linux-kernel - Re: [PATCH v2 02/12] mm: Introduce a function to check for virtualization protection features

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Message-ID: <YRgMUHqdH60jDB06@zn.tnic>
Date:   Sat, 14 Aug 2021 20:32:48 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        iommu@...ts.linux-foundation.org, kvm@...r.kernel.org,
        linux-efi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-graphics-maintainer@...are.com,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        kexec@...ts.infradead.org, linux-fsdevel@...r.kernel.org,
        Brijesh Singh <brijesh.singh@....com>,
        Joerg Roedel <joro@...tes.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH v2 02/12] mm: Introduce a function to check for
 virtualization protection features

On Fri, Aug 13, 2021 at 11:59:21AM -0500, Tom Lendacky wrote:
> In prep for other protected virtualization technologies, introduce a
> generic helper function, prot_guest_has(), that can be used to check
> for specific protection attributes, like memory encryption. This is
> intended to eliminate having to add multiple technology-specific checks
> to the code (e.g. if (sev_active() || tdx_active())).
> 
> Reviewed-by: Joerg Roedel <jroedel@...e.de>
> Co-developed-by: Andi Kleen <ak@...ux.intel.com>
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> Co-developed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
> ---
>  arch/Kconfig                    |  3 +++
>  include/linux/protected_guest.h | 35 +++++++++++++++++++++++++++++++++
>  2 files changed, 38 insertions(+)
>  create mode 100644 include/linux/protected_guest.h
> 
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 98db63496bab..bd4f60c581f1 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -1231,6 +1231,9 @@ config RELR
>  config ARCH_HAS_MEM_ENCRYPT
>  	bool
>  
> +config ARCH_HAS_PROTECTED_GUEST
> +	bool
> +
>  config HAVE_SPARSE_SYSCALL_NR
>         bool
>         help
> diff --git a/include/linux/protected_guest.h b/include/linux/protected_guest.h
> new file mode 100644
> index 000000000000..43d4dde94793
> --- /dev/null
> +++ b/include/linux/protected_guest.h
> @@ -0,0 +1,35 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Protected Guest (and Host) Capability checks
> + *
> + * Copyright (C) 2021 Advanced Micro Devices, Inc.
> + *
> + * Author: Tom Lendacky <thomas.lendacky@....com>
> + */
> +
> +#ifndef _PROTECTED_GUEST_H
> +#define _PROTECTED_GUEST_H
> +
> +#ifndef __ASSEMBLY__
	   ^^^^^^^^^^^^^

Do you really need that guard? It builds fine without it too. Or
something coming later does need it...?

-- 
Regards/Gruss,
    Boris.

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