linux-kernel - Re: [PATCH v8 02/11] x86/tdx: Introduce INTEL_TDX

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Date:   Tue, 5 Oct 2021 19:29:12 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     Sathyanarayanan Kuppuswamy Natarajan 
        <sathyanarayanan.nkuppuswamy@...il.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Juergen Gross <jgross@...e.com>, Deep Shah <sdeep@...are.com>,
        VMware Inc <pv-drivers@...are.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, Peter H Anvin <hpa@...or.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8 02/11] x86/tdx: Introduce INTEL_TDX_GUEST config option

On Tue, Oct 05, 2021 at 07:48:25AM -0700, Kuppuswamy, Sathyanarayanan wrote:
> Since x2APIC will always exist in TDX guest case, we have used select to
> enable the support. But since we have dependency on it, I  think "depends"
> might be a better choice.

Right, and while we're on the subject, this looks silly to me too:

+       depends on SECURITY
...
+       select SECURITY_LOCKDOWN_LSM

because

Symbol: SECURITY_LOCKDOWN_LSM [=n]
  │ Type  : bool
  │ Defined at security/lockdown/Kconfig:1
  │   Prompt: Basic module for enforcing kernel lockdown
  │   Depends on: SECURITY [=n]
		  ^^^^^^^^^

so that symbol already depends on SECURITY.

And I have SECURITY=n in my config so I still have to go select SECURITY
by hand so that CONFIG_INTEL_TDX_GUEST becomes visible. And when I
select it, SECURITY_LOCKDOWN_LSM gets enabled too.

But since I have to go select SECURITY, I can just as well enable
SECURITY_LOCKDOWN_LSM in order to have TDX guest support.

IOW, I don't see the point for the evil "select"s - just make everything
depends on and be done with it.

Unless there's an aspect I'm missing...

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette