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[Qemu-devel] [PATCH 0/3] vhost-user reconnect
From: |
Yury Kotov |
Subject: |
[Qemu-devel] [PATCH 0/3] vhost-user reconnect |
Date: |
Thu, 16 Aug 2018 18:32:40 +0300 |
We are using QEMU (2.12.0) with SPDK (18.04.1) over vhost-user to emulate block
devices. One of our cases it to restart SPDK without restarting VM (in case
of some updates or smth like it). We tried to use the 'reconnect' option for
the '-chardev' device:
-object memory-backend-file,id=mem0,size=1G,mem-path=/dev/hugepages,share=on \
-numa node,memdev=mem0 \
-chardev socket,id=spdk_vhost_blk1,path=/var/tmp/vhost.1,reconnect=10 \
-device vhost-user-blk-pci,chardev=spdk_vhost_blk1,num-queues=4
After this, vhost-user-blk initialization fails with an error below:
qemu-system-x86_64: -device ...: Failed to set msg fds.
qemu-system-x86_64: -device ...: vhost-user-blk: vhost initialization failed:
Operation not permitted
We got the same error with the latest QEMU (c542a9f9794ec8e0bc3f).
We made some investigations and found out that there are several issues:
1. Reconnect option postpones the first connection till machine init done event.
But we need this connection during vhost blk device initialization which
happens before the machine init done handling.
2. If the connection is forced, then the reconnection will be successful
after SPDK restart. The problem is that virtual queue will not start.
The reason for it is that virtual queue initialization commands
should be resent:
* VHOST_USER_SET_FEATURES
* VHOST_USER_SET_MEM_TABLE
* VHOST_USER_SET_VRING_NUM
* VHOST_USER_SET_VRING_BASE
* VHOST_USER_SET_VRING_ADDR
* VHOST_USER_SET_VRING_KICK
* VHOST_USER_SET_VRING_CALL
The patch set resolves both of these issues.
Test case:
1. Start fio process (inside VM):
fio --name test --ioengine=libaio --iodepth=64 --bs=4096 \
--rw=randrw --direct=1 --sync=1 --verify=md5 \
--size=64M --filename=/dev/vda --loops=100
2. Restart SPDK many times.
We are expecting that during SPDK restart fio will pause and fio should
continue to work after restart completion.
3. fio process completed successfully without any error.
Yury Kotov (3):
chardev: prevent extra connection attempt in tcp_chr_machine_done_hook
vhost: refactor vhost_dev_start and vhost_virtqueue_start
vhost-user: add reconnect support for vhost-user
chardev/char-socket.c | 5 +-
hw/virtio/vhost-user.c | 65 ++++++++++++--
hw/virtio/vhost.c | 223 +++++++++++++++++++++++++++++++---------------
include/hw/virtio/vhost.h | 2 +
4 files changed, 215 insertions(+), 80 deletions(-)
--
2.7.4