amd64 acpi_wakeup: map 1:1 whole low 4G for initial page table
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Authored by kib on Sep 11 2021, 6:42 PM.

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This is required since kernel text might be physically located anywhere below 4G.

Also avoid touching unowned low memory when booted from UEFI.

PR: 258432

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rG FreeBSD src repository

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kib requested review of this revision.Sep 11 2021, 6:42 PM

kib created this revision.

Do not forget to install KVA mappings into the trampoline page table.

kib edited the summary of this revision. (Show Details)Sep 12 2021, 5:53 PM

kib added a reviewer: markj.

markj added inline comments.

sys/x86/acpica/acpi_wakeup.c
517	Why do we set PG_U here?

This revision is now accepted and ready to land.Sep 13 2021, 12:41 PM

sys/x86/acpica/acpi_wakeup.c
517	I do not think there is a reason now. It might be there was some reason before, if e.g. vm86 mode was used on the wakeup path [Or any other trampoline from real mode to final protection mode, we are consistent to set PG_U on all trampoline ptes, I believe] So it probably was moved from i386 to amd64 and live there since. I have another change to the acpi_wakeup.c in pipe, after that I might look into coalescing code that creates page table for low 4G 1:1.