linux-kernel - Re: [RFC PATCH v2 07/20] x86: Provide general kernel support for memory encryption

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Date:   Mon, 5 Sep 2016 17:22:12 +0200
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,
        Radim Krčmář <rkrcmar@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Joerg Roedel <joro@...tes.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Alexander Potapenko <glider@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [RFC PATCH v2 07/20] x86: Provide general kernel support for
 memory encryption

On Mon, Aug 22, 2016 at 05:36:46PM -0500, Tom Lendacky wrote:
> Adding general kernel support for memory encryption includes:
> - Modify and create some page table macros to include the Secure Memory
>   Encryption (SME) memory encryption mask
> - Update kernel boot support to call an SME routine that checks for and
>   sets the SME capability (the SME routine will grow later and for now
>   is just a stub routine)
> - Update kernel boot support to call an SME routine that encrypts the
>   kernel (the SME routine will grow later and for now is just a stub
>   routine)
> - Provide an SME initialization routine to update the protection map with
>   the memory encryption mask so that it is used by default
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>

...

> diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
> index c98a559..30f7715 100644
> --- a/arch/x86/kernel/head_64.S
> +++ b/arch/x86/kernel/head_64.S
> @@ -95,6 +95,13 @@ startup_64:
>  	jnz	bad_address
>  
>  	/*
> +	 * Enable memory encryption (if available). Add the memory encryption
> +	 * mask to %rbp to include it in the the page table fixup.
> +	 */
> +	call	sme_enable
> +	addq	sme_me_mask(%rip), %rbp
> +
> +	/*
>  	 * Fixup the physical addresses in the page table
>  	 */
>  	addq	%rbp, early_level4_pgt + (L4_START_KERNEL*8)(%rip)
> @@ -116,7 +123,8 @@ startup_64:
>  	movq	%rdi, %rax
>  	shrq	$PGDIR_SHIFT, %rax
>  
> -	leaq	(4096 + _KERNPG_TABLE)(%rbx), %rdx
> +	leaq	(4096 + __KERNPG_TABLE)(%rbx), %rdx
> +	addq	sme_me_mask(%rip), %rdx		/* Apply mem encryption mask */

Please add comments over the line and not at the side...

-- 
Regards/Gruss,
    Boris.

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