linux-kernel - Re: [PATCH v3 04/11] x86: Introduce generic protected guest abstraction

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Message-ID: <YNSeZv/U6QKK8sBo@zn.tnic>
Date:   Thu, 24 Jun 2021 17:01:58 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        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>,
        Sean Christopherson <seanjc@...gle.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 04/11] x86: Introduce generic protected guest
 abstraction

On Fri, Jun 18, 2021 at 03:57:48PM -0700, Kuppuswamy Sathyanarayanan wrote:
> Add a generic way to check if we run with an encrypted guest,

Please use passive voice in your commit message: no "we" or "I", etc,
and describe your changes in imperative mood.

Also, pls read section "2) Describe your changes" in
Documentation/process/submitting-patches.rst for more details.

Bottom line is: personal pronouns are ambiguous in text, especially with
so many parties/companies/etc developing the kernel so let's avoid them
please.

> without requiring x86 specific ifdefs. This can then be used in
> non architecture specific code. 

"... in arch-independent code." or so.

> prot_guest_has() is used to check for protected guest feature
> flags.
> 
> Originally-by: Andi Kleen <ak@...ux.intel.com>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> ---
> 
> Change since v1:
>  * Introduced PR_GUEST_TDX and PR_GUEST_SEV vendor flags as per
>    Boris suggestion.
>  * Replaced is_tdx_guest() with if (boot_cpu_data.x86_vendor ==
>    X86_VENDOR_INTEL) in prot_guest_has().
>  * Modified tdx_protected_guest_has() and sev_protected_guest_has()
>    to support vendor flags.

...

> diff --git a/arch/x86/include/asm/protected_guest.h b/arch/x86/include/asm/protected_guest.h
> new file mode 100644
> index 000000000000..d47668dee6c2
> --- /dev/null
> +++ b/arch/x86/include/asm/protected_guest.h
> @@ -0,0 +1,20 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/* Copyright (C) 2020 Intel Corporation */
> +#ifndef _ASM_PROTECTED_GUEST_H
> +#define _ASM_PROTECTED_GUEST_H 1

#define _ASM_X86_PROTECTED_GUEST_H

> +
> +#include <asm/processor.h>
> +#include <asm/tdx.h>
> +#include <asm/sev.h>
> +
> +static inline bool prot_guest_has(unsigned long flag)
> +{
> +	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
> +		return tdx_protected_guest_has(flag);
> +	else if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
> +		return sev_protected_guest_has(flag);

s/protected/prot/

tdx_prot_guest_has
sev_prot_guest_has

...

> @@ -18,6 +20,21 @@ static inline bool cpuid_has_tdx_guest(void)
>  	return !memcmp("IntelTDX    ", sig, 12);
>  }
>  
> +bool tdx_protected_guest_has(unsigned long flag)
> +{
> +	switch (flag) {
> +	case PR_GUEST_MEM_ENCRYPT:
> +	case PR_GUEST_MEM_ENCRYPT_ACTIVE:
> +	case PR_GUEST_UNROLL_STRING_IO:
> +	case PR_GUEST_SHARED_MAPPING_INIT:
> +	case PR_GUEST_TDX:
> +		return static_cpu_has(X86_FEATURE_TDX_GUEST);

		return cpu_feature_enabled(...)


-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette