linux-kernel - Re: [RFC PATCH v2 11/20] mm: Access BOOT related data in the clear

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Message-ID: <e30ddb53-df6c-28ee-54fe-f3e52e515acb@amd.com>
Date:   Wed, 14 Sep 2016 09:20:44 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Andy Lutomirski <luto@...capital.net>,
        Matt Fleming <mfleming@...e.de>
CC:     kasan-dev <kasan-dev@...glegroups.com>,
        "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        <iommu@...ts.linux-foundation.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Alexander Potapenko <glider@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Arnd Bergmann <arnd@...db.de>, Joerg Roedel <joro@...tes.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        "H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
        kvm list <kvm@...r.kernel.org>
Subject: Re: [RFC PATCH v2 11/20] mm: Access BOOT related data in the clear

On 09/12/2016 11:55 AM, Andy Lutomirski wrote:
> On Aug 22, 2016 6:53 PM, "Tom Lendacky" <thomas.lendacky@....com> wrote:
>>
>> BOOT data (such as EFI related data) is not encyrpted when the system is
>> booted and needs to be accessed as non-encrypted.  Add support to the
>> early_memremap API to identify the type of data being accessed so that
>> the proper encryption attribute can be applied.  Currently, two types
>> of data are defined, KERNEL_DATA and BOOT_DATA.
> 
> What happens when you memremap boot services data outside of early
> boot?  Matt just added code that does this.
> 
> IMO this API is not so great.  It scatters a specialized consideration
> all over the place.  Could early_memremap not look up the PA to figure
> out what to do?

Yes, I could see if the PA falls outside of the kernel usable area and,
if so, remove the memory encryption attribute from the mapping (for both
early_memremap and memremap).

Let me look into that, I would prefer something along that line over
this change.

Thanks,
Tom

> 
> --Andy
>