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Re: [Qemu-devel] target-i386: clear bsp bit when designating bsp
From: |
Andreas Färber |
Subject: |
Re: [Qemu-devel] target-i386: clear bsp bit when designating bsp |
Date: |
Tue, 07 Apr 2015 15:47:12 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 |
Am 07.04.2015 um 15:44 schrieb Denis V. Lunev:
> 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...
Yes, I intentionally left it out above as I don't think we need to trace
the local usage here. Worth mentioning in the commit message though.
Regards,
Andreas
--
SUSE Linux GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
GF: Felix Imendörffer, Jane Smithard, Jennifer Guild, Dilip Upmanyu,
Graham Norton; HRB 21284 (AG Nürnberg)
- Re: [Qemu-devel] target-i386: clear bsp bit when designating bsp, (continued)
- Re: [Qemu-devel] target-i386: clear bsp bit when designating bsp, Andreas Färber, 2015/04/07
- Re: [Qemu-devel] target-i386: clear bsp bit when designating bsp, Igor Mammedov, 2015/04/07
- Re: [Qemu-devel] target-i386: clear bsp bit when designating bsp, Andreas Färber, 2015/04/07
- Re: [Qemu-devel] target-i386: clear bsp bit when designating bsp, Paolo Bonzini, 2015/04/07
- Re: [Qemu-devel] target-i386: clear bsp bit when designating bsp, Andreas Färber, 2015/04/07
- Re: [Qemu-devel] target-i386: clear bsp bit when designating bsp, Paolo Bonzini, 2015/04/07
- Re: [Qemu-devel] target-i386: clear bsp bit when designating bsp, Paolo Bonzini, 2015/04/07
- Re: [Qemu-devel] target-i386: clear bsp bit when designating bsp, Denis V. Lunev, 2015/04/07
- Re: [Qemu-devel] target-i386: clear bsp bit when designating bsp, Paolo Bonzini, 2015/04/07
- Re: [Qemu-devel] target-i386: clear bsp bit when designating bsp, Denis V. Lunev, 2015/04/07
- Re: [Qemu-devel] target-i386: clear bsp bit when designating bsp,
Andreas Färber <=