From: KY Srinivasan <kys@microsoft.com>
To: "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        Dan Carpenter <dan.carpenter@oracle.com>
CC: "olaf@aepfle.de" <olaf@aepfle.de>,
        "jasowang@redhat.com" <jasowang@redhat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "apw@canonical.com" <apw@canonical.com>,
        "devel@linuxdriverproject.org" <devel@linuxdriverproject.org>
Subject: RE: [PATCH 1/1] Drivers: hv: Implement the file copy service
Thread-Topic: [PATCH 1/1] Drivers: hv: Implement the file copy service
Thread-Index: AQHPDMVZ9zrtMOoYp0KOm7oSIbZbR5p8AmiAgAC00tCAAByZgIAAAXcAgAAPqHA=
Date: Thu, 9 Jan 2014 21:13:05 +0000
Message-ID: <1890f66fdb9341178202866cd20d4504@BY2PR03MB299.namprd03.prod.outlook.com>
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 <20140109200921.GT30234@mwanda> <20140109201436.GA16425@kroah.com>
In-Reply-To: <20140109201436.GA16425@kroah.com>
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> -----Original Message-----
> From: gregkh@linuxfoundation.org [mailto:gregkh@linuxfoundation.org]
> Sent: Thursday, January 09, 2014 12:15 PM
> To: Dan Carpenter
> Cc: KY Srinivasan; olaf@aepfle.de; jasowang@redhat.com; linux-
> kernel@vger.kernel.org; apw@canonical.com; devel@linuxdriverproject.org
> Subject: Re: [PATCH 1/1] Drivers: hv: Implement the file copy service
> 
> On Thu, Jan 09, 2014 at 11:09:21PM +0300, Dan Carpenter wrote:
> > We've had this discussion before where you urge me to trust the host...
> >
> >  Problem: This code is racy.
> > Solution: The host will only send one message at a time.
> >
> > Now I have to audit the user space code on the host and I don't feel
> > like doing that so you win.
> >
> > I wish we had a better way to do IPC.  If kdbus were ready, that might
> > have worked for this, and it's a better solution because both sender and
> > reciever code will be written in a less trusting way.
> 
> kdbus is almost ready, it might make 3.15, depending on the result of
> work that is happening at linux.conf.au and FOSDEM.
> 
> If it would be a better solution for this, that's even more reason to
> get kdbus merged soon, no need to add something that doesn't really
> work.
> 
> But, how will kdbus help with this?  It's a userspace <-> userspace
> message transmission bus, would you want the kernel to be a receiver or
> sender here?

Greg,

The transport between the kernel and the user in this driver is a regular char device and
Vmbus is the transport between the host and the guest. As you observe, I am not sure
how kdbus would be useful.

K. Y
> 
> thanks,
> 
> greg k-h
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