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Re: [Qemu-devel] [PATCH 0/4] s390: Allow hotplug of s390 CPUs
From: |
Matthew Rosato |
Subject: |
Re: [Qemu-devel] [PATCH 0/4] s390: Allow hotplug of s390 CPUs |
Date: |
Mon, 9 Nov 2015 11:07:03 -0500 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 |
On 11/09/2015 10:55 AM, Christian Borntraeger wrote:
> Am 09.11.2015 um 16:37 schrieb Christian Borntraeger:
>> Am 09.11.2015 um 16:35 schrieb Christian Borntraeger:
>>> Am 09.11.2015 um 16:28 schrieb Andreas Färber:
>>>> Hi,
>>>>
>>>> Am 09.11.2015 um 16:17 schrieb Matthew Rosato:
>>>>> To subsequently hotplug a CPU:
>>>>>
>>>>> Issue 'cpu-add <id>' from qemu monitor, or use virsh setvcpus --count <n>
>>>>> <domain>, where <n> is the total number of desired guest CPUs.
>>>>
>>>> What exactly is still missing for you to use the standard device_add?
>>>>
>>>> Last time I checked (a while ago...) some patches were stuck on the x86
>>>> side, and I don't recall hearing any feedback from the s390x side in my
>>>> KVM Forum CPU hotplug session.
>>>
>>> libvirt uses "cpu-add" unconditionally for hotplugging, so we certainly
>>> want to support that.
>>
>> Sorry, hit send too early. I assume you want us to support device_add of
>> a CPU in addition to that. Correct?
>
> I just did a quick test with Matts patch.
>
> after applying
>
> diff --git a/qom/cpu.c b/qom/cpu.c
> index fb80d13..8152744 100644
> --- a/qom/cpu.c
> +++ b/qom/cpu.c
> @@ -360,7 +360,7 @@ static void cpu_class_init(ObjectClass *klass, void *data)
> * Reason: CPUs still need special care by board code: wiring up
> * IRQs, adding reset handlers, halting non-first CPUs, ...
> */
> - dc->cannot_instantiate_with_device_add_yet = true;
> +// dc->cannot_instantiate_with_device_add_yet = true;
> }
>
> static const TypeInfo cpu_type_info = {
>
> I was able to use
>
> device_add s390-cpu
>
> but no comprehensive testing was done.
> I was even able to add more cpus than maxcpus, but the guest could not
> make use of it. Fix is probably easy. But in general it looks like
> that we _could_ enable device_add for CPUs as soon as others are ready
> as well.
> Matt, do you agree?
>
Yes, I'm seeing the same behavior. We're just not checking max_cpus in
device init, but the "extra" CPUs cannot be brought online.
Matt
- [Qemu-devel] [PATCH 0/4] s390: Allow hotplug of s390 CPUs, Matthew Rosato, 2015/11/09
- [Qemu-devel] [PATCH 1/4] s390x/cpu: Cleanup init in preparation for hotplug, Matthew Rosato, 2015/11/09
- [Qemu-devel] [PATCH 2/4] s390x/cpu: Set initial CPU state in common routine, Matthew Rosato, 2015/11/09
- [Qemu-devel] [PATCH 3/4] s390x/cpu: Add function to set CPU state, Matthew Rosato, 2015/11/09
- [Qemu-devel] [PATCH 4/4] s390x/cpu: Allow hotplug of CPUs, Matthew Rosato, 2015/11/09
- Re: [Qemu-devel] [PATCH 0/4] s390: Allow hotplug of s390 CPUs, Andreas Färber, 2015/11/09