On Tue, Mar 08, 2022 at 03:14:35PM +0800, Jason Wang wrote: > On Tue, Mar 8, 2022 at 3:11 PM Michael S. Tsirkin <m...@redhat.com> wrote: > > > > On Tue, Mar 08, 2022 at 02:03:32PM +0800, Jason Wang wrote: > > > > > > 在 2022/3/7 下午11:33, Eugenio Pérez 写道: > > > > 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 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. > > > > > > > > This effectively means that vDPA device passthrough is intercepted by > > > > qemu. While SVQ should only be enabled at migration time, the switching > > > > from regular mode to SVQ mode is left for a future series. > > > > > > > > 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. > > > > > > > > SVQ needs to be enabled with cmdline: > > > > > > > > -netdev type=vhost-vdpa,vhostdev=vhost-vdpa-0,id=vhost-vdpa0,svq=on > > > > A stable API for an incomplete feature is a problem imho. > > It should be "x-svq".
Well look at patch 15. > > > > > > > > > > > > The first three patches enables notifications forwarding with > > > > assistance of qemu. It's easy to enable only this if the relevant > > > > cmdline part of the last patch is applied on top of these. > > > > > > > > Next four patches implement the actual buffer forwarding. However, > > > > address are not translated from HVA so they will need a host device with > > > > an iommu allowing them to access all of the HVA range. > > > > > > > > The last part of the series uses properly the host iommu, so qemu > > > > creates a new iova address space in the device's range and translates > > > > the buffers in it. Finally, it adds the cmdline parameter. > > > > > > > > Some simple performance tests with netperf were done. They used a nested > > > > guest with vp_vdpa, vhost-kernel at L0 host. Starting with no svq and a > > > > baseline average of ~9009.96Mbps: > > > > Recv Send Send > > > > Socket Socket Message Elapsed > > > > Size Size Size Time Throughput > > > > bytes bytes bytes secs. 10^6bits/sec > > > > 131072 16384 16384 30.01 9061.03 > > > > 131072 16384 16384 30.01 8962.94 > > > > 131072 16384 16384 30.01 9005.92 > > > > > > > > To enable SVQ buffers forwarding reduce throughput to about > > > > Recv Send Send > > > > Socket Socket Message Elapsed > > > > Size Size Size Time Throughput > > > > bytes bytes bytes secs. 10^6bits/sec > > > > 131072 16384 16384 30.01 7689.72 > > > > 131072 16384 16384 30.00 7752.07 > > > > 131072 16384 16384 30.01 7750.30 > > > > > > > > However, many performance improvements were left out of this series for > > > > simplicity, so difference should shrink in the future. > > > > > > > > Comments are welcome. > > > > > > > > > Hi Michael: > > > > > > What do you think of this series? It looks good to me as a start. The > > > feature could only be enabled as a dedicated parameter. If you're ok, I'd > > > try to make it for 7.0. > > > > > > Thanks > > > > Well that's cutting it awfully close, and it's not really useful > > at the current stage, is it? > > This allows vDPA to be migrated when using "x-svq=on". > But anyhow it's > experimental. it's less experimental than incomplete. It seems pretty clearly not the way it will work down the road, we don't want svq involved at all times. > > > > The IOVA trick does not feel complete either. > > I don't get here. We don't use any IOVA trick as DPDK (it reserve IOVA > for shadow vq) did. So we won't suffer from the issues of DPDK. > > Thanks Maybe I misundrstand how this all works. I refer to all the iova_tree_alloc_map things. > > > > > > > > > > > > > TODO on future series: > > > > * Event, indirect, packed, and others features of virtio. > > > > * To support different set of features between the device<->SVQ and the > > > > SVQ<->guest communication. > > > > * Support of device host notifier memory regions. > > > > * 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. > > > > * Support multiqueue virtio-net vdpa. > > > > * Proper documentation. > > > > > > > > Changes from v4: > > > > * Iterate iova->hva tree instead on maintain own tree so we support HVA > > > > overlaps. > > > > * Fix: Errno completion at failure. > > > > * Rename x-svq to svq, so changes to stable does not affect cmdline > > > > parameter. > > > > > > > > Changes from v3: > > > > * Add @unstable feature to NetdevVhostVDPAOptions.x-svq. > > > > * Fix uncomplete mapping (by 1 byte) of memory regions if svq is > > > > enabled. > > > > v3 link: > > > > https://lore.kernel.org/qemu-devel/20220302203012.3476835-1-epere...@redhat.com/ > > > > > > > > Changes from v2: > > > > * Less assertions and more error handling in iova tree code. > > > > * Better documentation, both fixing errors and making @param: format > > > > * Homogeneize SVQ avail_idx_shadow and shadow_used_idx to make shadow a > > > > prefix at both times. > > > > * Fix: Fo not use VirtQueueElement->len field, track separatedly. > > > > * Split vhost_svq_{enable,disable}_notification, so the code looks more > > > > like the kernel driver code. > > > > * Small improvements. > > > > v2 link: > > > > https://lore.kernel.org/all/cajaqywfxhe0c54r_-oiwjzjc0gppke3ex0l8beezxgm1ery...@mail.gmail.com/ > > > > > > > > Changes from v1: > > > > * Feature set at device->SVQ is now the same as SVQ->guest. > > > > * Size of SVQ is not max available device size anymore, but guest's > > > > negotiated. > > > > * Add VHOST_FILE_UNBIND kick and call fd treatment. > > > > * Make SVQ a public struct > > > > * Come back to previous approach to iova-tree > > > > * Some assertions are now fail paths. Some errors are now log_guest. > > > > * Only mask _F_LOG feature at vdpa_set_features svq enable path. > > > > * Refactor some errors and messages. Add missing error unwindings. > > > > * Add memory barrier at _F_NO_NOTIFY set. > > > > * Stop checking for features flags out of transport range. > > > > v1 link: > > > > https://lore.kernel.org/virtualization/7d86c715-6d71-8a27-91f5-8d47b71e3...@redhat.com/ > > > > > > > > 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 (15): > > > > vhost: Add VhostShadowVirtqueue > > > > vhost: Add Shadow VirtQueue kick forwarding capabilities > > > > vhost: Add Shadow VirtQueue call forwarding capabilities > > > > vhost: Add vhost_svq_valid_features to shadow vq > > > > virtio: Add vhost_svq_get_vring_addr > > > > vdpa: adapt vhost_ops callbacks to svq > > > > vhost: Shadow virtqueue buffers forwarding > > > > util: Add iova_tree_alloc_map > > > > util: add iova_tree_find_iova > > > > vhost: Add VhostIOVATree > > > > vdpa: Add custom IOTLB translations to SVQ > > > > vdpa: Adapt vhost_vdpa_get_vring_base to SVQ > > > > vdpa: Never set log_base addr if SVQ is enabled > > > > vdpa: Expose VHOST_F_LOG_ALL on SVQ > > > > vdpa: Add x-svq to NetdevVhostVDPAOptions > > > > > > > > qapi/net.json | 8 +- > > > > hw/virtio/vhost-iova-tree.h | 27 ++ > > > > hw/virtio/vhost-shadow-virtqueue.h | 87 ++++ > > > > include/hw/virtio/vhost-vdpa.h | 8 + > > > > include/qemu/iova-tree.h | 38 +- > > > > hw/virtio/vhost-iova-tree.c | 110 +++++ > > > > hw/virtio/vhost-shadow-virtqueue.c | 637 +++++++++++++++++++++++++++++ > > > > hw/virtio/vhost-vdpa.c | 525 +++++++++++++++++++++++- > > > > net/vhost-vdpa.c | 48 ++- > > > > util/iova-tree.c | 169 ++++++++ > > > > hw/virtio/meson.build | 2 +- > > > > 11 files changed, 1633 insertions(+), 26 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 > > > > > >
