Add missing pmap dsb instructions
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Authored by andrew on Feb 7 2019, 9:53 AM.

Details

Reviewers

jchandra
manu

Group Reviewers

arm64

Commits

rS352396: MFC r343876:
rS343876: Add missing data barriers after storeing a new valid pagetable entry.
rS343875: Add a missing data barrier to the start of arm64_tlb_flushID.

Summary

We need them in arm64_tlb_flushID when clearing the TLB and after pagetable
stores when moving from an invalid to valid entry. The latter don't call
any of the pmap_invalidate_* functions.

Diff Detail

Repository

rS FreeBSD src repository - subversion

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Unit

Tests Not Applicable

Event Timeline

andrew created this revision.Feb 7 2019, 9:53 AM

Herald added a reviewer: manu. · View Herald TranscriptFeb 7 2019, 9:53 AM

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Harbormaster completed remote builds in B22371: Diff 53640.Feb 7 2019, 9:53 AM

This fixes the failure on ThunderX2 when INVARIANTS are turned off. The failure was:

panic: vm_fault_hold: fault on nofault entry, addr: 0xffff000040c11000
cpuid = 0
time = 1

Tested with overnight 'make -j 224 buildworld' without failures.
This is more of a 'Tested by' - I don't have enough background here to do a full review. My understanding of ARM spec is you need a dsb after a update of valid pte/pde, before access to the page. ThunderX2 has full out of order execution with weakly ordered loads and stores - so the failure above points to a missing barrier.

This revision is now accepted and ready to land.Feb 7 2019, 6:52 PM

In D19097#408644, @jchandra wrote:

Tested with overnight 'make -j 224 buildworld' without failures.

How long does that take?

This is more of a 'Tested by' - I don't have enough background here to do a full review. My understanding of ARM spec is you need a dsb after a update of valid pte/pde, before access to the page. ThunderX2 has full out of order execution with weakly ordered loads and stores - so the failure above points to a missing barrier.

We need one whenever we create a valid page. In many cases there was one because of the call to pmap_invalidate_* functions, however a few were missed.

Closed by commit rS343875: Add a missing data barrier to the start of arm64_tlb_flushID. (authored by andrew). · Explain WhyFeb 7 2019, 8:50 PM

This revision was automatically updated to reflect the committed changes.

Herald added a subscriber: imp. · View Herald TranscriptFeb 7 2019, 8:50 PM

andrew reopened this revision.Feb 7 2019, 8:51 PM

This revision was not accepted when it landed; it landed in state Needs Review.Feb 7 2019, 8:59 PM

Closed by commit rS343876: Add missing data barriers after storeing a new valid pagetable entry. (authored by andrew). · Explain Why

This revision was automatically updated to reflect the committed changes.

In D19097#408663, @andrew wrote:

In D19097#408644, @jchandra wrote:

Tested with overnight 'make -j 224 buildworld' without failures.

How long does that take?