Document new required MI behaviour of pmap_enter(9) for CoW.
Reviewed by: markj MFC after: 3 days Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D18568
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2020-12-20 02:59:44 +00:00
svn path=/head/; revision=342144
@ -26,7 +26,7 @@
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.\"
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.\"
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.\" $FreeBSD$
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.\" $FreeBSD$
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.\"
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.\"
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.Dd February 16, 2018
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.Dd December 16, 2018
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.Dt PMAP_ENTER 9
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.Dt PMAP_ENTER 9
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.Os
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.Os
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.Sh NAME
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.Sh NAME
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@ -120,6 +120,14 @@ for destroyed mappings if the implementation can ensure
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that no other writeable managed mappings for the previously
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that no other writeable managed mappings for the previously
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mapped pages exist.
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mapped pages exist.
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.Pp
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.Pp
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If the request modifies an existing mapping to use a different physical
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page, an implementation of
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.Nm
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must invalidate the previous mapping before installing the new one.
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This ensures that all threads sharing the pmap keep a consistent
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view of the mapping, which is necessary for the correct handling
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of CoW (copy on write) faults.
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.Pp
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If the page
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If the page
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.Fa m
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.Fa m
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is managed, the page must be busied by the caller
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is managed, the page must be busied by the caller
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