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Differential D56518

vm: Add flags for unprotected allocations
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Authored by sarah.walker2_arm.com on Apr 20 2026, 1:16 PM.
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kib
alc
markj
andrew
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rGcd2512eaab5c: vm: Add flags for unprotected allocations
Summary

Unprotected allocations are intended to be accessible outside of the current
VM on systems such as Arm CCA.

Sponsored by: Arm Ltd

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rG FreeBSD src repository
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Event Timeline

sarah.walker2_arm.com created this revision.Apr 20 2026, 1:16 PM
Herald added a subscriber: imp. · View Herald TranscriptApr 20 2026, 1:16 PM
sarah.walker2_arm.com requested review of this revision.Apr 20 2026, 1:16 PM
Harbormaster completed remote builds in B72357: Diff 175892.Apr 20 2026, 1:16 PM
sarah.walker2_arm.com added a child revision: D56519: busdma_bounce: Allocate bounce buffers as unprotected.Apr 20 2026, 1:17 PM
andrew added reviewers: kib, alc, markj, andrew.Apr 20 2026, 1:23 PM
markj added a comment.Apr 20 2026, 2:28 PM

Why can't this flag be stored in the machine-dependent fields of the page, i.e., in some spare field of struct md_page?

sarah.walker2_arm.com updated this revision to Diff 175985.Apr 21 2026, 1:59 PM

Remove PG_UNPROTECTED flag

Harbormaster completed remote builds in B72418: Diff 175985.Apr 21 2026, 1:59 PM
sarah.walker2_arm.com added a comment.Apr 21 2026, 2:00 PM
In D56518#1293767, @markj wrote:

Why can't this flag be stored in the machine-dependent fields of the page, i.e., in some spare field of struct md_page?

I'm assuming you were referring to PG_UNPROTECTED? On further examination it's not required, so the latest change removes it.

markj added inline comments.Apr 21 2026, 2:53 PM
sys/vm/vm_page.h
537 ↗(On Diff #175985)

What's the purpose of VM_ALLOC_UNPROTECTED? vm_page_alloc_* don't do anything with it.

sarah.walker2_arm.com updated this revision to Diff 176091.Apr 22 2026, 10:19 AM

Remove VM_ALLOC_UNPROTECTED.

Harbormaster completed remote builds in B72433: Diff 176091.Apr 22 2026, 10:19 AM
sarah.walker2_arm.com added inline comments.Apr 22 2026, 10:20 AM
sys/vm/vm_page.h
537 ↗(On Diff #175985)

You are correct, VM_ALLOC_UNPROTECTED no long serves a purpose. Removed.

markj accepted this revision.Apr 22 2026, 1:05 PM

This seems fine, something similar will be needed on amd64 for, e.g., AMD SVE.

This revision is now accepted and ready to land.Apr 22 2026, 1:05 PM
alc added a comment.Thu, Apr 23, 5:07 AM

Just out of curiosity, where are the pmap changes?

andrew added a comment.Thu, Apr 23, 7:05 AM
In D56518#1295709, @alc wrote:

Just out of curiosity, where are the pmap changes?

They are part of D56520. To mark the mapping as unprotected we set a bit in the physical address. The firmware tells us which bit to set on boot.

My understanding is Intel and AMD have similar schemes on their equivalent to Arm CCA.

Closed by commit rGcd2512eaab5c: vm: Add flags for unprotected allocations (authored by sarah.walker2_arm.com, committed by andrew). · Explain WhyTue, May 12, 4:55 PM
This revision was automatically updated to reflect the committed changes.
andrew added a commit: rGcd2512eaab5c: vm: Add flags for unprotected allocations.

Revision Contents
Changeset List

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sys/
sys/
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vm/
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Diff 177687

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sys/sys/malloc.h

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sys/vm/pmap.h

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sys/vm/vm_kern.c

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