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

[Andreas Färber]

Am 07.04.2015 um 15:29 schrieb Paolo Bonzini:
> On 07/04/2015 15:24, Andreas Färber wrote:
>>>>     /* We hard-wire the BSP to the first CPU. */
>>>>     if (s->cpu_index == 0) {
>>>>         apic_designate_bsp(cpu->apic_state);
>>>>     }
>> I know, that's what this patch is changing, and I am saying that by the
>> same logic the CPU has no business fiddling with the APIC's apicbase
>> field when the APIC's reset is touching that very same field.
> 
> That's exactly what a real CPU does on power up or #RESET, though.

Does the APIC retain its BSP bit value on #RESET though? I doubt it.
It feels we're awkwardly working around qdev reset semantics here...

If you say the CPU must be in charge, then we should assure that the
APIC is reset before the CPU designates it and not have the APIC reset
callback retain such bits.

Admittedly, if this were for-2.3 (as which it is not marked) then this
patch may be the least intrusive. But it isn't and I've been preparing
to refactor the CPU-APIC relationship, so I really want to get it right
long-term.

Andreas

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