Re: [Qemu-devel] [PATCH 0/2] add "nopin" option in the memory-backend-file

[Xiao Guangrong]

On 10/16/2017 04:56 PM, Yang Zhong wrote:
> Qemu does not need pin NVDIMM memory for VFIO device during VFIO
> hotplug, what's more, if there is no NVDIMM hw in the test machine,
> the VFIO hotplug operation will need at least 10 minutes to pin RAM
> as the NVDIMM, this time is not accepted. So we add "nopin=on" option
> in the memory-backed-file, which can avoid to pin RAM memory for NVDIMM.

No.

memory-backed-file does not dedicate for nvdimm only, it can be mapped
as normal memory as well. Rather more, this is no way to stop guest to
use it as DMA.