linux-kernel - Re: [RFC v2-fix-v2 1/1] x86: Introduce generic protected guest abstraction

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Date:   Wed, 2 Jun 2021 17:20:24 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Borislav Petkov <bp@...en8.de>,
        Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Raj Ashok <ashok.raj@...el.com>, linux-kernel@...r.kernel.org,
        Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [RFC v2-fix-v2 1/1] x86: Introduce generic protected guest
 abstraction

On Tue, Jun 01, 2021, Kuppuswamy Sathyanarayanan wrote:
> diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
> index 9c80c68d75b5..1492b0eb29d0 100644
> --- a/arch/x86/include/asm/mem_encrypt.h
> +++ b/arch/x86/include/asm/mem_encrypt.h
> @@ -56,6 +56,8 @@ bool sev_es_active(void);
>  
>  #define __bss_decrypted __section(".bss..decrypted")
>  
> +bool amd_protected_guest_has(unsigned long flag);


Why call one by the vendor (amd) and the other by the technology (tdx)?
sev_protected_guest_has() seems like the more logical name, e.g. if AMD CPUs
gain a new non-SEV technology then we'll have a mess.

> diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> index f0c1912837c8..cbfe7479f2a3 100644
> --- a/arch/x86/include/asm/tdx.h
> +++ b/arch/x86/include/asm/tdx.h
> @@ -71,6 +71,8 @@ u64 __tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
>  u64 __tdx_hypercall(u64 fn, u64 r12, u64 r13, u64 r14, u64 r15,
>  		    struct tdx_hypercall_output *out);
>  
> +bool tdx_protected_guest_has(unsigned long flag);

...

> +static inline bool protected_guest_has(unsigned long flag)
> +{
> +	if (is_tdx_guest())
> +		return tdx_protected_guest_has(flag);
> +	else if (mem_encrypt_active())

Shouldn't this be sev_active()?  mem_encrypt_active() will return true for SME,
too.

> +		return amd_protected_guest_has(flag);
> +
> +	return false;
> +}