[coyotos-dev] SMP Patch 1

[Jeroen Visser]

On 10/24/07, Jonathan S. Shapiro <shap at eros-os.com> wrote:
> I have a nasty feeling that we just did a bunch of parallel effort
> again. The stuff I just committed is probably not right, and is
> certainly incomplete, but can you look it over?

It is fantastic. I learned a lot from your rewrite already. You commit
also shows proper names for variables and functions, as well as proper
layering (arch vs machine independent).

How about I get you the transmap patch against the latest repository?
After that I can integrate the good parts of my latest SMP work. Among
other things it addresses:

low map:

The AP bootstrap code page has been augmented with a boot map page (2
physical pages total for AP bootstrap). The boot map contains a copy
of the kernel map, but with a low alias. The kernel map never contains
a low mapping after arch_init.

on-demand AP boot pages:

The AP boot pages can be mapped and unmapped on demand. Combined with
the above we should be able to safely start APs (and perhaps reboot
them) while running. If that is not required we can use this code to
free up the AP bootstrap physical pages.

MY_CPU(booted) field:

Set to 1 when the apboot has been run and interrupts have been
enabled. The CPU is ready to dispatch its first process. In this mode
the CPU sits in a "hlt" loop until MY_CPU(active) becomes 1. To
actually start the CPU, set its active field to 1 and send it an IPI
to break out of the hlt loop. CPU 0 waits for this field to transition
from 0 -> 1 to detect AP spinup.

SMP command line options:

Options 'smp' and 'nosmp' controlling a variable named smp_enabled
which defaults to false for now.

AP bootstrap code cleanup:

Remove some unnecessary complexity. Use the new boot map page that was added.

-JCV