Hi Si-Wei: On Sat, Oct 21, 2023 at 5:28 PM Si-Wei Liu <si-wei.liu@xxxxxxxxxx> wrote: > > In order to reduce needlessly high setup and teardown cost > of iotlb mapping during live migration, it's crucial to > decouple the vhost-vdpa iotlb abstraction from the virtio > device life cycle, i.e. iotlb mappings should be left > intact across virtio device reset [1]. For it to work, the > on-chip IOMMU parent device could implement a separate > .reset_map() operation callback to restore 1:1 DMA mapping > without having to resort to the .reset() callback, the > latter of which is mainly used to reset virtio device state. > This new .reset_map() callback will be invoked only before > the vhost-vdpa driver is to be removed and detached from > the vdpa bus, such that other vdpa bus drivers, e.g. > virtio-vdpa, can start with 1:1 DMA mapping when they > are attached. For the context, those on-chip IOMMU parent > devices, create the 1:1 DMA mapping at vdpa device creation, > and they would implicitly destroy the 1:1 mapping when > the first .set_map or .dma_map callback is invoked. > > This patchset is rebased on top of the latest vhost tree. > > [1] Reducing vdpa migration downtime because of memory pin / maps > https://www.mail-archive.com/qemu-devel@xxxxxxxxxx/msg953755.html > > --- > v4: > - Rework compatibility using new .compat_reset driver op I still think having a set_backend_feature() or reset_map(clean=true) might be better. As it tries hard to not introduce new stuff on the bus. But we can listen to others for sure. Thanks _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
