From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f199.google.com (mail-qt0-f199.google.com [209.85.216.199]) by kanga.kvack.org (Postfix) with ESMTP id CDAD76B0069 for ; Tue, 22 Nov 2016 15:41:37 -0500 (EST) Received: by mail-qt0-f199.google.com with SMTP id l20so16392020qta.3 for ; Tue, 22 Nov 2016 12:41:37 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id j123si17394373qkf.105.2016.11.22.12.41.36 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 22 Nov 2016 12:41:37 -0800 (PST) Date: Tue, 22 Nov 2016 22:41:30 +0200 From: "Michael S. Tsirkin" Subject: Re: [RFC PATCH v3 13/20] x86: DMA support for memory encryption Message-ID: <20161122224005-mutt-send-email-mst@kernel.org> 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> <20161122154137.z5vp3xcl5cpesuiz@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161122154137.z5vp3xcl5cpesuiz@pd.tnic> Sender: owner-linux-mm@kvack.org List-ID: To: Borislav Petkov 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 On Tue, Nov 22, 2016 at 04:41:37PM +0100, Borislav Petkov wrote: > 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? Or even modify them. Guests generally trust devices since they assume they are under their control. > > 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