stable/13 has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=4b38880259e81043978f4be27ef2289120c1b9d3 commit 4b38880259e81043978f4be27ef2289120c1b9d3 Author: Alan Cox <alc@FreeBSD.org> AuthorDate: 2021-07-13 07:30:43 +0000 Commit: Mark Johnston <markj@FreeBSD.org> CommitDate: 2021-09-01 13:29:01 +0000 Clear the accessed bit when copying a managed superpage mapping pmap_copy() is used to speculatively create mappings, so those mappings should not have their access bit preset. Reviewed by: kib, markj (cherry picked from commit 325ff9327459bc7307130675fa19367ff8b02310) --- sys/amd64/amd64/pmap.c | 17 ++++++++++++++++- sys/arm64/arm64/pmap.c | 18 ++++++++++++++++-- 2 files changed, 32 insertions(+), 3 deletions(-) diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c index 1d0b6aa0cce1..b920426e6996 100644 --- a/sys/amd64/amd64/pmap.c +++ b/sys/amd64/amd64/pmap.c @@ -7717,6 +7717,9 @@ pmap_copy(pmap_t dst_pmap, pmap_t src_pmap, vm_offset_t dst_addr, vm_size_t len, continue; if (srcptepaddr & PG_PS) { + /* + * We can only virtual copy whole superpages. + */ if ((addr & PDRMASK) != 0 || addr + NBPDR > end_addr) continue; pde = pmap_alloc_pde(dst_pmap, addr, &dst_pdpg, NULL); @@ -7725,7 +7728,19 @@ pmap_copy(pmap_t dst_pmap, pmap_t src_pmap, vm_offset_t dst_addr, vm_size_t len, if (*pde == 0 && ((srcptepaddr & PG_MANAGED) == 0 || pmap_pv_insert_pde(dst_pmap, addr, srcptepaddr, PMAP_ENTER_NORECLAIM, &lock))) { - *pde = srcptepaddr & ~PG_W; + /* + * We leave the dirty bit unchanged because + * managed read/write superpage mappings are + * required to be dirty. However, managed + * superpage mappings are not required to + * have their accessed bit set, so we clear + * it because we don't know if this mapping + * will be used. + */ + srcptepaddr &= ~PG_W; + if ((srcptepaddr & PG_MANAGED) != 0) + srcptepaddr &= ~PG_A; + *pde = srcptepaddr; pmap_resident_count_adj(dst_pmap, NBPDR / PAGE_SIZE); counter_u64_add(pmap_pde_mappings, 1); diff --git a/sys/arm64/arm64/pmap.c b/sys/arm64/arm64/pmap.c index a8216c6b4d7b..f0419beace37 100644 --- a/sys/arm64/arm64/pmap.c +++ b/sys/arm64/arm64/pmap.c @@ -4774,6 +4774,9 @@ pmap_copy(pmap_t dst_pmap, pmap_t src_pmap, vm_offset_t dst_addr, vm_size_t len, if (srcptepaddr == 0) continue; if ((srcptepaddr & ATTR_DESCR_MASK) == L2_BLOCK) { + /* + * We can only virtual copy whole superpages. + */ if ((addr & L2_OFFSET) != 0 || addr + L2_SIZE > end_addr) continue; @@ -4784,8 +4787,19 @@ 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_SW_WIRED; - pmap_store(l2, srcptepaddr & ~mask); + /* + * We leave the dirty bit unchanged because + * managed read/write superpage mappings are + * required to be dirty. However, managed + * superpage mappings are not required to + * have their accessed bit set, so we clear + * it because we don't know if this mapping + * will be used. + */ + srcptepaddr &= ~ATTR_SW_WIRED; + if ((srcptepaddr & ATTR_SW_MANAGED) != 0) + srcptepaddr &= ~ATTR_AF; + pmap_store(l2, srcptepaddr); pmap_resident_count_inc(dst_pmap, L2_SIZE / PAGE_SIZE); atomic_add_long(&pmap_l2_mappings, 1);
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