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Subject: Re: Re: [virtio-comment] About adding a new device type virtio-nvme
On Sun, 5 Feb 2023 07:33:17 -0500, Michael S. Tsirkin wrote: >On Wed, Jan 18, 2023 at 10:49:23AM +0800, äèä wrote: >> On Tue, 17 Jan 2023 11:01:37 -0500, Stefan wrote: >> >> >On Tue, Jan 17, 2023 at 10:04:07AM +0800, 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 >> > >> >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? >> >> >> >> Yes, virtio-blk devices offlaod to hardware, For example, DPU and SmartNIC. >> So, compare virtio-nvme with virtio-blk and NVME. >> >> >> >> >> >> Stefan >> > >Let's circle back a bit. You asked: >So if virtio and nvme are combined into Virtio-NvMe, Is it >necessary to add a device type Virtio-NvMe ? >And the answer seems to be: >not without much more in the way of motivation.  Yes, the conclusion is this. Thanks! ---- Leo  Â
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