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Date: Tue, 7 Apr 2015 16:44:42 +0300
From: "Denis V. Lunev" <den@openvz.org>
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Subject: Re: [Qemu-devel] target-i386: clear bsp bit when designating bsp
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To: Paolo Bonzini <pbonzini@redhat.com>, "Denis V. Lunev" <den@openvz.org>, =?windows-1252?Q?Andreas_F=E4rber?= <afaerber@suse.de>, qemu-devel@nongnu.org
Cc: Eduardo Habkost <ehabkost@redhat.com>, Nadav Amit <namit@cs.technion.ac.il>, mst@redhat.com, Igor Mammedov <imammedo@redhat.com>, nadav.amit@gmail.com, rth@twiddle.net

On 07/04/15 16:29, Paolo Bonzini wrote:
>
>
> On 07/04/2015 15:26, Denis V. Lunev wrote:
>> On 07/04/15 16:18, Paolo Bonzini wrote:
>>>
>>>
>>> On 07/04/2015 13:57, Andreas Färber wrote:
>>>>>> If this is some issue with sync'ing state back and forth before
>>>>>> QEMU and
>>>>>> KVM then the real issue has not been explained.
>>>> Hm, hw/intc/apic_common.c:apic_reset_common() has:
>>>>
>>>>       bsp = cpu_is_bsp(s->cpu);
>>>>       s->apicbase = APIC_DEFAULT_ADDRESS |
>>>>           (bsp ? MSR_IA32_APICBASE_BSP : 0) | MSR_IA32_APICBASE_ENABLE;
>>>>
>>>> What this is doing is really:
>>>>
>>>>       bsp = cpu_get_apic_base(s->cpu->apic_state) &
>>>> MSR_IA32_APICBASE_BSP;
>>>>       s->apicbase = APIC_DEFAULT_ADDRESS |
>>>>           (bsp ? MSR_IA32_APICBASE_BSP : 0) | MSR_IA32_APICBASE_ENABLE;
>>>>
>>>> Unless I'm missing something, since we are in the APIC device's reset
>>>> function, this is effectively a twisted way of writing:
>>>>
>>>>       bsp = s->apicbase & MSR_IA32_APICBASE_BSP;
>>>>       s->apicbase = APIC_DEFAULT_ADDRESS |
>>>>           (bsp ? MSR_IA32_APICBASE_BSP : 0) | MSR_IA32_APICBASE_ENABLE;
>>>
>>> Yes, this is more readable.
>>
>> just $0.02 :)
>>
>> why don't
>>          bsp = s->apicbase & MSR_IA32_APICBASE_BSP;
>>          s->apicbase =
>>          APIC_DEFAULT_ADDRESS | bsp | MSR_IA32_APICBASE_ENABLE;
>> in this case. This looks the same from the textual point of view.
>
> Yes.  Would you like to send a patch?
>
> Paolo
>

no prob, just give me 2 minutes. Side note, bsp will become uint32_t
and we will loose tracepoint inside cpu_get_apic_base() on this
path...

Den