[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH 0/3] vhost-user reconnect
From: |
Yury Kotov |
Subject: |
Re: [Qemu-devel] [PATCH 0/3] vhost-user reconnect |
Date: |
Mon, 20 Aug 2018 15:51:47 +0300 |
16.08.2018, 18:36, "Marc-André Lureau" <address@hidden>:
> On Thu, Aug 16, 2018 at 5:32 PM, Yury Kotov <address@hidden> wrote:
>> 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.
>
> Can you write a test case in vhost-user-test.c ? (perhaps under
> QTEST_VHOST_USER_FIXME scope...)
>
This is a great idea and we were definitely going to do that during coming
couple of weeks. We thought that we could make a follow up commit with
necessary tests added a bit later though, since currently we need to figure out
the state of vhost-user tests in general, before we can try to add any new
stuff, and that will take some time. So far we have stress-tested these fixes
manually.
Do you suggest we wait with this series as well until we have all tests ready?
Or do we proceed now and make a follow up series with vhost user tests later
like we suggested?
>> 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