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

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Message-ID: <20160902181447.GA25328@nazgul.tnic>
Date:   Fri, 2 Sep 2016 20:14:47 +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/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
> index 747fc52..9f3e762 100644
> --- a/arch/x86/include/asm/mem_encrypt.h
> +++ b/arch/x86/include/asm/mem_encrypt.h
> @@ -15,12 +15,21 @@
>  
>  #ifndef __ASSEMBLY__
>  
> +#include <linux/init.h>
> +
>  #ifdef CONFIG_AMD_MEM_ENCRYPT
>  
>  extern unsigned long sme_me_mask;
>  
>  u8 sme_get_me_loss(void);
>  
> +void __init sme_early_init(void);
> +
> +#define __sme_pa(x)		(__pa((x)) | sme_me_mask)
> +#define __sme_pa_nodebug(x)	(__pa_nodebug((x)) | sme_me_mask)
> +
> +#define __sme_va(x)		(__va((x) & ~sme_me_mask))

So I'm wondering: why not push the masking off of the SME mask into the
__va() macro instead of defining a specific __sme_va() one?

I mean, do you even see cases where __va() would need to have to
sme_mask left in the virtual address?

Because if not, you could mask it out in __va() so that all __va() users
get the "clean" va, without the enc bits.

Hmmm.

Btw, this patch is huuuge. It would be nice if you could split it, if
possible...

Thanks.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
--