Re: CVS commit: src/sys/arch

[Maxime Villard <max%m00nbsd.net@localhost>]

Le 04/08/2016 à 21:09, Joerg Sonnenberger a écrit :
> On Sun, Jul 24, 2016 at 02:09:22PM +0000, Maxime Villard wrote:
> > Fix this by properly saving and restoring the EFER MSR. It's a little
> > tricky since the wakeup code uses %edx, but rdmsr overwrites it. We just
> > save it in %esi.
>
> Use push/pop around it, please?

Around what, where?

If you're talking about the calling convention, as far as I can tell, it is
respected here. In acpi_md_sleep_exit the CPU just woke up, so there is no need
to push anything.

If you're talking about why %edx is saved in %esi instead of being pushed on
the stack, it's because the stack pointer points to page 1 (in pa), but in the
i386 machdep code this area is referred to as BIOS callback. It didn't seem to
make much sense to me, so, not to add more confusion, I preferred to do the data
transfers between registers instead of touching the stack.

If you're talking about the msr stuff, as far as I can tell, the registers are
properly saved before being overwritten.

Unless I missed something.

Note: if you are talking about 2), I don't think pushing the register on the
stack would work, since paging is enabled and page 1 is not present in the
temporary page tree.