Re: [Qemu-devel] If Qemu support NVMe over Fabrics ?y

[Stefan Hajnoczi]

On Fri, Jan 11, 2019 at 11:48:52AM +0100, Paolo Bonzini wrote:
> On 11/01/19 06:46, Yang Zhong wrote:
> > On Thu, Jan 10, 2019 at 10:36:37AM +0000, Stefan Hajnoczi wrote:
> >> On Thu, Jan 10, 2019 at 04:37:53PM +0800, Yang Zhong wrote:
> >>> Do you know if Qemu support NVMe over Fabrics(NVMe-oF)?
> >>> https://nvmexpress.org/wp-content/uploads/NVMe_Over_Fabrics.pdf
> >>>
> >>> The Qemu has enabled RDMA in last year, and i am not sure if Qemu 
> >>> should support NVME-oF. If Qemu support it, would you please share
> >>> me the qemu related command or guides? thanks a lot!
> >>
> >> QEMU supports many different storage configurations.  Can you be more
> >> specific?
> >>
> >> For example, if your host has NVMe-oF set up then you can give the NVMe
> >> block devices to QEMU just like any other host block device (-drive
> >> file=/dev/sdc,...).
> >>
> >> But maybe you are thinking about other configurations, like exposing
> >> NVMe-oF to the guest?
> >>
> >   Thanks Stefan's comments. We only want Qemu as NVMe-oF initiator to
> >   access remote target's resource.
> > 
> >   I checked the block/nvme.c and hw/block/nvme.c code, which seems do
> >   not support NVMe-oF . If i am wrong please correct me.
> > 
> >   If Qemu support NVMe-oF initiator, please share me how to use it. 
> >   If Qemu does not support it, please tell me if community has plan 
> >   to implement it. thanks a lot!
> 
> QEMU's native NVMe driver only supports NVMe over PCI, but it should be
> possible to extract common code if you want to add a native NVMe over
> RDMA driver to QEMU.  There are currently no plans to add such a driver,
> but it would certainly be a welcome addition.

Before investing time in doing that, what is the goal?

Is this for test and bring-up of NVMe-oF?  Or why does the guest need to
know that the storage is NVMe-oF?

As I mentioned before, if your host supports NVMe-oF you can simply give
the block device to QEMU and let the guest access it via virtio-blk,
virtio-scsi, NVMe, etc.

Stefan

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