On Wed, 2015-09-16 at 23:10 -0700, Nicholas A. Bellinger wrote:
> Hi Ming & Co,
>
> On Thu, 2015-09-10 at 10:28 -0700, Ming Lin 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.
>
> <SNIP>
>
> > >
> > > At first glance it seems like the virtio_nvme guest driver is just
> > > another block driver like virtio_blk, so I'm not clear why a
> > > virtio-nvme device makes sense.
> >
> > I think the future "LIO NVMe target" only speaks NVMe protocol.
> >
> > Nick(CCed), could you correct me if I'm wrong?
> >
> > For SCSI stack, we have:
> > virtio-scsi(guest)
> > tcm_vhost(or vhost_scsi, host)
> > LIO-scsi-target
> >
> > For NVMe stack, we'll have similar components:
> > virtio-nvme(guest)
> > vhost_nvme(host)
> > LIO-NVMe-target
> >
>
> I think it's more interesting to consider a 'vhost style' driver that
> can be used with unmodified nvme host OS drivers.
>
> Dr. Hannes (CC'ed) had done something like this for megasas a few years
> back using specialized QEMU emulation + eventfd based LIO fabric driver,
> and got it working with Linux + MSFT guests.
>
> Doing something similar for nvme would (potentially) be on par with
> current virtio-scsi+vhost-scsi small-block performance for scsi-mq
> guests, without the extra burden of a new command set specific virtio
> driver.
Trying to understand it.
Is it like below?
.------------------------. MMIO .---------------------------------------.
| Guest |--------> | Qemu |
| Unmodified NVMe driver |<-------- | NVMe device simulation(eventfd based) |
'------------------------' '---------------------------------------'
| ^
write NVMe | | notify command
command | | completion
to eventfd | | to eventfd
v |
.--------------------------------------.
| Host: |
| eventfd based LIO NVMe fabric driver |
'--------------------------------------'
|
| nvme_queue_rq()
v
.--------------------------------------.
| NVMe driver |
'--------------------------------------'
|
|
v
.-------------------------------------.
| NVMe device |
'-------------------------------------'
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