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Subject: Re: Re: [virtio-comment] About adding a new device type virtio-nvme
On Tue, 17 Jan 2023 19:19:59 +0200, Max Gurtovoy wrote: >On 17/01/2023 4:04, äèä wrote: >> On Wed, 11 Jan 2023 10:16:55 -0500, Stefan wrote: >> >> >>>> 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 ? >> >> >> >> >> >> >>> 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. >> >> 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 >> >> >> >>> 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. Yes, VFIO live migration framework is WIP, but I still think vdpa is a friendlier 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. Yes, you're right. Nvme has a built-in advantage over virtio-blk hardware offloading. The reason why I propose Virtio-NVMe is to combine nvme and virtio, so that NVME can adapt to virtio ecosystem based on virtio interface specifications, such as vdpa. -- Leo Hou/houyingle
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