linux-kernel - Re: [PATCHv3 13/32] x86/tdx: Detect TDX at early kernel decompression time

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Message-ID: <YhN5edJQ+LkVc0us@grain>
Date:   Mon, 21 Feb 2022 14:37:29 +0300
From:   Cyrill Gorcunov <gorcunov@...il.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        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: [PATCHv3 13/32] x86/tdx: Detect TDX at early kernel
 decompression time

On Fri, Feb 18, 2022 at 07:16:59PM +0300, Kirill A. Shutemov wrote:
...
> 
> +
> +void early_tdx_detect(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;

Maybe worth to guard ourself, like

	BUILD_BUG_ON(sizeof(sig) != (sizeof(TDX_IDENT)-1));
	if (memcmp(TDX_IDENT, sig, sizeof(sig))
		return;