linux-kernel - Re: [RFC PATCH 00/32] ACPI/arm64: add support for virtual cpuhotplug

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Message-ID: <1ca1fb8f-1dec-74a3-ee44-94609f6aba2c@arm.com>
Date:   Tue, 12 Sep 2023 18:01:28 +0100
From:   James Morse <james.morse@....com>
To:     Gavin Shan <gshan@...hat.com>, linux-pm@...r.kernel.org,
        loongarch@...ts.linux.dev, kvmarm@...ts.linux.dev,
        kvm@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-ia64@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        x86@...nel.org
Cc:     Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Borislav Petkov <bp@...en8.de>, H Peter Anvin <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Huacai Chen <chenhuacai@...nel.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Len Brown <lenb@...nel.org>,
        Rafael Wysocki <rafael@...nel.org>,
        WANG Xuerui <kernel@...0n.name>,
        Salil Mehta <salil.mehta@...wei.com>,
        Russell King <linux@...linux.org.uk>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>
Subject: Re: [RFC PATCH 00/32] ACPI/arm64: add support for virtual cpuhotplug

Hi Gavin,

On 29/03/2023 03:35, Gavin Shan wrote:
> On 2/3/23 9:50 PM, James Morse wrote:

>> 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-v1-port29092022.psci.present
>>
>> You'll need to fix the numbers of KVM_CAP_ARM_HVC_TO_USER and KVM_CAP_ARM_PSCI_TO_USER
>> to match your host kernel. Replace your '-smp' argument with something like:
>> | -smp cpus=1,maxcpus=3,cores=3,threads=1,sockets=1
>>
>> then feed the following to the Qemu montior;
>> | (qemu) device_add driver=host-arm-cpu,core-id=1,id=cpu1
>> | (qemu) device_del cpu1
>>
>>
>> This series is based on v6.2-rc3, and can be retrieved from:
>> https://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git/ virtual_cpu_hotplug/rfc/v1

> I give it a try, but the hot-added CPU needs to be put into online
> state manually. I'm not sure if it's expected or not.

This is expected. If you want the CPUs to be brought online automatically, you can add
udev rules to do that.


Thanks,

James