linux-kernel - Re: [RFC PATCH v3 04/20] x86: Handle reduction in physical address size with SME

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Message-ID: <20161115153338.a2cxmatnpqcgiaiy@pd.tnic>
Date:   Tue, 15 Nov 2016 16:33:39 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     Joerg Roedel <joro@...tes.org>, 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>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Larry Woodman <lwoodman@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [RFC PATCH v3 04/20] x86: Handle reduction in physical address
 size with SME

On Tue, Nov 15, 2016 at 08:40:05AM -0600, Tom Lendacky wrote:
> The feature may be present and enabled even if it is not currently
> active.  In other words, the SYS_CFG MSR bit could be set but we aren't
> actually using encryption (sme_me_mask is 0).  As long as the SYS_CFG
> MSR bit is set we need to take into account the physical reduction in
> address space.

But later in the series I see sme_early_mem_enc() which tests exactly
that mask.

And in patch 12 you have:

+       /*
+        * If memory encryption is active, the trampoline area will need to
+        * be in un-encrypted memory in order to bring up other processors
+        * successfully.
+        */
+       sme_early_mem_dec(__pa(base), size);
+       sme_set_mem_unenc(base, size);

What's up?

IOW, it all sounds to me like you want to have an sme_active() helper
and use it everywhere.

-- 
Regards/Gruss,
    Boris.

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