linux-kernel - Re: [PATCH v5 06/32] x86/mm: Add Secure Memory Encryption (SME) support

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Message-ID: <6d266f5b-c28d-fe19-24b5-5133532f9eea@amd.com>
Date:   Tue, 16 May 2017 14:28:42 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Borislav Petkov <bp@...en8.de>
CC:     <linux-arch@...r.kernel.org>, <linux-efi@...r.kernel.org>,
        <kvm@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <x86@...nel.org>, <kexec@...ts.infradead.org>,
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        Rik van Riel <riel@...hat.com>,
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        Toshimitsu Kani <toshi.kani@....com>,
        Arnd Bergmann <arnd@...db.de>,
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        Thomas Gleixner <tglx@...utronix.de>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v5 06/32] x86/mm: Add Secure Memory Encryption (SME)
 support

On 5/4/2017 9:36 AM, Borislav Petkov wrote:
> On Thu, May 04, 2017 at 09:24:11AM -0500, Tom Lendacky wrote:
>> I did this so that an the include order wouldn't cause issues (including
>> asm/mem_encrypt.h followed by later by a linux/mem_encrypt.h include).
>> I can make this a bit clearer by having separate #defines for each
>> thing, e.g.:
>>
>> #ifndef sme_me_mask
>> #define sme_me_mask 0UL
>> #endif
>>
>> #ifndef sme_active
>> #define sme_active sme_active
>> static inline ...
>> #endif
>>
>> Is that better/clearer?
>
> I guess but where do we have to include both the asm/ and the linux/
> version?

It's more of the sequence of various includes.  For example,
init/do_mounts.c includes <linux/module.h> that eventually gets down
to <asm/pgtable_types.h> and then <asm/mem_encrypt.h>.  However, a
bit further down <linux/nfs_fs.h> is included which eventually gets
down to <linux/dma-mapping.h> and then <linux/mem_encyrpt.h>.

>
> IOW, can we avoid these issues altogether by partitioning symbol
> declarations differently among the headers?

It's most problematic when CONFIG_AMD_MEM_ENCRYPT is not defined since
we never include an asm/ version from the linux/ path.  I could create
a mem_encrypt.h in include/asm-generic/ that contains the info that
is in the !CONFIG_AMD_MEM_ENCRYPT path of the linux/ version. Let me
look into that.

Thanks,
Tom

>