Re: [PATCH] Use BIOS reboot on Toshiba Portege 4000

On Tue, Nov 04, 2008 at 03:22:30AM -0800, Eric W. Biederman wrote:
Avi Kivity <avi@xxxxxxxxxx> writes:

Eric W. Biederman wrote:
I think we are confusing two issues here.

- Ordinary machine_restart which happens to call emergency_restart.
And is proceeded by machine_shutdown.

- And emergency_restart itself.

To some extent I would be a lot happier if Alt-sysrq-r did what
was necessary to get into a context where it can call machine_restart
or even better kernel_restart().
emergency_restart() is a nice idea but is broken by design.



Isn't emergency_restart() equivalent to kexec()? Both start from indeterminite
conditions.

Good point. That is a reasonable direction to evolve it on x86.
Similar to and sharing some of the same code as the kexec on panic path.

We may need to separate out emergency_restart from the normal clean
restart to make that happen. It would be pointless and silly to be
sending NMI at other cpus for example if we have cleanly shut them
down already.

When pulling the NMI stuff to the reboot code, I've just hit this issue:
currently, machine_ops.emergency_restart has two possible semantics:

- The function that should be called to immediately reboot the machine,
after the cleanup done by machine_restart()
- The function that should be called to reboot the machine when we are
on a possibly inconsistent state (and will do the vmx-disabling
stuff)

Currently we don't do anything special on emergency_restart() case,
so both cases are equivalent. But now we will need to differentiate
both cases.


...all this work because VMX breaks the good old reset lines. :\

--
Eduardo
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