Date: Wed, 20 Oct 2021 01:23:27 GMT From: Mark Johnston <markj@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 34fac29e9831 - main - amd64: Add comments to pmap_pinit_type() Message-ID: <202110200123.19K1NRrx095715@gitrepo.freebsd.org>
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The branch main has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=34fac29e98313fb0bfba0503e2e19e352b452516 commit 34fac29e98313fb0bfba0503e2e19e352b452516 Author: Mark Johnston <markj@FreeBSD.org> AuthorDate: 2021-10-20 00:29:18 +0000 Commit: Mark Johnston <markj@FreeBSD.org> CommitDate: 2021-10-20 01:22:57 +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 MFC after: 1 week Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D32528 --- 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 8d6379ab170c..66d7ac6669da 100644 --- a/sys/amd64/amd64/pmap.c +++ b/sys/amd64/amd64/pmap.c @@ -4345,7 +4345,9 @@ 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); @@ -4377,6 +4379,10 @@ 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(
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