linux-kernel - Re: [PATCH v5 04/12] x86/tdx: Add protected guest support for TDX guest

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Date:   Wed, 4 Aug 2021 21:59:00 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     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>,
        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>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 04/12] x86/tdx: Add protected guest support for TDX
 guest

On Wed, Aug 04, 2021, Kuppuswamy Sathyanarayanan wrote:
> TDX architecture provides a way for VM guests to be highly secure and
> isolated (from untrusted VMM). To achieve this requirement, we can't
> completely trust any data coming from VMM. TDX guest fixes this issue
> by hardening the IO drivers against the attack from the VMM. Since we
> have a requirement to modify the generic drivers, we need to use the
> generic prot_guest_has() API to add TDX specific code in generic
> drivers.
> 
> So add TDX guest support in prot_guest_has() API.
> 
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> ---

...

> diff --git a/arch/x86/include/asm/protected_guest.h b/arch/x86/include/asm/protected_guest.h
> index b4a267dddf93..c67bf13c8ad3 100644
> --- a/arch/x86/include/asm/protected_guest.h
> +++ b/arch/x86/include/asm/protected_guest.h
> @@ -12,12 +12,17 @@
>  
>  #include <linux/mem_encrypt.h>
>  
> +#include <asm/processor.h>
> +#include <asm/tdx.h>
> +
>  #ifndef __ASSEMBLY__
>  
>  static inline bool prot_guest_has(unsigned int attr)
>  {
>  	if (sme_me_mask)
>  		return amd_prot_guest_has(attr);
> +	else if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)

Why not "boot_cpu_has(X86_FEATURE_TDX_GUEST)"?