# Re: \[PATCH v8 00/10\] Introduce VDUSE - vDPA Device in Userspace

- From: Jason Wang \<hidden\>
- Date: 2021-06-29 07:34:07 
- List: virtualization
- Page: https://ratatoskr.run/virtualization/2021/06/208903
- Thread: https://ratatoskr.run/kvm/2021/06/207854/t.md

```text

在 2021/6/29 下午2:40, Yongji Xie 写道:
> On Tue, Jun 29, 2021 at 12:13 PM Jason Wang [ref] wrote:
>>
>> 在 2021/6/28 下午6:32, Yongji Xie 写道:
>>>> The large barrier is bounce-buffer mapping: SPDK requires hugepages
>>>> for NVMe over PCIe and RDMA, so take some preallcoated hugepages to
>>>> map as bounce buffer is necessary. Or it's hard to avoid an extra
>>>> memcpy from bounce-buffer to hugepage.
>>>> If you can add an option to map hugepages as bounce-buffer,
>>>> then SPDK could also be a potential user of vduse.
>>>>
>>> I think we can support registering user space memory for bounce-buffer
>>> use like XDP does. But this needs to pin the pages, so I didn't
>>> consider it in this initial version.
>>>
>> Note that userspace should be unaware of the existence of the bounce buffer.
>>
> If so, it might be hard to use umem. Because we can't use umem for
> coherent mapping which needs physical address contiguous space.
>
> Thanks,
> Yongji


We probably can use umem for memory other than the virtqueue (still via mmap()).

Thanks


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