git: 0fcf472fd583 - stable/13 - amd64: Add comments to pmap_pinit_type()
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Date: Wed, 03 Nov 2021 17:54:04 UTC
The branch stable/13 has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=0fcf472fd583c51d5d583305c10ba1430a378ba1 commit 0fcf472fd583c51d5d583305c10ba1430a378ba1 Author: Mark Johnston <markj@FreeBSD.org> AuthorDate: 2021-10-20 00:29:18 +0000 Commit: Mark Johnston <markj@FreeBSD.org> CommitDate: 2021-11-03 17:41:55 +0000 amd64: Add comments to pmap_pinit_type() ... explaining why we don't pass the pmap pointer to pmap_alloc_pt_page(). Reported by: alc Reviewed by: alc, kib Sponsored by: The FreeBSD Foundation (cherry picked from commit 34fac29e98313fb0bfba0503e2e19e352b452516) --- sys/amd64/amd64/pmap.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c index 19219e4676cc..d7954b9444b5 100644 --- a/sys/amd64/amd64/pmap.c +++ b/sys/amd64/amd64/pmap.c @@ -4293,7 +4293,9 @@ pmap_pinit_type(pmap_t pmap, enum pmap_type pm_type, int flags) int i; /* - * allocate the page directory page + * Allocate the page directory page. Pass NULL instead of a pointer to + * the pmap here to avoid recording this page in the resident count, as + * optimizations in pmap_remove() depend on this. */ pmltop_pg = pmap_alloc_pt_page(NULL, 0, VM_ALLOC_WIRED | VM_ALLOC_ZERO | VM_ALLOC_WAITOK); @@ -4325,6 +4327,10 @@ pmap_pinit_type(pmap_t pmap, enum pmap_type pm_type, int flags) else pmap_pinit_pml4(pmltop_pg); if ((curproc->p_md.md_flags & P_MD_KPTI) != 0) { + /* + * As with pmltop_pg, pass NULL instead of a pointer to + * the pmap to ensure that the PTI page isn't counted. + */ pmltop_pgu = pmap_alloc_pt_page(NULL, 0, VM_ALLOC_WIRED | VM_ALLOC_WAITOK); pmap->pm_pmltopu = (pml4_entry_t *)PHYS_TO_DMAP(