[vfio-users] Framebuffer intercept: is it possible?

[Wynter Woods]

I've been wondering about this a lot lately. Possibly by rewriting nouveau/any other gpu driver to support a framebuffer/read only state? I realize there would end up being a few differences between how Windows handles state and how we handle state on Linux but it shouldn't be so vastly different that it wouldn't be usable.




My knowledge of gpu driver architecture is limited though so take these thoughts with a grain of salt.



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On Tue, Sep 15, 2015 at 9:15 AM, Blank Field <ihatethisfield at gmail.com>
wrote:

> Just as i've been thinking.
> So yeah, map the device memory and find the frame buffer in it.
> On Sep 15, 2015 6:13 PM, "Alex Williamson" <alex.williamson at redhat.com>
> wrote:
>> On Tue, 2015-09-15 at 13:20 +0200, Leonhard Preis wrote:
>> > Hi!
>> >
>> > Since the card outputs the signal directly to the monitor, never passing
>> > through the domain of the host that is very unlikely. Only thing I could
>> > imagine is that you could find a way to access the cards memory and grab
>> > something there but that’s not the same thing, right?
>>
>> Yes, this is how you'd need to do it and it is theoretically possible.
>> A privileged user in the host could mmap device memory and read from it
>> (writing is most likely a very bad idea).  I don't know enough about the
>> internal operation of a graphics card, but I assume the framebuffer
>> would be accessible or could be pieced together if the user had
>> sufficient knowledge of the programming model of the card.
>>
>> > Am 15.09.2015, 10:01 Uhr, schrieb francesco dicarlo
>> > <evilsephiroth at gmail.com>:
>> >
>> > > Reallly interested in this. It would be a good way to analyse also
>> > > performance.
>> > >
>> > > 2015-09-15 9:09 GMT+02:00 Blank Field <ihatethisfield at gmail.com>:
>> > >>
>> > >> Is it theoretically possible to capture the video output of the VM's
>> > >> p-t'd GPU using some host facilities?
>> > >> It would be extra awesome to be able to capture exactly what you see
>> on
>> > >> the screen, like any stuttering, corruption, directX shaders and
>> > >> accelerated video playback.
>> > >>
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>> >
>> >
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