On Sat, Feb 18, 2012 at 12:49:16AM +0900, HATAYAMA Daisuke wrote: > A few days ago I investigted the case where system is reseted due to > triple fault caused by the NMI after idt is disabled in > machine_kexec. I didn't see the reset when trigering the kdump with > NMI since the NMI is masked until next iret instruction executed as > described in 6.7.2. Handling Multiple NMIs of Intel Manual Vol.3A. > The NMI mask remains untill the first iret execution on the 2nd > kernel: just the return path of the first kernel_thread invocation for > init process. The exact path is: hmm. So even though the local apic was disabled you still got an NMI? That could have been from an external NMI. I forget how that is wired up, if it goes through the IOAPIC to the Local APIC or directly to the NMI pin on the cpu. > > switch_to > -> ret_from_fork > -> int_ret_from_sys_call > -> retint_restore_args > -> irq_return > > At that phase idt is already set up and kdump works. > > From the discussion I interpret kdump doesn't assume this behaviour, > right? probably not. > > BTW, does anyone know the detail of the NMI mask? I couldn't figure > out about it from the Intel spec more than ``certain hardware > conditions''... I expect those who look at here are x86 NMI experts. I don't understand the question. Cheers, Don
