arm64 pmap: introduce PHYS_TO_PTE macro
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Authored by zachary.leaf_arm.com on Apr 26 2023, 12:25 PM.

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alc
manu
kib
markj

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arm64

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rG012ea67d2d17: arm64 pmap: introduce PHYS_TO_PTE macro

Summary

Introduce macro for PHYS_TO_PTE, setting the groundwork for future
support of various Arm VMSA extensions.

For extensions such as 52-bit VA/PA (FEAT_LPA2), the representation of
an address between a PTE and PA are not equivalent. This macro will
allow converting between the different representations.

Currently PHYS_TO_PTE is a NOP. Replace all instances where we go from
PA to PTE with new PHYS_TO_PTE macro.

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rG FreeBSD src repository

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Buildable 51313
Build 48204: arc lint + arc unit

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zachary.leaf_arm.com created this revision.Apr 26 2023, 12:25 PM

Herald added a reviewer: manu. · View Herald TranscriptApr 26 2023, 12:25 PM

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zachary.leaf_arm.com requested review of this revision.Apr 26 2023, 12:25 PM

Harbormaster completed remote builds in B51206: Diff 121074.Apr 26 2023, 12:25 PM

zachary.leaf_arm.com added a parent revision: D39827: arm64 pmap: introduce PTE_TO_PHYS macro.Apr 26 2023, 12:25 PM

zachary.leaf_arm.com added reviewers: kib, markj.Apr 26 2023, 12:27 PM

zachary.leaf_arm.com added a reviewer: arm64.Apr 26 2023, 12:34 PM

I was initially confused by the macro name and no description. The purpose is to convert a physical address into the output address field of a PTE, not into PTE. At least a comment would be useful, if not a different name.

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Harbormaster completed remote builds in B51235: Diff 121130.Apr 27 2023, 12:18 PM

In D39828#906959, @kib wrote:

I was initially confused by the macro name and no description. The purpose is to convert a physical address into the output address field of a PTE, not into PTE. At least a comment would be useful, if not a different name.

Right. This is really only the first step in creating a PTE, we still need to set all the required attribute bits etc.

It's just about changing the representation back to the input address/pte format. e.g. for FEAT_LPA2, bits 51:50 of an OA are represented by bits 9:8 of the PTE so that will need switching around.

The only alternative I can think of is PA_TO_IA(...) but not sure that's any clearer and we lose the symmetry with PTE_TO_PA; have added a comment as suggested and updated commit message.

At least for now this step is mostly about documenting places where this change of representations will need to happen.

zachary.leaf_arm.com edited the summary of this revision. (Show Details)Apr 27 2023, 12:21 PM

In D39828#906959, @kib wrote:

I was initially confused by the macro name and no description. The purpose is to convert a physical address into the output address field of a PTE, not into PTE. At least a comment would be useful, if not a different name.

Would PA_TO_PTE_OE be better?

sys/arm64/arm64/pmap.c
2001

In D39828#907098, @andrew wrote:

In D39828#906959, @kib wrote:

I was initially confused by the macro name and no description. The purpose is to convert a physical address into the output address field of a PTE, not into PTE. At least a comment would be useful, if not a different name.

Would PA_TO_PTE_OE be better?

What does OE mean? O is perhaps output.

In D39828#907117, @kib wrote:

What does OE mean? O is perhaps output.

Should be OA for Output address, the field name in the documentation.

In D39828#907120, @andrew wrote:

In D39828#907117, @kib wrote:

What does OE mean? O is perhaps output.

Should be OA for Output address, the field name in the documentation.