linux-kernel - RE: [RFC PATCH v2 00/35] ACPI/arm64: add support for virtual cpuhotplug

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Message-ID: <622a39bda12a4b75a6da84f4566b4238@huawei.com>
Date:   Tue, 26 Sep 2023 13:16:41 +0000
From:   Salil Mehta <salil.mehta@...wei.com>
To:     James Morse <james.morse@....com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "loongarch@...ts.linux.dev" <loongarch@...ts.linux.dev>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        "kvmarm@...ts.linux.dev" <kvmarm@...ts.linux.dev>
CC:     "x86@...nel.org" <x86@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        "jianyong.wu@....com" <jianyong.wu@....com>,
        "justin.he@....com" <justin.he@....com>
Subject: RE: [RFC PATCH v2 00/35] ACPI/arm64: add support for virtual
 cpuhotplug

> From: James Morse <james.morse@....com>
> Sent: Wednesday, September 13, 2023 5:38 PM

[...]

> 
> Hello!
> 
> Changes since RFC-v1:
>  * riscv is new, ia64 is gone
>  * The KVM support is different, and upstream - no need to patch the host.
> 
> ---
> 
> This series adds what looks like cpuhotplug support to arm64 for use in
> virtual machines. It does this by moving the cpu_register() calls for
> architectures that support ACPI out of the arch code by using
> GENERIC_CPU_DEVICES, then into the ACPI processor driver.
> 
> The kubernetes folk really want to be able to add CPUs to an existing VM,
> in exactly the same way they do on x86. The use-case is pre-booting guests
> with one CPU, then adding the number that were actually needed when the
> workload is provisioned.
> 

[...]

> 
> I had a go at switching the remaining architectures over to
> GENERIC_CPU_DEVICES,
> so that the Kconfig symbol can be removed, but I got stuck with powerpc
> and s390.
> 
> I've only build tested Loongarch and riscv. I've removed the ia64 specific
> patches, but left the changes in other patches to make git-grep review of
> renames easier.
> 
> If folk want to play along at home, you'll need a copy of Qemu that
> supports this.
> https://github.com/salil-mehta/qemu.git salil/virt-cpuhp-armv8/rfc-v2-rc6


Please use the latest pushed RFC V2 instead:
https://lore.kernel.org/qemu-devel/20230926100436.28284-1-salil.mehta@huawei.com/T/#m523b37819c4811c7827333982004e07a1ef03879

Repository:
https://github.com/salil-mehta/qemu.git  virt-cpuhp-armv8/rfc-v2


Thanks
Salil.


[...]

> Why is this still an RFC? I'm still looking for confirmation from the
> kubernetes/kata folk that this works for them. Because of this I've culled
> the CC list...
> 
> 
> This series is based on v6.6-rc1, and can be retrieved from:
> https://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git/virtual_cpu_hotplug/rfc/v2