Re: [Qemu-devel] [PATCH qemu-kvm] Fix: SCI isn't sent on cpu hotplug

[Jan Kiszka]

On 2012-01-09 12:07, Igor Mammedov wrote:
> On 01/09/2012 11:19 AM, Jan Kiszka wrote:
>> On 2012-01-09 11:07, Gleb Natapov wrote:
>>> On Mon, Jan 09, 2012 at 11:03:10AM +0100, Jan Kiszka wrote:
>>>> On 2012-01-09 09:47, Gleb Natapov wrote:
>>>>> On Sun, Jan 08, 2012 at 10:40:04PM +0100, Igor Mammedov wrote:
>>>>>>   Change introduced by e71f08bb4a
>>>>>>      "Fix cpu/pci hotplug to generate level triggered interrupt."
>>>>>>   was lost somewhre along the way. And as result SCI is not sent in
>>>>>>   case of cpu hotplug event.
>>>>>>   Restoring hunk 1 of e71f08bb4a fixes issue.
>>>>>>
>>>>> Hmm, I sent similar patch [1] last time someone complained about cpu 
>>>>> hotplug
>>>>> here. Which remind me that in that thread more problem were found in cpu
>>>>> hotplug. IIRC Jan collected all the patches. Jan, what happened to
>>>>> them?
>>>>
>>>> My patches should have been superseded by the work of Ping Fan on the
>>>> ICC bus.
>>>>
>>> Didn't they fix some problems with bringing new cpu online, not just
>>> making cpu hotplugable in qdev? May be I misremember.
>>
>> Let me check... Hmm, yes, there were also some bits required to bring up
>> the new VCPU thread properly and sync its initial state to the kernel.
> 
> CPU bring-up seems to be broken now, guest sees a new cpu but I can't
> online it inside guest with error: "CPUx: Not responding". But it
> works with old qemu-kvm [3925c857a574].
> Jan could you point me to this patches?

See
http://git.kiszka.org/?p=qemu-kvm.git;a=commitdiff;h=be8f21c6b54eac82f7add7ee9d4ecf9cb8ebb320

Its dependencies have been merged by now. The key is that you need to
synchronize VCPU initialization with the other QEMU threads (so that no
semi-initialized VCPU is visible at any time) and that you perform a
cpu_synchronize_post_init on that VCPU. The hotplug hack is replaced by
the ICC approach.

> 
>> That was not part of Ping Fan's ICC patches, also not of the VCPU life
>> cycle patches.
> 
> I'm trying to re-base cpu-hotplug to qemu.git, and with ICC patches it's
> working like the current qemu-kvm head. But without above mentioned fixes
> it seams to be useless.

Make sure to work against qemu first. Getting things rolling with
qemu-kvm is usually trivial. Working the other way around may create new
forks again.

Jan

-- 
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux