On Fri, Jan 28, 2022 at 7:02 AM Jason Wang <jasow...@redhat.com> wrote: > > > 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. >
Sure, I'll do it for the next revision. Since this one brings a decent amount of changes, I chose to collect the feedback first. Thanks! > 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-epere...@redhat.com/ > > 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 > > >
