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

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Summary

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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R10 FreeBSD src repository
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Event Timeline

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

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

kib added a reviewer: markj.
markj added inline comments.
sys/x86/acpica/acpi_wakeup.c
506

Why do we set PG_U here?

This revision is now accepted and ready to land.Mon, Sep 13, 12:41 PM
sys/x86/acpica/acpi_wakeup.c
506

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.