[dpdk-dev] vhost-user technical isssues

Linhaifeng haifeng.lin at huawei.com
Thu Nov 13 07:12:36 CET 2014

On 2014/11/12 5:37, Xie, Huawei wrote:
> Hi Tetsuya:
> There are two major technical issues in my mind for vhost-user implementation.
> 1) memory region map
> Vhost-user passes us file fd and offset for each memory region. Unfortunately the mmap offset is "very" wrong. I discovered this issue long time ago, and also found
> that I couldn't mmap the huge page file even with correct offset(need double check).
> Just now I find that people reported this issue on Nov 3.
> [Qemu-devel] [PULL 27/29] vhost-user: fix mmap offset calculation
> Anyway, I turned to the same idea used in our DPDK vhost-cuse: only use the fd for region(0) to map the  whole file.
> I think we should use this way temporarily to support qemu-2.1 as it has that bug.

this bug is not in dpdk's vhost-user just for qemu's vhost-user backend
> 2) what message is the indicator for vhost start/release?
> Previously  for vhost-cuse, it has SET_BACKEND message.
> What we should do for vhost-user?
> SET_VRING_KICK for start?
> What about for release?
> Unlike the kernel virtio, the DPDK virtio in guest could be restarted. 
> Thoughts?
> -huawei


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