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SubjectRe: [PATCH v6 04/12] x86/smpboot.c: Don't offline CPU0 if any irq can not be migrated out of it and remove CPU0 check in smp_callin()

* H. Peter Anvin <hpa@zytor.com> wrote:

> On 05/14/2012 05:17 AM, Ingo Molnar wrote:
> >
> > * Tony Luck <tony.luck@intel.com> wrote:
> >
> >> Biggest code impact of that is the extra code to bring cpu0
> >> back online using NMI instead of INIT. We can't use INIT
> >> because if cpu0 gets one, it just resets the whole machine :-(
> >> But obviously we'd like to avoid special cases where there is
> >> a sane way to do so.
> >
> > Could we just standardize on NMI bringup during regular bootup?
> >
>
> The first instance has to be SIPI because you can't give the
> CPU an NMI without the IDT being setup. We *could* assume
> that the processor is parked in real mode with the valid
> real-mode IDT set up (in which case the vector at physical
> address 8 applies) but that seems to assume a lot from the
> BIOS for little gain. In particular I suspect that UEFI-based
> BIOSes may very well park the CPU in protected or long mode.

Ok, fair enough.

Thanks,

Ingo


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