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

[Max Gurtovoy <mgurtovoy@nvidia.com>]

On 17/01/2023 4:04, 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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> > 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.
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> > 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
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> > 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?
>
>
> virtio-nvmeÂadvantages :
> 1)  live migration

This is WIP and will use VFIO live migration framework.

> 2)  support remote storage

There are solutions today that can use remote storage as an NVMe 
Namespace. For example, DPU based NVMe device such as NVIDIA'S NVMe SNAP 
device.

> Leo Hou/äèä