linux-kernel - Re: [PATCHv2 01/29] x86/tdx: Detect running as a TDX guest in early boot

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Message-ID: <87fsp2z8p8.ffs@tglx>
Date:   Tue, 01 Feb 2022 20:29:55 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...el.com,
        luto@...nel.org, peterz@...radead.org
Cc:     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,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCHv2 01/29] x86/tdx: Detect running as a TDX guest in early
 boot

Kirill,

On Mon, Jan 24 2022 at 18:01, Kirill A. Shutemov wrote:

Just a nitpick...

> +static bool tdx_guest_detected __ro_after_init;
> +
> +bool is_tdx_guest(void)
> +{
> +	return tdx_guest_detected;
> +}
> +
> +void __init tdx_early_init(void)
> +{
> +	u32 eax, sig[3];
> +
> +	cpuid_count(TDX_CPUID_LEAF_ID, 0, &eax, &sig[0], &sig[2],  &sig[1]);
> +
> +	if (memcmp(TDX_IDENT, sig, 12))
> +		return;
> +
> +	tdx_guest_detected = true;
> +
> +	setup_force_cpu_cap(X86_FEATURE_TDX_GUEST);

So with that we have two ways to detect a TDX guest:

   - tdx_guest_detected

   - X86_FEATURE_TDX_GUEST

Shouldn't X86_FEATURE_TDX_GUEST be good enough?

Thanks,

        tglx