From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [RFC PATCH] virtio_ring: Use DMA API if guest memory is encrypted Date: Wed, 30 Jan 2019 08:44:27 +0100 Message-ID: <20190130074427.GA29516@lst.de> References: <87zhrj8kcp.fsf@morokweng.localdomain> <87womn8inf.fsf@morokweng.localdomain> <20190129134750-mutt-send-email-mst@kernel.org> <6c68f7f7-1b28-6eba-9b8b-2c32efac9701@redhat.com> <20190129213137-mutt-send-email-mst@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20190129213137-mutt-send-email-mst@kernel.org> Sender: linux-kernel-owner@vger.kernel.org To: "Michael S. Tsirkin" Cc: Jason Wang , Thiago Jung Bauermann , virtualization@lists.linux-foundation.org, linuxppc-dev@lists.ozlabs.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Christoph Hellwig , David Gibson , Alexey Kardashevskiy , Paul Mackerras , Benjamin Herrenschmidt , Ram Pai , Jean-Philippe Brucker List-Id: iommu@lists.linux-foundation.org On Tue, Jan 29, 2019 at 09:36:08PM -0500, Michael S. Tsirkin wrote: > This has been discussed ad nauseum. virtio is all about compatibility. > Losing a couple of lines of code isn't worth breaking working setups. > People that want "just use DMA API no tricks" now have the option. > Setting a flag in a feature bit map is literally a single line > of code in the hypervisor. So stop pushing for breaking working > legacy setups and just fix it in the right place. I agree with the legacy aspect. What I am missing is an extremely strong wording that says you SHOULD always set this flag for new hosts, including an explanation why.