From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id 35D546B0038 for ; Thu, 4 May 2017 10:18:01 -0400 (EDT) Received: by mail-pf0-f198.google.com with SMTP id e64so10742343pfd.3 for ; Thu, 04 May 2017 07:18:01 -0700 (PDT) Received: from NAM02-BL2-obe.outbound.protection.outlook.com (mail-bl2nam02on0087.outbound.protection.outlook.com. [104.47.38.87]) by mx.google.com with ESMTPS id 1si2252127pgk.12.2017.05.04.07.18.00 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Thu, 04 May 2017 07:18:00 -0700 (PDT) Subject: Re: [PATCH v5 31/32] x86: Add sysfs support for Secure Memory Encryption References: <20170418211612.10190.82788.stgit@tlendack-t1.amdoffice.net> <20170418212212.10190.73484.stgit@tlendack-t1.amdoffice.net> <1498ec98-b19d-c47d-902b-a68870a3f860@intel.com> <20170427072547.GB15297@dhcp-128-65.nay.redhat.com> <1f034974-20e6-b5e9-e6ff-434b634e1522@intel.com> From: Tom Lendacky Message-ID: Date: Thu, 4 May 2017 09:17:48 -0500 MIME-Version: 1.0 In-Reply-To: <1f034974-20e6-b5e9-e6ff-434b634e1522@intel.com> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen , Dave Young Cc: linux-arch@vger.kernel.org, linux-efi@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, x86@kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Thomas Gleixner , Rik van Riel , Brijesh Singh , Toshimitsu Kani , Arnd Bergmann , Jonathan Corbet , Matt Fleming , Joerg Roedel , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Konrad Rzeszutek Wilk , Andrey Ryabinin , Ingo Molnar , "Michael S. Tsirkin" , Andy Lutomirski , "H. Peter Anvin" , Borislav Petkov , Paolo Bonzini , Alexander Potapenko , Larry Woodman , Dmitry Vyukov On 4/27/2017 10:52 AM, Dave Hansen wrote: > On 04/27/2017 12:25 AM, Dave Young wrote: >> On 04/21/17 at 02:55pm, Dave Hansen wrote: >>> On 04/18/2017 02:22 PM, Tom Lendacky wrote: >>>> Add sysfs support for SME so that user-space utilities (kdump, etc.) can >>>> determine if SME is active. >>>> >>>> A new directory will be created: >>>> /sys/kernel/mm/sme/ >>>> >>>> And two entries within the new directory: >>>> /sys/kernel/mm/sme/active >>>> /sys/kernel/mm/sme/encryption_mask >>> >>> Why do they care, and what will they be doing with this information? >> >> Since kdump will copy old memory but need this to know if the old memory >> was encrypted or not. With this sysfs file we can know the previous SME >> status and pass to kdump kernel as like a kernel param. >> >> Tom, have you got chance to try if it works or not? > > What will the kdump kernel do with it though? We kexec() into that > kernel so the SME keys will all be the same, right? So, will the kdump Yes, the SME key will be same after a kexec. > kernel be just setting the encryption bit in the PTE so it can copy the > old plaintext out? Yes, the idea would be to set the encryption bit in the PTE when mapping and copying encrypted pages and not set it for unencrypted pages. > > Why do we need both 'active' and 'encryption_mask'? How could it be > that the hardware-enumerated 'encryption_mask' changes across a kexec()? > We don't need both, I just added the 'encryption mask' entry for information. It won't change across a kexec, I can remove it. 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