? 2021/10/1 ??3:05, Eugenio P?rez ??:> This series enable shadow virtqueue (SVQ) for vhost-vdpa devices. This
> is intended as a new method of tracking the memory the devices touch
> during a migration process: Instead of relay on vhost device's dirty
> logging capability, SVQ intercepts the VQ dataplane forwarding the
> descriptors between VM and device. This way qemu is the effective
> writer of guests memory, like in qemu's virtio device operation.
>
> When SVQ is enabled qemu offers a new vring to the device to read
> and write into, and also intercepts kicks and calls between the device
> and the guest. Used buffers relay would cause dirty memory being
> tracked, but at this RFC SVQ is not enabled on migration automatically.
>
> It is based on the ideas of DPDK SW assisted LM, in the series of
> DPDK's https://patchwork.dpdk.org/cover/48370/ . However, these does
> not map the shadow vq in guest's VA, but in qemu's.
>
> For qemu to use shadow virtqueues the guest virtio driver must not use
> features like event_idx or indirect descriptors. These limitations will
> be addressed in later series, but they are left out for simplicity at
> the moment.
>
> SVQ needs to be enabled with QMP command:
>
> { "execute": "x-vhost-enable-shadow-vq",
> "arguments": { "name": "dev0",
"enable": true } }
>
> This series includes some patches to delete in the final version that
> helps with its testing. The first two of the series freely implements
> the feature to stop the device and be able to retrieve its status. It's
> intended to be used with vp_vpda driver in a nested environment. This
> driver also need modifications to forward the new status bit.
>
> Patches 2-8 prepares the SVQ and QMP command to support guest to host
> notifications forwarding. If the SVQ is enabled with these ones
> applied and the device supports it, that part can be tested in
> isolation (for example, with networking), hopping through SVQ.
>
> Same thing is true with patches 9-13, but with device to guest
> notifications.
>
> The rest of the patches implements the actual buffer forwarding.
>
> Comments are welcome.
Hi Eugenio:
It would be helpful to have a public git repo for us to ease the review.
Thanks
>
> TODO:
> * Event, indirect, packed, and others features of virtio - Waiting for
> confirmation of the big picture.
> * Use already available iova tree to track mappings.
> * To sepparate buffers forwarding in its own AIO context, so we can
> throw more threads to that task and we don't need to stop the main
> event loop.
> * unmap iommu memory. Now the tree can only grow from SVQ enable, but
> it should be fine as long as not a lot of memory is added to the
> guest.
> * Rebase on top of latest qemu (and, hopefully, on top of multiqueue
> vdpa).
> * Some assertions need to be appropiate error handling paths.
> * Proper documentation.
>
> Changes from v3 RFC:
> * Move everything to vhost-vdpa backend. A big change, this allowed
> some cleanup but more code has been added in other places.
> * More use of glib utilities, especially to manage memory.
> v3 link:
> https://lists.nongnu.org/archive/html/qemu-devel/2021-05/msg06032.html
>
> Changes from v2 RFC:
> * Adding vhost-vdpa devices support
> * Fixed some memory leaks pointed by different comments
> v2 link:
> https://lists.nongnu.org/archive/html/qemu-devel/2021-03/msg05600.html
>
> Changes from v1 RFC:
> * Use QMP instead of migration to start SVQ mode.
> * Only accepting IOMMU devices, closer behavior with target devices
> (vDPA)
> * Fix invalid masking/unmasking of vhost call fd.
> * Use of proper methods for synchronization.
> * No need to modify VirtIO device code, all of the changes are
> contained in vhost code.
> * Delete superfluous code.
> * An intermediate RFC was sent with only the notifications forwarding
> changes. It can be seen in
> https://patchew.org/QEMU/20210129205415.876290-1-eperezma at
redhat.com/
> v1 link:
> https://lists.gnu.org/archive/html/qemu-devel/2020-11/msg05372.html
>
> Eugenio P?rez (20):
> virtio: Add VIRTIO_F_QUEUE_STATE
> virtio-net: Honor VIRTIO_CONFIG_S_DEVICE_STOPPED
> virtio: Add virtio_queue_is_host_notifier_enabled
> vhost: Make vhost_virtqueue_{start,stop} public
> vhost: Add x-vhost-enable-shadow-vq qmp
> vhost: Add VhostShadowVirtqueue
> vdpa: Register vdpa devices in a list
> vhost: Route guest->host notification through shadow virtqueue
> Add vhost_svq_get_svq_call_notifier
> Add vhost_svq_set_guest_call_notifier
> vdpa: Save call_fd in vhost-vdpa
> vhost-vdpa: Take into account SVQ in vhost_vdpa_set_vring_call
> vhost: Route host->guest notification through shadow virtqueue
> virtio: Add vhost_shadow_vq_get_vring_addr
> vdpa: Save host and guest features
> vhost: Add vhost_svq_valid_device_features to shadow vq
> vhost: Shadow virtqueue buffers forwarding
> vhost: Add VhostIOVATree
> vhost: Use a tree to store memory mappings
> vdpa: Add custom IOTLB translations to SVQ
>
> Eugenio P?rez (20):
> virtio: Add VIRTIO_F_QUEUE_STATE
> virtio-net: Honor VIRTIO_CONFIG_S_DEVICE_STOPPED
> virtio: Add virtio_queue_is_host_notifier_enabled
> vhost: Make vhost_virtqueue_{start,stop} public
> vhost: Add x-vhost-enable-shadow-vq qmp
> vhost: Add VhostShadowVirtqueue
> vdpa: Register vdpa devices in a list
> vhost: Route guest->host notification through shadow virtqueue
> vdpa: Save call_fd in vhost-vdpa
> vhost-vdpa: Take into account SVQ in vhost_vdpa_set_vring_call
> vhost: Route host->guest notification through shadow virtqueue
> virtio: Add vhost_shadow_vq_get_vring_addr
> vdpa: Save host and guest features
> vhost: Add vhost_svq_valid_device_features to shadow vq
> vhost: Shadow virtqueue buffers forwarding
> vhost: Check for device VRING_USED_F_NO_NOTIFY at shadow virtqueue
> kick
> vhost: Use VRING_AVAIL_F_NO_INTERRUPT at device call on shadow
> virtqueue
> vhost: Add VhostIOVATree
> vhost: Use a tree to store memory mappings
> vdpa: Add custom IOTLB translations to SVQ
>
> qapi/net.json | 23 +
> hw/virtio/vhost-iova-tree.h | 40 ++
> hw/virtio/vhost-shadow-virtqueue.h | 37 ++
> hw/virtio/virtio-pci.h | 1 +
> include/hw/virtio/vhost-vdpa.h | 13 +
> include/hw/virtio/vhost.h | 4 +
> include/hw/virtio/virtio.h | 5 +-
> .../standard-headers/linux/virtio_config.h | 5 +
> include/standard-headers/linux/virtio_pci.h | 2 +
> hw/net/virtio-net.c | 6 +-
> hw/virtio/vhost-iova-tree.c | 230 +++++++
> hw/virtio/vhost-shadow-virtqueue.c | 619 ++++++++++++++++++
> hw/virtio/vhost-vdpa.c | 412 +++++++++++-
> hw/virtio/vhost.c | 12 +-
> hw/virtio/virtio-pci.c | 16 +-
> hw/virtio/virtio.c | 5 +
> hw/virtio/meson.build | 2 +-
> hw/virtio/trace-events | 1 +
> 18 files changed, 1413 insertions(+), 20 deletions(-)
> create mode 100644 hw/virtio/vhost-iova-tree.h
> create mode 100644 hw/virtio/vhost-shadow-virtqueue.h
> create mode 100644 hw/virtio/vhost-iova-tree.c
> create mode 100644 hw/virtio/vhost-shadow-virtqueue.c
>