Refine the fix from r312954; add a PG_PROMOTED flag for marking promoted PDEs
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Authored by alc on Feb 18 2017, 7:39 PM.

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kib
markj

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rS314310: Refine the fix from r312954. Specifically, add a new PDE-only flag,

Summary

Mark promoted PDEs with the new PG_PROMOTED flag so that the amd64 pmap knows whether lingering 4K page mappings need to be flushed on a PDE change that restricts or destroys the mapping. This allows the amd64 pmap to avoid unnecessary and costly range invalidations.

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rS FreeBSD src repository - subversion

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alc updated this revision to Diff 25361.Feb 18 2017, 7:39 PM

alc retitled this revision from to Refine the fix from r312954; add a PG_PROMOTED flag for marking promoted PDEs.

alc updated this object.

alc edited the test plan for this revision. (Show Details)

alc added reviewers: kib, markj.

kib accepted this revision.Feb 18 2017, 9:03 PM

kib edited edge metadata.

This revision is now accepted and ready to land.Feb 18 2017, 9:03 PM

markj accepted this revision.Feb 18 2017, 10:42 PM

markj edited edge metadata.

markj added inline comments.

amd64/amd64/pmap.c
1858 ↗	(On Diff #25361)	Is it worth asserting !workaround_erratum383 if PG_PROMOTED is set?

alc added inline comments.Feb 18 2017, 11:26 PM

amd64/amd64/pmap.c
1858 ↗	(On Diff #25361)	There are 2M page mappings that are not the result of promotion, e.g., pmap_enter_pde() and an upcoming patch that adds support for "psind == 1" to pmap_enter(). That said, the bug fixed by r312954 involved PG_G mappings and currently pmap_enter_pde() never creates PG_G mappings, so we would not yet call this function on anything but a promoted mapping. However, that is going to change before too long.