linux-kernel - Re: [PATCH 02/26] x86/tdx: Extend the cc_platform

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Date:   Thu, 16 Dec 2021 19:33:50 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     tglx@...utronix.de, 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: [PATCH 02/26] x86/tdx: Extend the cc_platform_has() API to
 support TDX guests

On Tue, Dec 14, 2021 at 06:02:40PM +0300, Kirill A. Shutemov wrote:
> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> 
> Confidential Computing (CC) features (like string I/O unroll support,
> memory encryption/decryption support, etc) are conditionally enabled
> in the kernel using cc_platform_has() API. Since TDX guests also need
> to use these CC features, extend cc_platform_has() API and add TDX
> guest-specific CC attributes support.
> 
> Use is_tdx_guest() API to detect for the TDX guest status and return
> TDX-specific CC attributes. To enable use of CC APIs in the TDX guest,
> select ARCH_HAS_CC_PLATFORM in the CONFIG_INTEL_TDX_GUEST case.
> 
> This is a preparatory patch and just creates the framework for adding
> TDX guest specific CC attributes.
> 
> Since is_tdx_guest() function (through cc_platform_has() API) is used in
> the early boot code, disable the instrumentation flags and function
> tracer. This is similar to AMD SEV and cc_platform.c.
> 
> Since intel_cc_platform_has() function only gets triggered when

"... only gets called... "

-- 
Regards/Gruss,
    Boris.

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