From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-bl2nam02on0079.outbound.protection.outlook.com ([104.47.38.79] helo=NAM02-BL2-obe.outbound.protection.outlook.com) by bombadil.infradead.org with esmtps (Exim 4.87 #1 (Red Hat Linux)) id 1d6HaG-00065G-Ue for kexec@lists.infradead.org; Thu, 04 May 2017 14:18:22 +0000 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> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Dave Hansen , Dave Young Cc: linux-efi@vger.kernel.org, Brijesh Singh , Toshimitsu Kani , linux-doc@vger.kernel.org, Matt Fleming , linux-mm@kvack.org, =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Alexander Potapenko , "H. Peter Anvin" , Larry Woodman , linux-arch@vger.kernel.org, kvm@vger.kernel.org, Jonathan Corbet , Joerg Roedel , x86@kernel.org, kasan-dev@googlegroups.com, Ingo Molnar , Andrey Ryabinin , Rik van Riel , Arnd Bergmann , Konrad Rzeszutek Wilk , Borislav Petkov , Andy Lutomirski , Thomas Gleixner , Dmitry Vyukov , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, "Michael S. Tsirkin" , Paolo Bonzini 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 _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec