Date:	Fri, 16 Aug 2013 17:08:13 +0000
From:	"Waskiewicz Jr, Peter P" <peter.p.waskiewicz.jr@...el.com>
To:	"Dutt, Sudeep" <sudeep.dutt@...el.com>
CC:	Pavel Machek <pavel@....cz>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Arnd Bergmann <arnd@...db.de>,
	Rusty Russell <rusty@...tcorp.com.au>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Rob Landley <rob@...dley.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"virtualization@...ts.linux-foundation.org" 
	<virtualization@...ts.linux-foundation.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"Rao, Nikhil" <nikhil.rao@...el.com>,
	"Dixit, Ashutosh" <ashutosh.dixit@...el.com>,
	"Yokoyama, Caz" <caz.yokoyama@...el.com>,
	"Chandramouli, Dasaratharaman" 
	<dasaratharaman.chandramouli@...el.com>,
	"Kharche, Harshavardhan R" <harshavardhan.r.kharche@...el.com>,
	"Dong, Eddie" <eddie.dong@...el.com>
Subject: Re: [PATCH 0/5] Enable Drivers for Intel MIC X100 Coprocessors.

On Fri, 2013-08-16 at 09:59 -0700, Sudeep Dutt wrote:
> On Thu, 2013-08-15 at 12:14 +0200, Pavel Machek wrote:
> > Hi!
> > 
> 
> Hi!
> 
> > > > > Since it is a PCIe card, it does not have the ability to host hardware
> > > > > devices for networking, storage and console. We provide these devices
> > > > > on X100 coprocessors thus enabling a self-bootable equivalent environment
> > > > > for applications. A key benefit of our solution is that it leverages
> > > > > the standard virtio framework for network, disk and console devices,
> > > > > though in our case the virtio framework is used across a PCIe bus.
> > > > 
> > > > Interesting...
> > > > 
> > > > >  Documentation/mic/mic_overview.txt   |   48 +
> > > > >  Documentation/mic/mpssd/.gitignore   |    1 +
> > > > >  Documentation/mic/mpssd/Makefile     |   20 +
> > > > >  Documentation/mic/mpssd/micctrl      |  157 +++
> > > > >  Documentation/mic/mpssd/mpss         |  246 +++++
> > > > >  Documentation/mic/mpssd/mpssd.c      | 1732 ++++++++++++++++++++++++++++++++++
> > > > >  Documentation/mic/mpssd/mpssd.h      |  105 +++
> > > > >  Documentation/mic/mpssd/sysfs.c      |  108 +++
> > > > >  drivers/misc/Kconfig                 |    1 +
> > > > >  drivers/misc/Makefile                |    1 +
> > > > >  drivers/misc/mic/Kconfig             |   56 ++
> > > > >  drivers/misc/mic/Makefile            |    6 +
> > > > >  drivers/misc/mic/card/Makefile       |   11 +
> > > > >  drivers/misc/mic/card/mic_common.h   |   43 +
> > > > >  drivers/misc/mic/card/mic_debugfs.c  |  139 +++
> > > > >  drivers/misc/mic/card/mic_debugfs.h  |   40 +
> > > > >  drivers/misc/mic/card/mic_device.c   |  311 ++++++
> > > > >  drivers/misc/mic/card/mic_device.h   |  106 +++
> > > > >  drivers/misc/mic/card/mic_virtio.c   |  643 +++++++++++++
> > > > >  drivers/misc/mic/card/mic_virtio.h   |   79 ++
> > > > >  drivers/misc/mic/card/mic_x100.c     |  253 +++++
> > > > >  drivers/misc/mic/card/mic_x100.h     |   53 ++
> > > > >  drivers/misc/mic/common/mic_device.h |   85 ++
> > > > >  drivers/misc/mic/host/Makefile       |   13 +
> > > > >  drivers/misc/mic/host/mic_boot.c     |  181 ++++
> > > > 
> > > > So... there are basically separate computers running on PCIe card
> > > > plugged into host computer, right?
> > > > 
> > > 
> > > They are PCIe form factor Coprocessors plugged into the host.
> > > 
> > > > Maybe we should have something more promintent than drivers/misc for
> > > > this, then? Like drivers/multicomputer?
> > > > 
> > > 
> > > multicomputer" is an interesting name for these kind of devices but has
> > > several issues:
> > > a) The definition I found for multicomputer online was "A computer made
> > > up of several computers. The term generally refers to an architecture in
> > > which each processor has its own memory rather than multiple processors
> > > with a shared memory. A multicore computer, although it sounds similar,
> > > would not be a multicomputer because the multiple cores share a common
> > > memory." Intel MIC X100 devices typically have upto 244 CPUs (61 cores)
> > > on the card sharing common card memory so multicomputer would not be
> > > accurate based on this definition.
> > 
> > Well... you have your "host" computer, and than (potentially several)
> > Intel MIC devices, which are basically separate computers. So X100 is
> > not a multicomputer, but machine with several X100 cards certainly is
> > multicomputer.
> > 
> > > b) X100 MIC devices have always been referred to Coprocessors and never
> > > as multicomputers in product specifications @
> > > http://software.intel.com/en-us/mic-developer
> > 
> > Coprocessor sounds like i487, but why not.
> > 
> > > c) multicomputer is a very long path name.
> > 
> > Agreed it is long. drivers/coproc? 
> > 
> > [I guess we'll get similar hardware from different vendors in
> > future. It would make sense having it at common place.]
> > 
> 
> drivers/coproc is a good, short suggestion. Intel MIC X100 devices are
> likely unique since they can run a general purpose OS in a PCIe form
> factor Coprocessor plugged to the host. This might result in MIC
> potentially being the only driver under drivers/coproc till another
> general purpose Coprocessor comes along. Is it recommended to create a
> new driver directory (drivers/coproc) in anticipation of future devices?
> Do you think it would be better if we revive this discussion, once
> another Coprocessor with similar capabilities comes along?

Creating a new driver directory for one device that may never have a
similar device to share that directory seems a bit overkill.  git mv is
simple and quick to rearrange the directory structure later if the need
arises (with the appropriate Kconfig tweakage).

-PJ

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