To shutdown the CPU, it is just the command "halt" in assembly, but to shutdown the system' powersupply, and all other component, nowdays it is hardwired to ACPI, eg:
So without ACPI, as mentioned in URL above, alternative is APM. Alternatively if u are talking about SMM/SMI, yes, sounds logical, as that is how system can shutdown itself after detecting overheating in motherboard (for example) - temperature monitoring is part of SMM mode. But I am not sure if u can trigger SMI that specifically shutdown system or not. (software trigger for SMI is possible ....port 0xb2)
Do aware that Intel VT (VMM) can intercept these SMI too:
On Wed, Jun 15, 2011 at 3:53 AM, limp <johnkyr83@xxxxxxxxxxx> wrote:
Hi all,
I am trying to figure out the procedure that Linux follows for shutting down
an x86 based system when ACPI is not used. From what I've found, when we try
to shutdown the system from user-space, _reboot() system call is called with
"LINUX_REBOOT_CMD_POWER_OFF" as argument. By tracking down the steps
performed in the kernel when the aforementioned system call is involved, I
ended up in kernel_power_off(), unlock_kernel(), and finaly do_exit()
functions.
The kernel_power_off() ultimately calls the native_machine_shutdown() form
which Linux disables LAPIC, I/O APIC, HPET, etc. Then, after calling the
unlock_kernel(), the do_exit() is called for ultimately shutting down the
system. In the end of this function, I can see that the processor enters an
infinite loop from which it repeatedly executes NOP instructions. That is
actually the behaviour that I experience when I am not using ACPI; the
system is not actually turning off but it goes into an idle state.
Is this how Linux should act when ACPI is not used? I would expect in this
case Linux to invoke an SMI so that the appropriate SMI function actually
shutdown the system but I can't see where (and if) that takes place.
Any help will be greatly appreciated.
John K.
_______________________________________________
Kernelnewbies mailing list
Kernelnewbies@xxxxxxxxxxxxxxxxx
http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
--
Regards,
Peter Teoh
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
