linux-kernel - Re: [PATCHv2 19/29] x86/topology: Disable CPU online/offline control for TDX guests

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Date:   Thu, 03 Feb 2022 22:26:41 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Borislav Petkov <bp@...en8.de>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        mingo@...hat.com, dave.hansen@...el.com, luto@...nel.org,
        peterz@...radead.org, sathyanarayanan.kuppuswamy@...ux.intel.com,
        aarcange@...hat.com, ak@...ux.intel.com, dan.j.williams@...el.com,
        david@...hat.com, hpa@...or.com, jgross@...e.com,
        jmattson@...gle.com, joro@...tes.org, jpoimboe@...hat.com,
        knsathya@...nel.org, pbonzini@...hat.com, sdeep@...are.com,
        seanjc@...gle.com, tony.luck@...el.com, vkuznets@...hat.com,
        wanpengli@...cent.com, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 19/29] x86/topology: Disable CPU online/offline
 control for TDX guests

On Thu, Feb 03 2022 at 16:00, Borislav Petkov wrote:
> On Wed, Feb 02, 2022 at 01:11:56AM +0100, Thomas Gleixner wrote:
>> On Wed, Feb 02 2022 at 01:09, Thomas Gleixner wrote:
>> 
>> > On Mon, Jan 24 2022 at 18:02, Kirill A. Shutemov wrote:
>> >>  static bool intel_cc_platform_has(enum cc_attr attr)
>> >>  {
>> >> -	if (attr == CC_ATTR_GUEST_UNROLL_STRING_IO)
>> >> +	switch (attr) {
>> >> +	case CC_ATTR_GUEST_UNROLL_STRING_IO:
>> >> +	case CC_ATTR_HOTPLUG_DISABLED:
>> 
>> Not that I care much, but I faintly remember that I suggested that in
>> one of the gazillion of threads.
>
> Right, and yeah, adding a separate attribute is ok too but we already
> have a hotplug disable method. Why can't this call
>
> 	cpu_hotplug_disable()
>
> on the TDX init path somewhere and have this be even simpler?

That's daft. I rather have this explicit control which makes it obvious
what's going on.

Thanks,

        tglx