linux-kernel - Re: [PATCH v7 19/36] x86/mm: Add support to access boot related data in the clear

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Date:   Thu, 22 Jun 2017 12:04:05 +0100
From:   Matt Fleming <matt@...eblueprint.co.uk>
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, xen-devel@...ts.xen.org,
        linux-mm@...ck.org, iommu@...ts.linux-foundation.org,
        Brijesh Singh <brijesh.singh@....com>,
        Toshimitsu Kani <toshi.kani@....com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Alexander Potapenko <glider@...gle.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Larry Woodman <lwoodman@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Joerg Roedel <joro@...tes.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Dave Young <dyoung@...hat.com>, Rik van Riel <riel@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Juergen Gross <jgross@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v7 19/36] x86/mm: Add support to access boot related data
 in the clear

On Fri, 16 Jun, at 01:53:26PM, Tom Lendacky wrote:
> Boot data (such as EFI related data) is not encrypted when the system is
> booted because UEFI/BIOS does not run with SME active. In order to access
> this data properly it needs to be mapped decrypted.
> 
> Update early_memremap() to provide an arch specific routine to modify the
> pagetable protection attributes before they are applied to the new
> mapping. This is used to remove the encryption mask for boot related data.
> 
> Update memremap() to provide an arch specific routine to determine if RAM
> remapping is allowed.  RAM remapping will cause an encrypted mapping to be
> generated. By preventing RAM remapping, ioremap_cache() will be used
> instead, which will provide a decrypted mapping of the boot related data.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
> ---
>  arch/x86/include/asm/io.h |    5 +
>  arch/x86/mm/ioremap.c     |  179 +++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/io.h        |    2 +
>  kernel/memremap.c         |   20 ++++-
>  mm/early_ioremap.c        |   18 ++++-
>  5 files changed, 217 insertions(+), 7 deletions(-)

Reviewed-by: Matt Fleming <matt@...eblueprint.co.uk>