On Tue, Dec 6, 2022 at 1:04 AM Eugenio Pérez <epere...@redhat.com> wrote: > > The state of the descriptors (avail or used) may not be recoverable just > looking at the guest memory. Out of order used descriptor may override > previous avail ones in the descriptor table or avail vring. > > Currently we're not migrating this status in net devices because virtio-net, > vhost-kernel etc use the descriptors in order,
Note that this might not be the truth (when zerocopy is enabled). > so the information always > recoverable from guest's memory. However, vDPA devices may use them out of > order, and other kind of devices like block need this support. > > Shadow virtqueue is able to track these and resend them at the destination. As discussed, there's a bootstrap issue here: When SVQ needs to be enabled on demand, do we still need another way to get inflight ones without the help of SVQ? Thanks > Add them to the virtio-net migration description so they are not lose in the > process. > > This is a very early RFC just to validate the first draft so expect leftovers. > To fetch and request the descriptors from a device without SVQ need to be > implemented on top. Some other notable pending items are: > * Do not send the descriptors actually recoverable from the guest memory. > * Properly version the migrate data. > * Properly abstract the descriptors access from virtio-net to SVQ. > * Do not use VirtQueueElementOld but migrate directly VirtQueueElement. > * Replace lots of assertions with runtime conditionals. > * Other TODOs in the patch message or code changes. > > Thanks. > > Eugenio Pérez (13): > vhost: add available descriptor list in SVQ > vhost: iterate only available descriptors at SVQ stop > vhost: merge avail list and next avail descriptors detach > vhost: add vhost_svq_save_inflight > virtio: Specify uint32_t as VirtQueueElementOld members type > virtio: refactor qemu_get_virtqueue_element > virtio: refactor qemu_put_virtqueue_element > virtio: expose VirtQueueElementOld > virtio: add vmstate_virtqueue_element_old > virtio-net: Migrate vhost inflight descriptors > virtio-net: save inflight descriptors at vhost shutdown > vhost: expose vhost_svq_add_element > vdpa: Recover inflight descriptors > > hw/virtio/vhost-shadow-virtqueue.h | 9 ++ > include/hw/virtio/virtio-net.h | 2 + > include/hw/virtio/virtio.h | 32 ++++++ > include/migration/vmstate.h | 22 ++++ > hw/net/vhost_net.c | 56 ++++++++++ > hw/net/virtio-net.c | 129 +++++++++++++++++++++++ > hw/virtio/vhost-shadow-virtqueue.c | 52 +++++++-- > hw/virtio/vhost-vdpa.c | 11 -- > hw/virtio/virtio.c | 162 ++++++++++++++++++----------- > 9 files changed, 392 insertions(+), 83 deletions(-) > > -- > 2.31.1 > >
