Re: [Xen-devel] Fwd: Mouse Click and Context Switch Question

["Sujata Doshi" <sujatadoshi@xxxxxxxxx>]

Hi
Thank you very much for your response --- yes we are using full
virtualization with a Windows Guest OS -- thanks for pointing out
about the qemu-dm

On the context switching front, I was wondering if there is a way to
leverage the memory information i.e every new process creation should
have a new page directory and its own address space associated with it
right ?-- so is there a way to use that information to figure out
which was the current process ? --- I agree, we would still need
application specific information to map the application to the process
-- but can the context switching be inferred by the VMM on a process
level without asking the guest OS?
Thanks again
Sujata


On 10/13/06, Petersson, Mats <Mats.Petersson@xxxxxxx> wrote:
> > -----Original Message-----
> > From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
> > [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of
> > Sujata Doshi
> > Sent: 13 October 2006 17:28
> > To: xen-devel@xxxxxxxxxxxxxxxxxxx
> > Subject: [Xen-devel] Fwd: Mouse Click and Context Switch Question
> >
> > Hi
> > I wasn't sure if the email below went through , since I was not
> > subscribed to the list. Would appreciate your response.
> > Thanks
> > Sujata
> >
> > ---------- Forwarded message ----------
> > From: Sujata Doshi <sujatadoshi@xxxxxxxxx>
> > Date: Oct 13, 2006 10:37 AM
> > Subject: Mouse Click and Context Switch Question
> > To: xen-devel@xxxxxxxxxxxxxxxxxxx
> >
> >
> > Hello
> > I am starting a research project which involves using Xen. Basically
> > we would like to monitor the input to an application running in the
> > guest OS . Specifically, we need to be able to figure out when an
> > input was made via a mouse click and what the coordinates of the mouse
> > pointer were on that click. If I understand correctly, on a mouse
> > click, an interrupt occurs which gets handled by the Xen VMM --- is
> > there a way of figuring out at the Xen VMM level what the coordinates
> > of the click are when this interrupt occurs ?
>
> You understand correctly on the principle of interrupts, but the actual
> mouse-movements are tracked in the mouse-handling code inside Linux
> Dom0, not in the VMM, as the VMM doesn't actually know (or care)
> anything about the mouse as a device, just about forwarding the
> interrupt to the rightfull owner.
>
> If you know what application you want to track, and you're able to hack
> some code, I'd suggest that you go modify the X-windows code (such as
> XFree86) to track where the mouse-clicks are forwarded to the
> application. Since X-windows knows which application it forwards what
> information to, it's the "perfect" place to do this [from my
> understanding of the subject - I could of course be missing some
> important factor that isn't apparent from the above brief description].
>
> > I understand this would also involve figuring out when a context
> > switch occurs to that particular application so that we can grab the
> > right mouse click. Is there an easy way to figure this context switch
> > out ?
>
> The VMM scheduler is not per process but per virtual machine, so the
> application level would have to be understood by the operating system
> running on top of Xen, as Xen doesn't actually know what application (if
> any) is running at any given time, only the Linux kernel (typial case)
> that is running on top of Xen will know this.
> >
> > I would appreciate if you could guide me with the above queries and
> > also which files in the Xen source I should be looking at to achieve
> > this task.
>
> I could theoretically help you with any Xen-files, but I don't think
> that's the right approach in the first place - you want to be working
> further up in the architecture to have access to the "current
> application".
>
> [Note: this is assuming that we're talking about para-virtualized
> clients. In the case of a full-virtualized guest [HVM, VT/AMD-V], such
> as a Windows guest, there is a possibility that you could follow the
> mouse within the qemu-dm [the device model that generates the virtual
> mouse], and use that information to record where the mouse moves to.
> However, it's still impossible to understand which application is
> running at that particular point in time - again, you need to have OS to
> help you with that].
>
> --
> Mats
> > Thank you very much for your help
> > Sujata
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-devel
> >
> >
> >
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