CVS commit: src/sys/arch/amd64

["Maxime Villard" <maxv%netbsd.org@localhost>]

Module Name:    src
Committed By:   maxv
Date:           Thu Oct 19 18:36:31 UTC 2017

Modified Files:
        src/sys/arch/amd64/acpi: acpi_wakeup_low.S
        src/sys/arch/amd64/amd64: locore.S machdep.c

Log Message:
Improve our segregs model. Pass 1/3.

Right now, we are saving and restoring %ds/%es each time we enter/leave the
kernel. However, we let %fs/%gs live in the kernel space, and we rely on
the fact that when switching to an LWP, %fs/%gs are set right away (via
cpu_switchto or setregs).

It has two drawbacks: we are taking care of %ds/%es while they are
deprecated (useless) on 64bit LWPs, and we are restricting %fs/%gs while
they still have a meaning on 32bit LWPs.

Therefore, handle 32bit and 64bit LWPs differently:
 * 64bit LWPs use fixed segregs, which are not taken care of.
 * 32bit LWPs have dynamic segregs, always saved/restored.

For now, only %ds and %es are changed; %fs and %gs will be in the next
passes.

The trapframe is constructed as usual. In INTRFASTEXIT, we restore %ds/%es
depending on the %cs value. If %cs contains one of the two standard 64bit
selectors, don't do anything. Otherwise, restore everything.

When doing a context switch, just restore %ds/%es to their default values.
On a 32bit LWP they will be overwritten by INTRFASTEXIT; on a 64bit LWP
they won't be updated.

In the ACPI wakeup code, restore %ds/%es to the default 64bit user value.


To generate a diff of this commit:
cvs rdiff -u -r1.6 -r1.7 src/sys/arch/amd64/acpi/acpi_wakeup_low.S
cvs rdiff -u -r1.133 -r1.134 src/sys/arch/amd64/amd64/locore.S
cvs rdiff -u -r1.269 -r1.270 src/sys/arch/amd64/amd64/machdep.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.