Messages in this thread | | | From | Linus Torvalds <> | Date | Wed, 17 Jan 2018 18:56:01 -0800 | Subject | Re: kexec reboot fails with extra wbinvd introduced for AME SME |
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On Wed, Jan 17, 2018 at 6:47 PM, Dave Young <dyoung@redhat.com> wrote: > Did several quick tests, probably need more tests, but till now the > results are: > > void stop_this_cpu(void *dummy) > { > =====> add wbinvd here: kexec works > local_irq_disable(); > =====> add wbinvd here: kexec works > /* > * Remove this CPU: > */ > set_cpu_online(smp_processor_id(), false); > =====> add wbinvd here: kexec does not work
Funky.
> So it seems that it will not work after cpu offined..
Well, that set_cpu_online() call really just clears a bit in our '__cpu_online_mask' CPU mask. It doesn't really do anything to the *hardware*.
But I do wonder if the wbinvd causes an SMI or something on your system. I _think_ wbinvd causes some external pin to be wiggled just to tell possible external cache hardware to flush too, and on a system level that could be tied to some random thing.
And then if we get an SMI/NMI when we've marked the system offline, maybe we do something odd.
Very odd. But maybe this makes somebody go "Duh, that's because of xyz.."
Linus
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