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Document new required MI behaviour of pmap_enter(9) for CoW.

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Reviewed by:	markj
MFC after:	3 days
Sponsored by:	The FreeBSD Foundation
Differential revision:	https://reviews.freebsd.org/D18568
This commit is contained in:
Konstantin Belousov 2018-12-16 01:51:38 +00:00
parent 3398cc6839
commit 6b5007c893
1 changed files with 9 additions and 1 deletions
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10
share/man/man9/pmap_enter.9
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@ -26,7 +26,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd February 16, 2018
.Dd December 16, 2018
.Dt PMAP_ENTER 9
.Os
.Sh NAME
@ -120,6 +120,14 @@ 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
is managed, the page must be busied by the caller