linux-kernel - Re: [PATCH v10 04/11] x86/tdx: Add TDX support to intel_cc_platform

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Date:   Thu, 14 Oct 2021 09:12:56 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        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>
Cc:     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>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10 04/11] x86/tdx: Add TDX support to
 intel_cc_platform_has()

On Fri, Oct 08 2021 at 22:37, Kuppuswamy Sathyanarayanan wrote:
>  
> -static bool __maybe_unused intel_cc_platform_has(enum cc_attr attr)
> +static bool intel_cc_platform_has(enum cc_attr attr)
>  {
>  #ifdef CONFIG_INTEL_TDX_GUEST
> -	return false;
> +	switch (attr) {
> +	case CC_ATTR_GUEST_TDX:
> +		return is_tdx_guest();

This function is only called when is_tdx_guest() is true. So
is_tdx_guest() has to be called again to make sure?

Also the ifdeffery can just go away simply because the compiler will
discard this function when CONFIG_INTEL_TDX_GUEST=n due to:

> +#ifdef CONFIG_INTEL_TDX_GUEST
> +
> +bool is_tdx_guest(void);
> +void __init tdx_early_init(void);
> +
> +#else
> +
> +static inline bool is_tdx_guest(void) { return false; }
> +static inline void tdx_early_init(void) { };
> +
> +#endif /* CONFIG_INTEL_TDX_GUEST */

Thanks,

        tglx