在 2022/1/22 上午4:27, Eugenio Pérez 写道:
This series enables 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 emulated virtio device operation. When SVQ is enabled qemu offers a new virtual address space to the device to read and write into, and it maps new vrings and the guest memory in it. SVQ 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. Thanks of being a buffers relay system, SVQ can be used also to communicate devices and drivers with different capabilities, like devices that only support packed vring and not split and old guests with no driver packed support. 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. This version of SVQ is limited in the amount of features it can use with guest and device, because this series is already very big otherwise. Features like indirect or event_idx will be addressed in future series. SVQ needs to be enabled with cmdline parameter x-svq, like: -netdev type=vhost-vdpa,vhostdev=/dev/vhost-vdpa-0,id=vhost-vdpa0,x-svq=true In this version it cannot be enabled or disabled in runtime. Further series will remove this limitation and will enable it only for migration time. Some patches are intentionally very small to ease review, but they can be squashed if preferred. Patches 1-10 prepares the SVQ and QEMU to support both guest to device and device to guest notifications forwarding, with the extra qemu hop. That part can be tested in isolation if cmdline change is reproduced. Patches from 11 to 18 implement the actual buffer forwarding, but with no IOMMU support. It requires a vdpa device capable of addressing all qemu vaddr. Patches 19 to 23 adds the iommu support, so the device with address range limitations can access SVQ through this new virtual address space created. The rest of the series add the last pieces needed for migration. Comments are welcome.
I wonder the performance impact. So performance numbers are more than welcomed.
Thanks
TODO: * Event, indirect, packed, and other features of virtio. * To separate 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. * Support virtio-net control vq. * Proper documentation. Changes from v5 RFC: * Remove dynamic enablement of SVQ, making less dependent of the device. * Enable live migration if SVQ is enabled. * Fix SVQ when driver reset. * Comments addressed, specially in the iova area. * Rebase on latest master, adding multiqueue support (but no networking control vq processing). v5 link: https://lists.gnu.org/archive/html/qemu-devel/2021-10/msg07250.html Changes from v4 RFC: * Support of allocating / freeing iova ranges in IOVA tree. Extending already present iova-tree for that. * Proper validation of guest features. Now SVQ can negotiate a different set of features with the device when enabled. * Support of host notifiers memory regions * Handling of SVQ full queue in case guest's descriptors span to different memory regions (qemu's VA chunks). * Flush pending used buffers at end of SVQ operation. * QMP command now looks by NetClientState name. Other devices will need to implement it's way to enable vdpa. * Rename QMP command to set, so it looks more like a way of working * Better use of qemu error system * Make a few assertions proper error-handling paths. * Add more documentation * Less coupling of virtio / vhost, that could cause friction on changes * Addressed many other small comments and small fixes. 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@xxxxxxxxxx/ v1 link: https://lists.gnu.org/archive/html/qemu-devel/2020-11/msg05372.html Eugenio Pérez (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 Pérez (31): vdpa: Reorder virtio/vhost-vdpa.c functions vhost: Add VhostShadowVirtqueue vdpa: Add vhost_svq_get_dev_kick_notifier vdpa: Add vhost_svq_set_svq_kick_fd vhost: Add Shadow VirtQueue kick forwarding capabilities vhost: Route guest->host notification through shadow virtqueue vhost: dd vhost_svq_get_svq_call_notifier vhost: Add vhost_svq_set_guest_call_notifier vhost-vdpa: Take into account SVQ in vhost_vdpa_set_vring_call vhost: Route host->guest notification through shadow virtqueue vhost: Add vhost_svq_valid_device_features to shadow vq vhost: Add vhost_svq_valid_guest_features to shadow vq vhost: Add vhost_svq_ack_guest_features to shadow vq virtio: Add vhost_shadow_vq_get_vring_addr vdpa: Add vhost_svq_get_num vhost: pass queue index to vhost_vq_get_addr vdpa: adapt vhost_ops callbacks to svq vhost: Shadow virtqueue buffers forwarding utils: Add internal DMAMap to iova-tree util: Store DMA entries in a list util: Add iova_tree_alloc vhost: Add VhostIOVATree vdpa: Add custom IOTLB translations to SVQ vhost: Add vhost_svq_get_last_used_idx vdpa: Adapt vhost_vdpa_get_vring_base to SVQ vdpa: Clear VHOST_VRING_F_LOG at vhost_vdpa_set_vring_addr in SVQ vdpa: Never set log_base addr if SVQ is enabled vdpa: Expose VHOST_F_LOG_ALL on SVQ vdpa: Make ncs autofree vdpa: Move vhost_vdpa_get_iova_range to net/vhost-vdpa.c vdpa: Add x-svq to NetdevVhostVDPAOptions qapi/net.json | 5 +- hw/virtio/vhost-iova-tree.h | 27 + hw/virtio/vhost-shadow-virtqueue.h | 46 ++ include/hw/virtio/vhost-vdpa.h | 7 + include/qemu/iova-tree.h | 17 + hw/virtio/vhost-iova-tree.c | 157 ++++++ hw/virtio/vhost-shadow-virtqueue.c | 761 +++++++++++++++++++++++++++++ hw/virtio/vhost-vdpa.c | 740 ++++++++++++++++++++++++---- hw/virtio/vhost.c | 6 +- net/vhost-vdpa.c | 58 ++- util/iova-tree.c | 161 +++++- hw/virtio/meson.build | 2 +- 12 files changed, 1852 insertions(+), 135 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
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