From mboxrd@z Thu Jan 1 00:00:00 1970 From: Borislav Petkov Subject: Re: [RFC PATCH v3 13/20] x86: DMA support for memory encryption Date: Tue, 22 Nov 2016 16:41:37 +0100 Message-ID: <20161122154137.z5vp3xcl5cpesuiz@pd.tnic> References: <20161110003426.3280.2999.stgit@tlendack-t1.amdoffice.net> <20161110003723.3280.62636.stgit@tlendack-t1.amdoffice.net> <20161115171443-mutt-send-email-mst@kernel.org> <4d97f998-5835-f4e0-9840-7f7979251275@amd.com> <20161122113859.5dtlrfgizwpum6st@pd.tnic> <20161122171455-mutt-send-email-mst@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Return-path: Content-Disposition: inline In-Reply-To: <20161122171455-mutt-send-email-mst@kernel.org> Sender: owner-linux-mm@kvack.org To: "Michael S. Tsirkin" 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, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Rik van Riel , Radim =?utf-8?B?S3LEjW3DocWZ?= , Arnd Bergmann , Jonathan Corbet , Matt Fleming , Joerg Roedel , Konrad Rzeszutek Wilk , Paolo Bonzini , Larry Woodman , Ingo Molnar , Andy Lutomirski , "H. Peter Anvin" , Andrey Ryabinin , Alexander Potapenko , Thomas Gleixner , Dmitry Vyukov List-Id: linux-arch.vger.kernel.org On Tue, Nov 22, 2016 at 05:22:38PM +0200, Michael S. Tsirkin wrote: > The issue is it's a (potential) security hole, not a slowdown. How? Because the bounce buffers will be unencrypted and someone might intercept them? > To disable unsecure things. If someone enables SEV one might have an > expectation of security. Might help push vendors to do the right thing > as a side effect. Ok, you're looking at the SEV-cloud-multiple-guests aspect. Right, that makes sense. I guess for SEV we should even flip the logic: disable such devices by default and an opt-in option to enable them and issue a big fat warning. I'd even want to let the guest users know that they're on a system which cannot give them encrypted DMA to some devices... -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply. -- 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.skyhub.de ([78.46.96.112]:44345 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755105AbcKVPnh (ORCPT ); Tue, 22 Nov 2016 10:43:37 -0500 Date: Tue, 22 Nov 2016 16:41:37 +0100 From: Borislav Petkov Subject: Re: [RFC PATCH v3 13/20] x86: DMA support for memory encryption Message-ID: <20161122154137.z5vp3xcl5cpesuiz@pd.tnic> References: <20161110003426.3280.2999.stgit@tlendack-t1.amdoffice.net> <20161110003723.3280.62636.stgit@tlendack-t1.amdoffice.net> <20161115171443-mutt-send-email-mst@kernel.org> <4d97f998-5835-f4e0-9840-7f7979251275@amd.com> <20161122113859.5dtlrfgizwpum6st@pd.tnic> <20161122171455-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20161122171455-mutt-send-email-mst@kernel.org> Sender: linux-arch-owner@vger.kernel.org List-ID: To: "Michael S. Tsirkin" 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, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Rik van Riel , Radim =?utf-8?B?S3LEjW3DocWZ?= , Arnd Bergmann , Jonathan Corbet , Matt Fleming , Joerg Roedel , Konrad Rzeszutek Wilk , Paolo Bonzini , Larry Woodman , Ingo Molnar , Andy Lutomirski , "H. Peter Anvin" , Andrey Ryabinin , Alexander Potapenko , Thomas Gleixner , Dmitry Vyukov Message-ID: <20161122154137.D8OJciOJBV30JgBQoPgCGFy0ifp4vf3-3AxeDLmwico@z> On Tue, Nov 22, 2016 at 05:22:38PM +0200, Michael S. Tsirkin wrote: > The issue is it's a (potential) security hole, not a slowdown. How? Because the bounce buffers will be unencrypted and someone might intercept them? > To disable unsecure things. If someone enables SEV one might have an > expectation of security. Might help push vendors to do the right thing > as a side effect. Ok, you're looking at the SEV-cloud-multiple-guests aspect. Right, that makes sense. I guess for SEV we should even flip the logic: disable such devices by default and an opt-in option to enable them and issue a big fat warning. I'd even want to let the guest users know that they're on a system which cannot give them encrypted DMA to some devices... -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply.