[stgt] VSCSI Target Driver

[FUJITA Tomonori]

On Thu, 27 May 2010 10:57:44 -0300
Erlon Cruz <sombrafam at gmail.com> wrote:

> >>       Im working in a project aimed to port Linux virtio to Power
> >
> > you are talking about drivers/virtio?
> 
> Yes, we want virtio paravirtual drivers (block, net and char) running
> on top of Power LPARs and communicating with the VIO server.
> 
> >> Platform, and also documenting vscsi underling operation. While
> >> reading ibmvstgt.c driver, I found something I cant understand:
> >>       The SCSI command is extracted from this transport frame (SRP)
> >> and then pushed to the user space daemon 'tgtd' which process it,
> >> right?
> >
> > Right.
> 
> Hmm, I got it. One more thing, what happen then with the
> scatter/gatter list stored in the SRP frame? Is it sent to the user
> space too?

No, not necessary. The user space daemon cares about only the sector
and length. The daemon maps the page frames including data to send.

Then the kernel space target driver sends the data to the
initiator. If the initiator wants the data in the scatter/gather way,
the kernel space target driver sends the data in such way.


> If so, how will this information be sent back to the kernel
> once, in the user space?
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