linux-kernel - Re: [RFC PATCH v4 04/28] x86: Handle reduction in physical address size with SME

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Date:   Fri, 17 Feb 2017 12:04:32 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     linux-arch@...r.kernel.org, linux-efi@...r.kernel.org,
        kvm@...r.kernel.org, linux-doc@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        linux-mm@...ck.org, iommu@...ts.linux-foundation.org,
        Rik van Riel <riel@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Toshimitsu Kani <toshi.kani@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Larry Woodman <lwoodman@...hat.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [RFC PATCH v4 04/28] x86: Handle reduction in physical address
 size with SME

On Thu, Feb 16, 2017 at 09:42:54AM -0600, Tom Lendacky wrote:
> When System Memory Encryption (SME) is enabled, the physical address
> space is reduced. Adjust the x86_phys_bits value to reflect this
> reduction.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
> ---
>  arch/x86/kernel/cpu/common.c |   10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
> index b33bc06..358208d7 100644
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c
> @@ -771,11 +771,15 @@ void get_cpu_cap(struct cpuinfo_x86 *c)
>  			u64 msr;
>  
>  			/*
> -			 * For SME, BIOS support is required. If BIOS has not
> -			 * enabled SME don't advertise the feature.
> +			 * For SME, BIOS support is required. If BIOS has
> +			 * enabled SME adjust x86_phys_bits by the SME
> +			 * physical address space reduction value. If BIOS
> +			 * has not enabled SME don't advertise the feature.
>  			 */
>  			rdmsrl(MSR_K8_SYSCFG, msr);
> -			if (!(msr & MSR_K8_SYSCFG_MEM_ENCRYPT))
> +			if (msr & MSR_K8_SYSCFG_MEM_ENCRYPT)
> +				c->x86_phys_bits -= (ebx >> 6) & 0x3f;
> +			else
>  				eax &= ~0x01;

Right, as I mentioned yesterday, this should go to arch/x86/kernel/cpu/amd.c

-- 
Regards/Gruss,
    Boris.

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