linux-kernel - Re: [PATCH v5 29/32] x86/mm: Add support to encrypt the kernel in-place

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Date:   Fri, 26 May 2017 18:25:22 +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,
        kexec@...ts.infradead.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>,
        Toshimitsu Kani <toshi.kani@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Larry Woodman <lwoodman@...hat.com>,
        Brijesh Singh <brijesh.singh@....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>,
        Dave Young <dyoung@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v5 29/32] x86/mm: Add support to encrypt the kernel
 in-place

On Thu, May 25, 2017 at 05:24:27PM -0500, Tom Lendacky wrote:
> I guess I could do that, but this will probably only end up clearing a
> single PGD entry anyway since it's highly doubtful the address range
> would cross a 512GB boundary.

Or you can compute how many 512G-covering, i.e., PGD entries there are
and clear just the right amnount. :^)

> I can change the name. As for the use of ENTRY... without the
> ENTRY/ENDPROC combination I was receiving a warning about a return
> instruction outside of a callable function. It looks like I can just
> define the "sme_enc_routine:" label with the ENDPROC and the warning
> goes away and the global is avoided. It doesn't like the local labels
> (.L...) so I'll use the new name.

Is that warning from objtool or where does it come from?

How do I trigger it locally?

> The hardware will try to optimize rep movsb into large chunks assuming
> things are aligned, sizes are large enough, etc. so we don't have to
> explicitly specify and setup for a rep movsq.

I thought the hw does that for movsq too?

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.