linux-kernel - Re: [PATCH v1 03/11] x86/cpufeatures: Add TDX Guest CPU feature

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Date:   Mon, 7 Jun 2021 09:32:28 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.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>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v1 03/11] x86/cpufeatures: Add TDX Guest CPU feature

On 6/1/21 9:21 PM, Kuppuswamy Sathyanarayanan wrote:
> Add CPU feature detection for Trusted Domain Extensions support.
> TDX feature adds capabilities to keep guest register state and
> memory isolated from hypervisor.
> 
> For TDX guest platforms, executing CPUID(0x21, 0) will return
> following values in EAX, EBX, ECX and EDX.
> 
> EAX:  Maximum sub-leaf number:  0
> EBX/EDX/ECX:  Vendor string:
> 
> EBX =  "Inte"
> EDX =  "lTDX"
> ECX =  "    "
> 
> So when above condition is true, set X86_FEATURE_TDX_GUEST
> feature cap bit
> 
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> Reviewed-by: Andi Kleen <ak@...ux.intel.com>
> Reviewed-by: Tony Luck <tony.luck@...el.com>
> ---

...

>  /*
>   * Manage page tables very early on.
> @@ -491,6 +492,8 @@ asmlinkage __visible void __init x86_64_start_kernel(char * real_mode_data)
>  
>  	kasan_early_init();
>  
> +	tdx_early_init();
> +

Just a real minor nit, but does this have to be after kasan_early_init()?
If not, keeping the SME/SEV/TDX calls "together" might read clearer. So
just moving it up before kasan_early_init() will group them.

Thanks,
Tom