From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH 3/5] vDPA: introduce vDPA bus Date: Tue, 21 Jan 2020 09:16:02 -0500 Message-ID: <20200121091540-mutt-send-email-mst@kernel.org> References: <20200116124231.20253-4-jasowang@redhat.com> <20200117070324-mutt-send-email-mst@kernel.org> <239b042c-2d9e-0eec-a1ef-b03b7e2c5419@redhat.com> <20200120174933.GB3891@mellanox.com> <20200120162449-mutt-send-email-mst@kernel.org> <20200121140755.GB12330@mellanox.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20200121140755.GB12330@mellanox.com> Sender: linux-kernel-owner@vger.kernel.org To: Jason Gunthorpe Cc: Shahaf Shuler , Jason Wang , Rob Miller , "linux-kernel@vger.kernel.org" , "kvm@vger.kernel.org" , "virtualization@lists.linux-foundation.org" , Netdev , "Bie, Tiwei" , "maxime.coquelin@redhat.com" , "Liang, Cunming" , "Wang, Zhihong" , "Wang, Xiao W" , "haotian.wang@sifive.com" , "Zhu, Lingshan" , "eperezma@redhat.com" , "lulu@redhat.com" , Parav Pandit List-Id: virtualization@lists.linuxfoundation.org On Tue, Jan 21, 2020 at 02:07:59PM +0000, Jason Gunthorpe wrote: > On Mon, Jan 20, 2020 at 04:25:23PM -0500, Michael S. Tsirkin wrote: > > On Mon, Jan 20, 2020 at 08:51:43PM +0000, Shahaf Shuler wrote: > > > Monday, January 20, 2020 7:50 PM, Jason Gunthorpe: > > > > Subject: Re: [PATCH 3/5] vDPA: introduce vDPA bus > > > > > > > > On Mon, Jan 20, 2020 at 04:43:53PM +0800, Jason Wang wrote: > > > > > This is similar to the design of platform IOMMU part of vhost-vdpa. We > > > > > decide to send diffs to platform IOMMU there. If it's ok to do that in > > > > > driver, we can replace set_map with incremental API like map()/unmap(). > > > > > > > > > > Then driver need to maintain rbtree itself. > > > > > > > > I think we really need to see two modes, one where there is a fixed > > > > translation without dynamic vIOMMU driven changes and one that supports > > > > vIOMMU. > > > > > > > > There are different optimization goals in the drivers for these two > > > > configurations. > > > > > > +1. > > > It will be best to have one API for static config (i.e. mapping can be > > > set only before virtio device gets active), and one API for dynamic > > > changes that can be set after the virtio device is active. > > > > Frankly I don't see when we'd use the static one. > > Memory hotplug is enabled for most guests... > > If someone wants to run a full performance application, like dpdk, > then they may wish to trade memory hotplug in that VM for more > performance. Right. But let let's get basic functionality working first. > Perhaps Shahaf can quantify the performance delta? > > Jason