Re: [Qemu-devel] Re: [RESENT][PATCH 2/2] x86: Issue reset on triple faults

[Jamie Lokier]

Jan Kiszka wrote:
> > It might be worth distinguishing between
> > triple-fault-used-by-guest-for-context-switch and triple faults which
> > trigger a normal reset, and log only the latter.  There's a
> > standardish way of distinguishing them, which the BIOS should check.
> 
> You refer to setting some return address at some magic BIOS location?

Probably; I forget the details.  There might be a CMOS byte, too.

> Isn't this something the BIOS should handle, not QEMU?

The BIOS should handle it, yes.  But since it is standard behaviour,
it might be useful for QEMU to decide whether to _log_ the event as a
system reset based on that state.

Same for keyboard controller induced reset - that's also used for
context switching, in the same way.  (Triple fault is only used
because it's faster.)

Same also for deciding whether -no-reboot should close down the QEMU
process.  Now I think about it, that is the best reason to distinguish
them!

> > When helper(SVM_EXIT_SHUTDOWN, 0) is called, should it still also call
> > qemu_system_reset_request()?
> 
> helper_vmexit() is not expected to return (cpu_loop_exit).

Ok.  It's not clear unless you know the code, which I don't.  Just
wanted to check :-)

-- Jamie