netdev - Re: [PATCH v8 00/10] Introduce VDUSE

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Date:   Tue, 29 Jun 2021 12:12:57 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Yongji Xie <elohimes@...il.com>,
        Liu Xiaodong <xiaodong.liu@...el.com>
Cc:     Xie Yongji <xieyongji@...edance.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>, sgarzare@...hat.com,
        parav@...dia.com, hch@...radead.org,
        christian.brauner@...onical.com, rdunlap@...radead.org,
        willy@...radead.org, viro@...iv.linux.org.uk, axboe@...nel.dk,
        bcrl@...ck.org, corbet@....net, mika.penttila@...tfour.com,
        dan.carpenter@...cle.com, joro@...tes.org,
        gregkh@...uxfoundation.org, kvm@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        iommu@...ts.linux-foundation.org, songmuchun@...edance.com,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v8 00/10] Introduce VDUSE - vDPA Device in Userspace


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.

So we need to think carefully of mmap() vs umem registering.

Thanks