Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Thomas Gleixner <tglx@linutronix.de>
To:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        mingo@redhat.com, bp@alien8.de, dave.hansen@intel.com,
        luto@kernel.org, peterz@infradead.org
Cc:     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,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCHv2 01/29] x86/tdx: Detect running as a TDX guest in early
 boot
In-Reply-To: <20220124150215.36893-2-kirill.shutemov@linux.intel.com>
References: <20220124150215.36893-1-kirill.shutemov@linux.intel.com>
 <20220124150215.36893-2-kirill.shutemov@linux.intel.com>
Date:   Tue, 01 Feb 2022 20:29:55 +0100
Message-ID: <87fsp2z8p8.ffs@tglx>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

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