Refine the fix from r312954; add a PG_PROMOTED flag for marking promoted PDEs
ClosedPublic
Actions

Authored by alc on Feb 18 2017, 7:39 PM.

Details

Reviewers

kib
markj

Commits

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.

Diff Detail

Lint

Lint Skipped

Unit

Tests Skipped

Event Timeline

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	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	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.