Re: [virtio-comment] About adding a new device type virtio-nvme

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Wed, Jan 11, 2023 at 11:21:35AM +0800, 侯英乐 wrote:
> As we know, nvme has more features than virtio-blk. For example, with the development of virtualization IO offloading to hardware, virtio-blk and NVME-OF offloading to hardware are developing rapidly.  So if virtio and nvme are combined into Virtio-NvMe, Is it necessary to add a device type Virtio-NvMe ? 

Hi,
In theory, yes, virtio-nvme can be done. The question is why do it?

NVMe already provides a PCI hardware spec for software and hardware
implementations to follow. An NVMe PCI device can be exposed to the
guest and modern operating systems recognize it without requiring new
drivers.

The value of VIRTIO here is probably in the deep integration into the
virtualization stack with vDPA, vhost, etc. A virtio-nvme device can use
all these things whereas a PCI device needs to do everything from
scratch.

Let's not forget that virtio-blk is widely used and new commands are
being added as needed. Which NVMe features are you missing in
virtio-blk?

I guess this is why virtio-nvme hasn't been done before: people who want
NVMe can already do NVMe PCI, people who want VIRTIO can use virtio-blk,
and so there hasn't been a great need to combine VIRTIO and NVMe yet.
What advantages do you see in having virtio-nvme?

Stefan

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