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

[Stefan Hajnoczi <stefanha@redhat.com>]

On Tue, Jan 17, 2023 at 10:04:07AM +0800, äèä wrote:
> On Wed, 11 Jan 2023 10:16:55 -0500, Stefan wrote:
> 
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> >>On Wed, Jan 11, 2023 at 11:21:35AM +0800, äèä 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 ?
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> Â
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> >Hi,
> >In theory, yes, virtio-nvme can be done. The question is why do it?
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> >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.
> 
> 
> The NVME technology and ecosystem are complete. However, in virtualization scenarios, NVME devices can only use PCIe pass-through . When NVME and virtio combine to connect to the vDPA ecosystem, live migration is supported.
> 
> 
> >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?
> 
> With the introduction of the concept of DPU, a large number of vendors are offloading virtual devices to hardware. The back-end of Virtio-blk does not support remote storage. Therefore, Virtio-Nvme-of can well combine the advantages of remote storage and virtio live migration

virtio-blk is just a storage interface, whether that storage is local or
remote is up to the device implementation. The block device could be
located on Ceph, NFS, etc.

Each virtio-blk device is a single block device. There is no
standardized management protocol in virtio-blk for connecting to remote
block devices. I'm aware of hardware virtio-blk devices that connect to
remote storage. Configuration is performed through an out-of-band
management interface.

Maybe when you say virtio-blk doesn't support remote storage this is
what you mean?

Stefan

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