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Re: [Qemu-ppc] [PATCH] spapr: support CPU hotplug
From: |
Alexander Graf |
Subject: |
Re: [Qemu-ppc] [PATCH] spapr: support CPU hotplug |
Date: |
Tue, 27 Aug 2013 10:54:22 +0200 |
On 27.08.2013, at 09:41, Alexey Kardashevskiy wrote:
> On 08/27/2013 05:02 PM, Paolo Bonzini wrote:
>> Il 27/08/2013 08:37, Alexey Kardashevskiy ha scritto:
>>>>> So this is here to make sure we don't accidentally get out of halted
>>>>> state by an interrupt on that vcpu. Could you please somehow make that
>>>>> part obvious? Either by adding a comment or by only explicitly masking
>>>>> DEC and EE and a comment :).
>>>>>
>>>>>> + cs->exit_request = 1;
>>>>>
>>>>> This should probably be qemu_cpu_kick_self().
>>>>
>>>> Uh, no, I don't think so. This is there purely to make sure we exit
>>>> the inner loop, and actually test cpu_can_run() which will test
>>>> halted. AFAICT qemu_cpu_kick_self() won't do anything similar.
>>>
>>> rtas_stop_self() eventually returns to kvm_cpu_exec() which calls
>>> qemu_cpu_kick_self() and resets cs->exit_request before return so I do not
>>> really see the difference in behaviour. And actually both ways CPU stops in
>>> exactly the same way. What do I miss?
>>
>> What about TCG?
>
> Oh. Right. TCG :(
>
> qemu_cpu_kick_self() crashes the guest and cs->exit_request works fine.
>
> Why? Both should work? What is the expected behavior here? Thanks.
Hrm. To me exit_request always was an internal piece of state that the inner
loop uses to find out whether to exit, but not something we should randomly set
from a device (and hypercalls / rtas calls are very similar to devices). So I
would like to not have any code in hw/ that modifies it.
However, we need the functionality of breaking out of the main loop, I agree.
Maybe what you are really looking for is cpu_interrupt(CPU_INTERRUPT_HALT).
That sets halted = 1 and exits the main loop, because it's an interrupt.
Alex
- [Qemu-ppc] [PATCH] spapr: support CPU hotplug, Alexey Kardashevskiy, 2013/08/23
- Re: [Qemu-ppc] [PATCH] spapr: support CPU hotplug, Alexander Graf, 2013/08/26
- Re: [Qemu-ppc] [PATCH] spapr: support CPU hotplug, David Gibson, 2013/08/26
- Re: [Qemu-ppc] [PATCH] spapr: support CPU hotplug, Alexey Kardashevskiy, 2013/08/27
- Re: [Qemu-ppc] [PATCH] spapr: support CPU hotplug, Paolo Bonzini, 2013/08/27
- Re: [Qemu-ppc] [PATCH] spapr: support CPU hotplug, Alexey Kardashevskiy, 2013/08/27
- Re: [Qemu-ppc] [PATCH] spapr: support CPU hotplug,
Alexander Graf <=
- Re: [Qemu-ppc] [PATCH] spapr: support CPU hotplug, Alexey Kardashevskiy, 2013/08/27
- Re: [Qemu-ppc] [PATCH] spapr: support CPU hotplug, Alexander Graf, 2013/08/27