riscv: Construct an identity map in locore.S
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Authored by mhorne on May 23 2024, 7:52 PM.

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markj
br
jrtc27
jhb

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riscv

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rGbfb857546984: riscv: Construct an identity map in locore.S

Summary

This is useful for two reasons. Within this change, it allows the
early DTB mapping to be eliminated, as we can now just dereference the
physical address provided by FW and copy the DTB contents into KVA.

It will also aid in an upcoming change.

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Repository

rG FreeBSD src repository

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Buildable 58031
Build 54919: arc lint + arc unit

Event Timeline

mhorne created this revision.May 23 2024, 7:52 PM

Herald added a subscriber: imp. · View Herald TranscriptMay 23 2024, 7:52 PM

mhorne requested review of this revision.May 23 2024, 7:52 PM

Harbormaster completed remote builds in B57878: Diff 139007.May 23 2024, 7:52 PM

mhorne added a child revision: D45325: riscv: adjust physmem reservation.May 23 2024, 7:52 PM

markj added inline comments.May 27 2024, 1:51 PM

sys/riscv/riscv/locore.S
124	A more elaborate comment would be helpful: When is this map used? Is the mapping temporary? If so, when is it removed? What does it cover?
sys/riscv/riscv/pmap.c
698	Do you still need this fence? It looks like belongs in pmap_bootstrap_l3().

markj added inline comments.May 27 2024, 2:11 PM

sys/riscv/riscv/locore.S
124	I see that you do this in a follow-up commit.

mhorne marked an inline comment as done.May 27 2024, 2:50 PM

mhorne added inline comments.

sys/riscv/riscv/pmap.c
698	Agreed, it is odd here, but precedes the addition of the code I am removing. It would be better to check the usage of this fence in the later reworking of `pmap_bootstrap()`, D45327. This change is essentially part of that rework, and although I separated it for the sake of review, the split is imperfect.