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. Perhaps Shahaf can quantify the performance delta? Jason
