在 2022/1/31 下午5:15, Eugenio Perez Martin 写道:
On Fri, Jan 28, 2022 at 7:02 AM Jason Wang <jasowang@xxxxxxxxxx> 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.
A simple single TCP_STREAM netperf test should be sufficient to give
some basic understanding about the performance impact.
Thanks
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-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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