On 2018/12/6 下午9:57, Jason Wang wrote:
On 2018/12/6 下午2:35, elohi...@gmail.com wrote:
From: Xie Yongji <xieyon...@baidu.com>
This patchset is aimed at supporting qemu to reconnect
vhost-user-blk backend after vhost-user-blk backend crash or
restart.
The patch 1 tries to implenment the sync connection for
"reconnect socket".
The patch 2 introduces a new message VHOST_USER_SET_VRING_INFLIGHT
to support offering shared memory to backend to record
its inflight I/O.
The patch 3,4 are the corresponding libvhost-user patches of
patch 2. Make libvhost-user support VHOST_USER_SET_VRING_INFLIGHT.
The patch 5 supports vhost-user-blk to reconnect backend when
connection closed.
The patch 6 tells qemu that we support reconnecting now.
To use it, we could start qemu with:
qemu-system-x86_64 \
-chardev
socket,id=char0,path=/path/vhost.socket,reconnect=1,wait \
-device vhost-user-blk-pci,chardev=char0 \
and start vhost-user-blk backend with:
vhost-user-blk -b /path/file -s /path/vhost.socket
Then we can restart vhost-user-blk at any time during VM running.
I wonder whether or not it's better to handle this at the level of
virtio protocol itself instead of vhost-user level. E.g expose
last_avail_idx to driver might be sufficient?
Another possible issue is, looks like you need to deal with different
kinds of ring layouts e.g packed virtqueues.
Thanks
Cc Maxime who wrote vhost-user reconnecting for more thoughts.
Thanks
