On Fri, Sep 11, 2015 at 10:53 AM, Stefan Hajnoczi <stefanha@xxxxxxxxx> wrote: > On Fri, Sep 11, 2015 at 6:21 PM, Ming Lin <mlin@xxxxxxxxxx> wrote: >> On Fri, 2015-09-11 at 08:48 +0100, Stefan Hajnoczi wrote: >>> On Thu, Sep 10, 2015 at 6:28 PM, Ming Lin <mlin@xxxxxxxxxx> wrote: >>> > On Thu, 2015-09-10 at 15:38 +0100, Stefan Hajnoczi wrote: >>> >> On Thu, Sep 10, 2015 at 6:48 AM, Ming Lin <mlin@xxxxxxxxxx> wrote: >>> >> > These 2 patches added virtio-nvme to kernel and qemu, >>> >> > basically modified from virtio-blk and nvme code. >>> >> > >>> >> > As title said, request for your comments. >>> >> > >>> >> > Play it in Qemu with: >>> >> > -drive file=disk.img,format=raw,if=none,id=D22 \ >>> >> > -device virtio-nvme-pci,drive=D22,serial=1234,num_queues=4 >>> >> > >>> >> > The goal is to have a full NVMe stack from VM guest(virtio-nvme) >>> >> > to host(vhost_nvme) to LIO NVMe-over-fabrics target. >>> >> >>> >> Why is a virtio-nvme guest device needed? I guess there must either >>> >> be NVMe-only features that you want to pass through, or you think the >>> >> performance will be significantly better than virtio-blk/virtio-scsi? >>> > >>> > It simply passes through NVMe commands. >>> >>> I understand that. My question is why the guest needs to send NVMe commands? >>> >>> If the virtio_nvme.ko guest driver only sends read/write/flush then >>> there's no advantage over virtio-blk. >>> >>> There must be something you are trying to achieve which is not >>> possible with virtio-blk or virtio-scsi. What is that? >> >> I actually learned from your virtio-scsi work. >> http://www.linux-kvm.org/images/f/f5/2011-forum-virtio-scsi.pdf >> >> Then I thought a full NVMe stack from guest to host to target seems >> reasonable. >> >> Trying to achieve similar things as virtio-scsi, but all NVMe protocol. >> >> - Effective NVMe passthrough >> - Multiple target choices: QEMU, LIO-NVMe(vhost_nvme) >> - Almost unlimited scalability. Thousands of namespaces per PCI device >> - True NVMe device >> - End-to-end Protection Information >> - .... > > The advantages you mentioned are already available in virtio-scsi, > except for the NVMe command set. > > I don't understand what unique problem virtio-nvme solves yet. If > someone asked me to explain why NVMe-over-virtio makes sense compared > to the existing virtio-blk/virtio-scsi or NVMe SR-IOV options, I > wouldn't know the answer. I'd like to learn that from you or anyone > else on CC. > > Do you have a use case in mind? One use case is for All NVMe storage array. There is no SCSI device at all. Samsung demoed one in flash memory summit 2015. http://www.tomsitpro.com/articles/best-of-flash-memory-summit,1-2806.html > > Stefan _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
