From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f70.google.com (mail-it0-f70.google.com [209.85.214.70]) by kanga.kvack.org (Postfix) with ESMTP id C31956B0038 for ; Wed, 7 Sep 2016 10:02:59 -0400 (EDT) Received: by mail-it0-f70.google.com with SMTP id i184so34802671itf.1 for ; Wed, 07 Sep 2016 07:02:59 -0700 (PDT) Received: from NAM02-SN1-obe.outbound.protection.outlook.com (mail-sn1nam02on0073.outbound.protection.outlook.com. [104.47.36.73]) by mx.google.com with ESMTPS id r11si32570543oih.192.2016.09.07.07.02.58 for (version=TLS1 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 07 Sep 2016 07:02:58 -0700 (PDT) Subject: Re: [RFC PATCH v2 01/20] x86: Documentation for AMD Secure Memory Encryption (SME) References: <20160822223529.29880.50884.stgit@tlendack-t1.amdoffice.net> <20160822223539.29880.96739.stgit@tlendack-t1.amdoffice.net> <20160902085045.GG17338@nazgul.tnic> From: Tom Lendacky Message-ID: <3fbb0763-5f9f-6ff7-2266-7478fb12642e@amd.com> Date: Wed, 7 Sep 2016 09:02:38 -0500 MIME-Version: 1.0 In-Reply-To: <20160902085045.GG17338@nazgul.tnic> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Borislav Petkov Cc: linux-arch@vger.kernel.org, linux-efi@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, iommu@lists.linux-foundation.org, =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Arnd Bergmann , Jonathan Corbet , Matt Fleming , Joerg Roedel , Konrad Rzeszutek Wilk , Andrey Ryabinin , Ingo Molnar , Andy Lutomirski , "H. Peter Anvin" , Paolo Bonzini , Alexander Potapenko , Thomas Gleixner , Dmitry Vyukov On 09/02/2016 03:50 AM, Borislav Petkov wrote: > On Mon, Aug 22, 2016 at 05:35:39PM -0500, Tom Lendacky wrote: >> This patch adds a Documenation entry to decribe the AMD Secure Memory >> Encryption (SME) feature. >> >> Signed-off-by: Tom Lendacky >> --- >> Documentation/x86/amd-memory-encryption.txt | 35 +++++++++++++++++++++++++++ >> 1 file changed, 35 insertions(+) >> create mode 100644 Documentation/x86/amd-memory-encryption.txt >> >> diff --git a/Documentation/x86/amd-memory-encryption.txt b/Documentation/x86/amd-memory-encryption.txt >> new file mode 100644 >> index 0000000..f19c555 >> --- /dev/null >> +++ b/Documentation/x86/amd-memory-encryption.txt >> @@ -0,0 +1,35 @@ >> +Secure Memory Encryption (SME) is a feature found on AMD processors. >> + >> +SME provides the ability to mark individual pages of memory as encrypted using >> +the standard x86 page tables. A page that is marked encrpyted will be > > s/encrpyted/encrypted/ Ugh.. I thought I caught all of these. Obviously not. I'll go through all the patches on this. > >> +automatically decrypted when read from DRAM and encrypted when written to >> +DRAM. SME can therefore be used to protect the contents of DRAM from physical >> +attacks on the system. >> + >> +Support for SME can be determined through the CPUID instruction. The CPUID >> +function 0x8000001f reports information related to SME: >> + >> + 0x8000001f[eax]: >> + Bit[0] indicates support for SME >> + 0x8000001f[ebx]: >> + Bit[5:0] pagetable bit number used to enable memory encryption >> + Bit[11:6] reduction in physical address space, in bits, when >> + memory encryption is enabled (this only affects system >> + physical addresses, not guest physical addresses) >> + >> +If support for SME is present, MSR 0xc00100010 (SYS_CFG) can be used to >> +determine if SME is enabled and/or to enable memory encryption: >> + >> + 0xc0010010: >> + Bit[23] 0 = memory encryption features are disabled >> + 1 = memory encryption features are enabled >> + >> +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 (see >> +CPUID information above) will not conflict with the address space resource >> +requirements for the system. If this bit is not set upon Linux startup then >> +Linux itself will not set it and memory encryption will not be possible. >> + >> +SME support is configurable in the kernel through the AMD_MEM_ENCRYPT config >> +option. > > " ... is configurable through CONFIG_AMD_MEM_ENCRYPT." Ok. > >> Additionally, the mem_encrypt=on command line parameter is required >> +to activate memory encryption. > > I think you want to rewrite the logic here to say that people should use > the BIOS option and if none is present for whatever reason, resort to > the alternative "mem_encrypt=on" kernel command line option, no? Yes, I'll work on rewording this section. Thanks, Tom > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org