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

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Date:   Thu, 8 Sep 2016 08:26:27 -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>, <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 09/07/2016 10:55 AM, Borislav Petkov wrote:
> On Wed, Sep 07, 2016 at 09:30:54AM -0500, Tom Lendacky wrote:
>> _PAGE_ENC is #defined as sme_me_mask and sme_me_mask has already been
>> set (or not set) at this point - so it will be the mask if SME is
>> active or 0 if SME is not active.
> 
> Yeah, I remember :-)
> 
>> sme_early_init() is merely propagating the mask to other structures.
>> Since early_pmd_flags is mainly used in this file (one line in
>> head_64.S is the other place) I felt it best to modify it here. But it
>> can always be moved if you feel that is best.
> 
> Hmm, so would it work then if you stick it in early_pmd_flags'
> definition like you do with the other masks? I.e.,
> 
> pmdval_t early_pmd_flags = __PAGE_KERNEL_LARGE | _PAGE_ENC & ~(_PAGE_GLOBAL | _PAGE_NX);

When does this value get initialized?  Since _PAGE_ENC is #defined to
sme_me_mask, which is not set until the boot process begins, I'm afraid
we'd end up using the initial value of sme_me_mask, which is zero.  Do
I have that right?

Thanks,
Tom

>