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Differential D31958

vm_phys: do not ignore phys_avail[] segments that do not fit completely into vm_phys segments
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Authored by kib on Sep 14 2021, 12:34 PM.
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cy
madpilot

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alc
markj
andrew
madpilot
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rG181bfb42fd01: vm_phys: do not ignore phys_avail[] segments that do not fit completely into…
Summary

If phys_avail[] segment only intersect with some vm_phys segment, add pages from it to the free list that belong to the given vm_phys_seg, instead of dropping them.

The vm_phys segments are generally result of subdivision of phys_avail segments, for instance DMA32 or LOWMEM boundaries split them. On amd64, after UEFI in-place kernel activation (copy_staging disable) was enabled, we typically have a large phys_avail[] segment below 4G which crosses LOWMEM (1M) boundary. With the current way of requiring phys_avail[] fully fit into vm_phys_seg, this memory was ignored.

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Event Timeline

kib requested review of this revision.Sep 14 2021, 12:34 PM
kib created this revision.
madpilot accepted this revision.Sep 14 2021, 1:42 PM

I confirm that with this patch applied my system is now able to see all its RAM.

Thank you!

This revision is now accepted and ready to land.Sep 14 2021, 1:42 PM
markj added inline comments.Sep 14 2021, 2:49 PM
sys/vm/vm_page.c
776

This comment no longer holds.

kib updated this revision to Diff 95152.Sep 14 2021, 3:01 PM
kib marked an inline comment as done.

Update comment.

This revision now requires review to proceed.Sep 14 2021, 3:01 PM
cy added a subscriber: cy.Sep 14 2021, 5:45 PM
alc added inline comments.Sep 15 2021, 6:44 AM
sys/vm/vm_page.c
774–776
kib updated this revision to Diff 95189.Sep 15 2021, 7:30 AM
kib marked an inline comment as done.

Reword comment, by Alan.

markj added inline comments.Sep 15 2021, 1:38 PM
sys/vm/vm_page.c
798–799

Isn't it possible for some of the excluded range of the phys_seg to be present in a different phys_avail[] region?

kib added inline comments.Sep 15 2021, 1:43 PM
sys/vm/vm_page.c
798–799

Do you mean that this break statement should be removed?

798–799

And the condition seg->start< phys_avail[i] replaced by seg->end < phys_avail[i] perhaps

kib updated this revision to Diff 95194.Sep 15 2021, 2:00 PM

Walk over all phys_avail[] segments which overlap with our vm_phys_seg when gathering the vm_phys_seg' pages

markj accepted this revision.Sep 15 2021, 8:02 PM
This revision is now accepted and ready to land.Sep 15 2021, 8:02 PM
Closed by commit rG181bfb42fd01: vm_phys: do not ignore phys_avail[] segments that do not fit completely into… (authored by kib). · Explain WhySep 16 2021, 5:11 PM
This revision was automatically updated to reflect the committed changes.
kib added a commit: rG181bfb42fd01: vm_phys: do not ignore phys_avail[] segments that do not fit completely into….
alc added inline comments.Sep 17 2021, 6:12 PM
sys/vm/vm_page.c
778–779

Why not test for equality here? It seems pointless to allow execution to continue if they are equal.

783

Shouldn't this be startp - seg->start?

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vm/
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Diff 95194

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sys/vm/vm_page.c

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