Re: [Qemu-devel] target-i386: clear bsp bit when designating bsp

[Andreas Färber]

Am 07.04.2015 um 12:54 schrieb Paolo Bonzini:
> On 07/04/2015 12:44, Andreas Färber wrote:
>>>> It can change at runtime, though, if you're using the KVM in-kernel LAPIC.
>> Got a pointer? A quick git-grep doesn't show anything in hw/ or
>> kvm-all.c or target-i386/ assigning cpu_index, so it'll always have the
>> initial value.
> 
> Not cpu_index, s->apicbase's MSR_IA32_APICBASE_BSP bit can change with
> KVM in-kernel LAPIC.  It cannot change with QEMU's userspace LAPIC.
> 
> Because it can change, you have to call apic_designate_bsp for all CPUs
> and not only on CPU 0.

Now I'm even more confused. Surely CPUState is initially
zero-initialized. Then we designate one as BSP on reset. That should be
the same result as designating all non-BSP CPUs, no? The only way that
would change is then cpu_index == 0 goes away (hot-unplug, not
implemented yet), and in that case it would be about designating a
different CPU, not about un-designating one.

If this is some issue with sync'ing state back and forth before QEMU and
KVM then the real issue has not been explained.

Andreas

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