--- Thomas Hellström <[EMAIL PROTECTED]> wrote:
> Keith Whitwell wrote:
>
> The typical case here:
>
> I want a DRI client to flip a video frame to screen, using a hardware
> entity called the HQV. This is a rather time critical operation. To do
> this I have to take the hardware lock.
>
> While this is happening, another thread is waiting for the mpeg decoder
> to complete a frame. To to that, this thread needs to take the hardware
> lock, wait for quiescent DMA, and then wait for the mpeg decoder to
> signal idle. It might be that the DMA command queue does not even
> contain mpeg data. This waiting delays the frame flip enough to create a
>
> visible jump in the video.
>
> With multiple locks:
>
> The first thread checks the HQV lock, it is available and frame flipping
>
> is done immediately.
>
> The other thread meanwhile takes the MPEG engine lock, waits until the
> DMA engine has processed all MPEG commands in the command queue and then
>
> waits for the MPEG engine to be idle. DMA might still be processing 3D
> commands.
>
> Only while submitting command buffer data. This will hopefully be a very
>
> fast operation. The IOCTL copying this data to the ringbuffer will check
>
> that all locks are held for the hardware entities that the submitted
> command batch touches. The user will have to tell the IOCTL which
> entities these are, or possibly the command verifier checks this but I
> consider that an overkill since that is more of a bug-check than a
> security check.
>
Part of security is making sure authorised users can't make changes to
other users tasks. In this case killing all the tasks, by causing a
hardware fault, is a good example. It's a fackt that any user with rights
to the DRM device can use any other code or program to play with the card
or send junk into the cmd streem. The DRM should detect and prevent this,
even if it means a slight proformance loss.
Can I get an AMEN?
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