RE: [PATCH RFC V5 00/30] Support of Virtual CPU Hotplug for ARMv8 Arch

[Salil Mehta via <qemu-devel@nongnu.org>]

HI Gavin,

> -----Original Message-----
> From: Gavin Shan <gshan@redhat.com>
> Sent: Thursday, May 22, 2025 12:54 AM
> To: Gustavo Romero <gustavo.romero@linaro.org>; Salil Mehta
> <salil.mehta@huawei.com>; qemu-devel@nongnu.org; qemu-
> arm@nongnu.org; mst@redhat.com; Jonathan Cameron
> <jonathan.cameron@huawei.com>; Igor Mammedov
> <imammedo@redhat.com>; Eric Auger <eauger@redhat.com>

[..]

> 
> Hi Gustavo and Salil,
> 
> On 5/22/25 1:06 AM, Gustavo Romero wrote:
> > Hi Salil, Gavin, and folks,
> >
> > On 5/20/25 21:22, Gavin Shan wrote:
> >> Hi Salil,
> >>
> >> A kindly ping. vCPU hotplug is an important feature and You has put
> >> so much energies and amazing efforts to enable the feature from QEMU
> >> side, but it seems it has been stuck recently. I received many
> >> messages from Redhat internal and external to ask if vCPU hotplug has
> >> been supported on aarch64 in the past. So I'm heading up to check if
> >> you have bandwidth to continue the effort, any kinds of helps are
> needed, especially from me.
> >
> > You can count on me as well, Salil. I'm definitely in a better
> > position now to help you with the technical review of the series, and
> > I can also weigh in to help resolve any remaining issues so we can
> > finally get it merged. Don't give up! :)
> >
> > My suggestion: go ahead and post what you have now. Just highlight the
> > main points of objection raised in the last review that still need to be
> addressed.
> >
> 
> Thanks for your response and to offer helps. Another suggestion I have in
> mind:
> if there is uncertainty regarding the design, it would be nice to post a specific
> thread for discussion until it's cleared prior to diving into code. After the
> design is acknowledged by maintainers, our life will be much easier. The
> point is to get enough attentions and feedbacks from the maintainers until
> it's acknowledged.


The changes were mainly to address Igor's concern which have to be respected
as he is a maintainer of vCPU hotplug on x86. And to ensure that his time is
utilized best as he is understandably a busy person, we all thought to share the
updated code to him.

There are design changes but these are not which makes the design completely
different as we have to respect the interfaces which have been frozen with the
kernel and hence the handshakes ideally should remain same. Also, as part of
the review, I've had some internal discussions related to these changes in Huawei
with Jonathan and he was in agreement with the approach. But of course, end
acknowledgement has to come from Igor. 😊

 
> >> Besides, I'm reluctantly to ask if you're fine for some body else to
> >> pick this up and continue the effort. The credits for all the
> >> contributors (Keqian Zhu, Jean Philippe, Miguel Luis and you) will be kept.
> >
> > I don’t want to speak for others, but in my view, Salil should ideally
> > be the one to complete this work — as you said, he’s already invested
> > a great deal of time and energy into it.
> >
> > It would be tremendously helpful if maintainers could support Salil in
> > bringing this to completion, kindly guiding him toward the path to get it
> finalized.
> >
> 
> Absolutely, Salil knows all the details, especially the historic steps how vCPU
> hotplug has been evolving. I truly hope Salil is able to continue the efforts
> until the feature lands upstream!


Sorry, for any hassle caused due to my absences. Yes, I'm back to work and will
try to expedite the changes and ping you soon for your help.

Thanks for understanding.

Best regards
Salil.


> 
> Thanks,
> Gavin
>