Re: [dpdk-dev] [PATCH] vhost: fix mem share between VM and host

[Thomas Monjalon <thomas.monjalon@6wind.com>]

2016-04-11 01:28, Zhe Tao:
> The reason cause this problem is that in QEMU, when assign the
> memory-backend-file without share option, will cause QEMU mmap the mem file
> without using the MAP_SHARED flag, so the page cache for that file will not
> shared between other processes, all the upated to the mapping area in the VM
> will not carry through to the vhost-user process.
> 
> According to kernel implementation, data for the new hugetlbfs file will be
> all zero, so check the first RX virtqueue descriptor next field to see
> whether the mem is shared or not, if the mem is shared, the next field should
> not equal to zero, otherwise this mem is not shared between VM and host.

I failed to understand.
Please try to do some short sentences and start by explaining what is the
bug you see. Then you can start explain the root cause and how it can be
fixed (using some short sentences).

I also think it is too late to integrate such code change in 16.04
(even if I don't understand how important it is).