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SubjectRe: Why is double_fault serviced by a trap gate?
On Thu, 7 Dec 2000, Richard B. Johnson wrote:

> I am not denying the possibility of "warm-booting", i.e.,
> reloate some code to where there is a 1:1 physical to virtual
> translation, jump to the relocated code, disable paging, restart kernel
> code, and possibly examine what happened. You just have to get
> back to "flat-mode" with no paging to handle anything beyond a
> double fault. You are just not going to be able to restart
> from the stack-faulted code.

If you want to handle triple faults (well, there should be none of these
given a proper double fault handler) you may use the NMI as well. You are
guaranteed to receive a NMI after a while when the watchdog is active (it
is for SMP systems by default now and it will be for P6+ UP systems for
Linux 2.5 as well). At least current Intel chipsets do not assert RESET
to the CPU as a response to the shutdown special cycle in their default
configuration (we may even explicitly force that behaviour).

--
+ Maciej W. Rozycki, Technical University of Gdansk, Poland +
+--------------------------------------------------------------+
+ e-mail: macro@ds2.pg.gda.pl, PGP key available +

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