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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Borislav Petkov <bp@alien8.de>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        mingo@redhat.com, dave.hansen@intel.com, luto@kernel.org,
        peterz@infradead.org, sathyanarayanan.kuppuswamy@linux.intel.com,
        aarcange@redhat.com, ak@linux.intel.com, dan.j.williams@intel.com,
        david@redhat.com, hpa@zytor.com, jgross@suse.com,
        jmattson@google.com, joro@8bytes.org, jpoimboe@redhat.com,
        knsathya@kernel.org, pbonzini@redhat.com, sdeep@vmware.com,
        seanjc@google.com, tony.luck@intel.com, vkuznets@redhat.com,
        wanpengli@tencent.com, x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCHv2 19/29] x86/topology: Disable CPU online/offline
 control for TDX guests
In-Reply-To: <YfvuFADTO/f1UTG1@zn.tnic>
References: <20220124150215.36893-1-kirill.shutemov@linux.intel.com>
 <20220124150215.36893-20-kirill.shutemov@linux.intel.com>
 <87o83qw2m5.ffs@tglx> <87leyuw2ib.ffs@tglx> <YfvuFADTO/f1UTG1@zn.tnic>
Date:   Thu, 03 Feb 2022 22:26:41 +0100
Message-ID: <87wnibd4ku.ffs@tglx>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

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