amd64: stop doing special allocation for the AP startup trampoline
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Authored by kib on Jul 29 2021, 12:27 AM.

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markj
alc

Commits

rG2572376f7f64: amd64: do not touch low memory in AP startup unless we used legacy boot
rGb27fe1c3ba2a: amd64: stop doing special allocation for the AP startup trampoline

Summary

There is no reason now why do we need to allocate trampoline page very early in the boot process. The only requirement for the page is that it is below 1M to be usable by the real mode during init. This can be handled by vm_alloc_contig() when we do the startup.

Also assert that startup trampoline fits into single page. In principle we can do multi-page allocation if needed, but it is not.

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rG FreeBSD src repository

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Event Timeline

kib requested review of this revision.Jul 29 2021, 12:27 AM

kib created this revision.

The only requirement for the page is that it is below 1G to be usable by the real mode during init.

Should be 1M.

x86_smp.h still declares alloc_ap_trampoline() on amd64. Perhaps just wrap the declaration with an ifdef i386?

sys/amd64/amd64/mp_machdep.c
342	I think `boot_address` can become a local variable which gets passed to `start_ap()`.

Make boot_address local for amd64/mp_machdep.c.
Brace i386 specific definitions in x86/include
Fix typo in summary
Fix several more cases where lower memory touched by EFI booted kernel (will be a separate commit)

markj accepted this revision.Jul 29 2021, 1:27 PM

This revision is now accepted and ready to land.Jul 29 2021, 1:27 PM

Closed by commit rGb27fe1c3ba2a: amd64: stop doing special allocation for the AP startup trampoline (authored by kib). · Explain WhyJul 29 2021, 10:21 PM

This revision was automatically updated to reflect the committed changes.

kib added a commit: rGb27fe1c3ba2a: amd64: stop doing special allocation for the AP startup trampoline.

kib added a commit: rG2572376f7f64: amd64: do not touch low memory in AP startup unless we used legacy boot.