[edk2-devel] [RFC PATCH 0/5] support CPU hot-unplug

[Laszlo Ersek]

On 12/21/20 15:44, Laszlo Ersek wrote:
> Hi Ankur,
> 
> On 12/08/20 06:34, Ankur Arora wrote:
>> [ Resending to the correct edk2 alias this time. ]
>>
>> Hi,
>>
>> This series adds support for CPU hot-unplug with OVMF.
>>
>> Please see this in conjunction with the QEMU v2 series posted here: 
>>   https://lore.kernel.org/qemu-devel/20201207140739.3829993-1-imammedo@redhat.com/
>>
>> In particular, would be glad for comments on Patch 4, specifically
>> where we should be ejecting the CPU. 
>>
>> Right now the ejection happens in UnplugCpus() (called from
>> CpuHotplugMmi()):
>>   +    QemuCpuhpWriteCpuSelector (mMmCpuIo, RemoveApicId);
>>   +    QemuCpuhpWriteCpuStatus (mMmCpuIo, QEMU_CPUHP_STAT_EJECTED);
>>
>> That is way too early -- given that the actual unplug will happen
>> in SmmCpuUpdate() and given that the BSPHandler() would have waited
>> for the APs multiple times before then.
>>
>> Another possibility is that the actual ejection be deferred to the
>> _EJ0 method after the return from the SMI. But, that seems like a
>> hack. Additionally, Igor points out here that this approach has problems:
>>   https://lore.kernel.org/qemu-devel/20201204170939.1815522-1-imammedo@redhat.com/
> 
> I've filed:
> 
>   https://bugzilla.tianocore.org/show_bug.cgi?id=3132
> 
> Can you please register an account in the TianoCore Bugzilla at
> <https://bugzilla.tianocore.org/>, and assign the above ticket to yourself?
> 
> And then, the URL of the new BZ ticket should be included in every
> commit message, like this:
> 
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3132
> 
> just above your S-o-b.
> 
> No need to repost just because of this; I'll review the RFC series later.

I've also listed <https://bugzilla.tianocore.org/show_bug.cgi?id=3132>
under
<https://github.com/tianocore/tianocore.github.io/wiki/EDK-II-Release-Planning#edk2-stable202102-tag-planning>.

Thanks
Laszlo



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