From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f197.google.com (mail-qt0-f197.google.com [209.85.216.197]) by kanga.kvack.org (Postfix) with ESMTP id 0D8156B02E1 for ; Fri, 28 Apr 2017 01:33:04 -0400 (EDT) Received: by mail-qt0-f197.google.com with SMTP id i18so11804615qte.1 for ; Thu, 27 Apr 2017 22:33:04 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id l14si5296867qtb.91.2017.04.27.22.33.02 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 27 Apr 2017 22:33:03 -0700 (PDT) Date: Fri, 28 Apr 2017 13:32:33 +0800 From: Dave Young Subject: Re: [PATCH v5 31/32] x86: Add sysfs support for Secure Memory Encryption Message-ID: <20170428053233.GA6149@dhcp-128-65.nay.redhat.com> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1f034974-20e6-b5e9-e6ff-434b634e1522@intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: Tom Lendacky , 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 , Radim =?utf-8?B?S3LEjW3DocWZ?= , 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 04/27/17 at 08:52am, 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 > kernel be just setting the encryption bit in the PTE so it can copy the > old plaintext out? I assume it is for active -> non active case, the new boot need to know the old memory is encrypted. But I think I did not read all the patches I may miss things. > > Why do we need both 'active' and 'encryption_mask'? How could it be > that the hardware-enumerated 'encryption_mask' changes across a kexec()? Leave this question to Tom.. Thanks Dave -- 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