[PATCH v5 1/1] drm/doc: Document DRM device reset expectations

[Marek Olšák]

On Tue, Jun 27, 2023 at 5:31 PM André Almeida <andrealmeid at igalia.com>
wrote:

> Hi Marek,
>
> Em 27/06/2023 15:57, Marek Olšák escreveu:
> > On Tue, Jun 27, 2023, 09:23 André Almeida <andrealmeid at igalia.com
> > <mailto:andrealmeid at igalia.com>> wrote:
> >
> >     +User Mode Driver
> >     +----------------
> >     +
> >     +The UMD should check before submitting new commands to the KMD if
> >     the device has
> >     +been reset, and this can be checked more often if the UMD requires
> >     it. After
> >     +detecting a reset, UMD will then proceed to report it to the
> >     application using
> >     +the appropriate API error code, as explained in the section below
> about
> >     +robustness.
> >
> >
> > The UMD won't check the device status before every command submission
> > due to ioctl overhead. Instead, the KMD should skip command submission
> > and return an error that it was skipped.
>
> I wrote like this because when reading the source code for
> vk::check_status()[0] and Gallium's si_flush_gfx_cs()[1], I was under
> the impression that UMD checks the reset status before every
> submission/flush.
>

It only does that before every command submission when the context is
robust. When it's not robust, radeonsi doesn't do anything.


>
> Is your comment about of how things are currently implemented, or how
> they would ideally work? Either way I can apply your suggestion, I just
> want to make it clear.
>

Yes. Ideally, we would get the reply whether the context is lost from the
CS ioctl. This is not currently implemented.

Marek


>
> [0]
>
> https://elixir.bootlin.com/mesa/mesa-23.1.3/source/src/vulkan/runtime/vk_device.h#L142
> [1]
>
> https://elixir.bootlin.com/mesa/mesa-23.1.3/source/src/gallium/drivers/radeonsi/si_gfx_cs.c#L83
>
> >
> > The only case where that won't be applicable is user queues where
> > drivers don't call into the kernel to submit work, but they do call into
> > the kernel to create a dma_fence. In that case, the call to create a
> > dma_fence can fail with an error.
> >
> > Marek
>
>
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