linux-kernel - Re: [PATCHv2 02/13] kernel/cpu: Add support for declaring CPU offlining not supported

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Date:   Sat, 28 Oct 2023 16:07:21 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Huang, Kai" <kai.huang@...el.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>
Cc:     "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        "linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>,
        "ashish.kalra@....com" <ashish.kalra@....com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "thomas.lendacky@....com" <thomas.lendacky@....com>,
        "Hunter, Adrian" <adrian.hunter@...el.com>,
        "Reshetova, Elena" <elena.reshetova@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "bhe@...hat.com" <bhe@...hat.com>,
        "Nakajima, Jun" <jun.nakajima@...el.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "bp@...en8.de" <bp@...en8.de>,
        "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
        "rafael@...nel.org" <rafael@...nel.org>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCHv2 02/13] kernel/cpu: Add support for declaring CPU
 offlining not supported

On Mon, Oct 23 2023 at 22:07, Kai Huang wrote:
> On Mon, 2023-10-23 at 18:31 +0300, kirill.shutemov@...ux.intel.com wrote:
>> On Mon, Oct 23, 2023 at 09:30:59AM +0000, Huang, Kai wrote:
>> > IMHO it's a little bit odd to have two mechanisms in place, even in this middle
>> > state patch.  Is it better to completely replace CC_ATTR_HOTPLUG_DISABLED with
>> > the new cpu_hotplug_offline_disabled in this patch? You can explicitly call
>> > cpu_hotplug_disable_offlining() in tdx_early_init() so no functional change is
>> > done.
>> 
>> I can. But I don't see how it makes a difference.
>
> Personally I think this is better because it is odd to have two mechanisms in
> place even temporarily especially when we can avoid it.  But no hard opinion. 
> Up to you.

It's not at all better because having this clear split makes it simpler
to review and ponder the individual changes.

Thanks,

        tglx