linux-kernel - Re: [RFC PATCH v1 09/28] x86/efi: Access EFI data as encrypted when SEV is active

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Date:   Thu, 22 Sep 2016 14:04:27 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Borislav Petkov <bp@...e.de>, Paolo Bonzini <pbonzini@...hat.com>
CC:     Brijesh Singh <brijesh.singh@....com>, <simon.guinot@...uanux.org>,
        <linux-efi@...r.kernel.org>, <kvm@...r.kernel.org>,
        <rkrcmar@...hat.com>, <matt@...eblueprint.co.uk>,
        <linus.walleij@...aro.org>, <linux-mm@...ck.org>,
        <paul.gortmaker@...driver.com>, <hpa@...or.com>,
        <dan.j.williams@...el.com>, <aarcange@...hat.com>,
        <sfr@...b.auug.org.au>, <andriy.shevchenko@...ux.intel.com>,
        <herbert@...dor.apana.org.au>, <bhe@...hat.com>,
        <xemul@...allels.com>, <joro@...tes.org>, <x86@...nel.org>,
        <mingo@...hat.com>, <msalter@...hat.com>,
        <ross.zwisler@...ux.intel.com>, <dyoung@...hat.com>,
        <jroedel@...e.de>, <keescook@...omium.org>, <toshi.kani@....com>,
        <mathieu.desnoyers@...icios.com>, <devel@...uxdriverproject.org>,
        <tglx@...utronix.de>, <mchehab@...nel.org>,
        <iamjoonsoo.kim@....com>, <labbott@...oraproject.org>,
        <tony.luck@...el.com>, <alexandre.bounine@....com>,
        <kuleshovmail@...il.com>, <linux-kernel@...r.kernel.org>,
        <mcgrof@...nel.org>, <linux-crypto@...r.kernel.org>,
        <akpm@...ux-foundation.org>, <davem@...emloft.net>
Subject: Re: [RFC PATCH v1 09/28] x86/efi: Access EFI data as encrypted when
 SEV is active

On 09/22/2016 12:07 PM, Borislav Petkov wrote:
> On Thu, Sep 22, 2016 at 05:05:54PM +0200, Paolo Bonzini wrote:
>> Which paragraph?
> 
> "Linux relies on BIOS to set this bit if BIOS has determined that the
> reduction in the physical address space as a result of enabling memory
> encryption..."
> 
> Basically, you can enable SME in the BIOS and you're all set.

That's not what I mean here.  If the BIOS sets the SMEE bit in the
SYS_CFG msr then, even if the encryption bit is never used, there is
still a reduction in physical address space.

Transparent SME (TSME) will be a BIOS option that will result in the
memory controller performing encryption no matter what. In this case
all data will be encrypted without a reduction in physical address
space.

Thanks,
Tom

>