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Differential D15675

Account for dmap limit when selecting the pages for the bootstrap pagetables.
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Authored by kib on Jun 6 2018, 2:44 PM.
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royger
grembo
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rS334799: Account for dmap limit when selecting the pages for the bootstrap
Summary

physmap[] can be inconsistent with the physical memory limit due to buggy bios, or to the hw.physmem tunable. Since bootstrap pagetables are initialized by accesses through the DMAP, we must ensure that DMAP really cover the selected pages. This is only relevant when machine has less than 4G RAM and buggy BIOS, which is the combination on Acer Chromebook 720.

An alternative could be to always cover 4G for DMAP, but this change seems to be simpler.

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rS FreeBSD src repository - subversion
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Event Timeline

kib created this revision.Jun 6 2018, 2:44 PM
Herald added a subscriber: imp. · View Herald TranscriptJun 6 2018, 2:44 PM
Harbormaster completed remote builds in B17033: Diff 43361.Jun 6 2018, 2:45 PM
kib updated this revision to Diff 43364.Jun 6 2018, 3:24 PM

Rework the change as discussed with royger.

Michael, please retest.

royger accepted this revision.Jun 6 2018, 3:31 PM

LGTM, just one nit.

sys/amd64/amd64/mp_machdep.c
125 ↗(On Diff #43364)

I would use 'physmap[i + 1] > Maxmem', to make sure that all the pages used to build the page tables are below Maxmem, not just the initial one.

This revision is now accepted and ready to land.Jun 6 2018, 3:31 PM
kib updated this revision to Diff 43365.Jun 6 2018, 3:35 PM

Fix bug.

This revision now requires review to proceed.Jun 6 2018, 3:35 PM
royger accepted this revision.Jun 6 2018, 3:50 PM
This revision is now accepted and ready to land.Jun 6 2018, 3:50 PM
grembo added a comment.Jun 6 2018, 11:09 PM

@kib Updated by tree to r334733 and applied the patch, it's working as expected, thanks!

grembo accepted this revision.Jun 6 2018, 11:10 PM
Closed by commit rS334799: Account for dmap limit when selecting the pages for the bootstrap (authored by kib). · Explain WhyJun 7 2018, 5:04 PM
This revision was automatically updated to reflect the committed changes.

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head/
sys/
amd64/
amd64/
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14 lines

Diff 43425

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head/sys/amd64/amd64/machdep.c

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head/sys/amd64/amd64/mp_machdep.c

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