linux-kernel - Re: [PATCH RFC 0/3] Support CPU hotplug for ARM64

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Message-ID: <135ee490-a5a6-46c9-208e-81849b20d6b6@huawei.com>
Date:   Thu, 4 Jul 2019 11:26:16 +0800
From:   Xiongfeng Wang <wangxiongfeng2@...wei.com>
To:     Jia He <hejianet@...il.com>, <rjw@...ysocki.net>,
        <catalin.marinas@....com>, <james.morse@....com>
CC:     <linux-acpi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <guohanjun@...wei.com>,
        <xiexiuqi@...wei.com>, <huawei.libin@...wei.com>,
        <john.garry@...wei.com>, <jonathan.cameron@...wei.com>
Subject: Re: [PATCH RFC 0/3] Support CPU hotplug for ARM64

Hi Justin,

On 2019/7/4 11:00, Jia He wrote:
> Hi Xiongfeng
> 
> It is a little bit awkful that I am also  investigating acpi based cpu hotplug issue silimar with
> 
> your idea. My question is your purpose to implement the vcpu hotplug in arm64 qemu?

Yes, my purpose is to implement the vcpu hotplug in arm64 qemu. So that I can add or remove vcpu
without shutting down the Guest OS.

Thanks,
Xiongfeng

> 
> Thanks for the ellaboration
> 
> ---
> Cheers,
> Justin (Jia He)
> 
> On 2019/6/28 19:13, Xiongfeng Wang wrote:
>> This patchset mark all the GICC node in MADT as possible CPUs even though it
>> is disabled. But only those enabled GICC node are marked as present CPUs.
>> So that kernel will initialize some CPU related data structure in advance before
>> the CPU is actually hot added into the system. This patchset also implement
>> 'acpi_(un)map_cpu()' and 'arch_(un)register_cpu()' for ARM64. These functions are
>> needed to enable CPU hotplug.
>>
>> To support CPU hotplug, we need to add all the possible GICC node in MADT
>> including those CPUs that are not present but may be hot added later. Those
>> CPUs are marked as disabled in GICC nodes.
>>
>> Xiongfeng Wang (3):
>>    ACPI / scan: evaluate _STA for processors declared via ASL Device
>>      statement
>>    arm64: mark all the GICC nodes in MADT as possible cpu
>>    arm64: Add CPU hotplug support
>>
>>   arch/arm64/kernel/acpi.c  | 22 ++++++++++++++++++++++
>>   arch/arm64/kernel/setup.c | 19 ++++++++++++++++++-
>>   arch/arm64/kernel/smp.c   | 11 +++++------
>>   drivers/acpi/scan.c       | 12 ++++++++++++
>>   4 files changed, 57 insertions(+), 7 deletions(-)
>>
> 
> .
>