Date: Wed, 19 Dec 2018 03:23:23 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-11@freebsd.org Subject: svn commit: r342213 - stable/11/share/man/man9 Message-ID: <201812190323.wBJ3NNRA058620@repo.freebsd.org>
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Author: kib Date: Wed Dec 19 03:23:23 2018 New Revision: 342213 URL: https://svnweb.freebsd.org/changeset/base/342213 Log: MFC r342144: Document new required MI behaviour of pmap_enter(9) for CoW. Modified: stable/11/share/man/man9/pmap_enter.9 Directory Properties: stable/11/ (props changed) Modified: stable/11/share/man/man9/pmap_enter.9 ============================================================================== --- stable/11/share/man/man9/pmap_enter.9 Wed Dec 19 03:21:49 2018 (r342212) +++ stable/11/share/man/man9/pmap_enter.9 Wed Dec 19 03:23:23 2018 (r342213) @@ -26,7 +26,7 @@ .\" .\" $FreeBSD$ .\" -.Dd February 16, 2018 +.Dd December 16, 2018 .Dt PMAP_ENTER 9 .Os .Sh NAME @@ -119,6 +119,14 @@ It is advised to clear for destroyed mappings if the implementation can ensure that no other writeable managed mappings for the previously mapped pages exist. +.Pp +If the request modifies an existing mapping to use a different physical +page, an implementation of +.Nm +must invalidate the previous mapping before installing the new one. +This ensures that all threads sharing the pmap keep a consistent +view of the mapping, which is necessary for the correct handling +of CoW (copy on write) faults. .Pp If the page .Fa m
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