linux-kernel - Re: [PATCH v3 3/8] x86/sev: Add an x86 version of cc_platform

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Message-ID: <YTyAhmPf39Vqd7G9@zn.tnic>
Date:   Sat, 11 Sep 2021 12:10:14 +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>,
        Christoph Hellwig <hch@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v3 3/8] x86/sev: Add an x86 version of cc_platform_has()

On Wed, Sep 08, 2021 at 05:58:34PM -0500, Tom Lendacky wrote:
> diff --git a/arch/x86/kernel/cc_platform.c b/arch/x86/kernel/cc_platform.c
> new file mode 100644
> index 000000000000..3c9bacd3c3f3
> --- /dev/null
> +++ b/arch/x86/kernel/cc_platform.c
> @@ -0,0 +1,21 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Confidential Computing Platform Capability checks
> + *
> + * Copyright (C) 2021 Advanced Micro Devices, Inc.
> + *
> + * Author: Tom Lendacky <thomas.lendacky@....com>
> + */
> +
> +#include <linux/export.h>
> +#include <linux/cc_platform.h>
> +#include <linux/mem_encrypt.h>
> +
> +bool cc_platform_has(enum cc_attr attr)
> +{
> +	if (sme_me_mask)

Why are you still checking the sme_me_mask here? AFAIR, we said that
we'll do that only when the KVM folks come with a valid use case...

> +		return amd_cc_platform_has(attr);
> +
> +	return false;
> +}
> +EXPORT_SYMBOL_GPL(cc_platform_has);
> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
> index ff08dc463634..18fe19916bc3 100644
> --- a/arch/x86/mm/mem_encrypt.c
> +++ b/arch/x86/mm/mem_encrypt.c
> @@ -20,6 +20,7 @@
>  #include <linux/bitops.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/virtio_config.h>
> +#include <linux/cc_platform.h>
>  
>  #include <asm/tlbflush.h>
>  #include <asm/fixmap.h>
> @@ -389,6 +390,26 @@ bool noinstr sev_es_active(void)
>  	return sev_status & MSR_AMD64_SEV_ES_ENABLED;
>  }
>  
> +bool amd_cc_platform_has(enum cc_attr attr)
> +{
> +	switch (attr) {
> +	case CC_ATTR_MEM_ENCRYPT:
> +		return sme_me_mask != 0;

No need for the "!= 0"

-- 
Regards/Gruss,
    Boris.

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