[Intel-gfx] [PATCH] drm/i915/gem: Ensure aperture exists before setting domain to GTT

[Summers, Stuart]

On Tue, 2019-11-19 at 22:08 +0000, Chris Wilson wrote:
> Quoting Stuart Summers (2019-11-19 21:30:32)
> > mmap_gtt is already covered by a check for aperture presence.
> > Also add the case to the gem_set_domain IOCTL to avoid this
> > path for unsupported platforms.
> 
> It doesn't harm either, it will just mean in a place where it is
> neither
> in the GPU nor in the CPU cache, same as it does today. The
> additional
> flushes coming out of a GTT write domain should already be elided.
> 
> It is used internally to mean precisely that...
> 
> Userspace should already be weaning itself off set-domain altogether.

But even with the weaning, shouldn't we have these checks in place for
safety? Let's say there's some platform issue with the GTT flushes and
moving ahead causes the hardware to get in a bad state. Isn't it better
to bail early? Let me know if I'm missing something obvious here
though.

Thanks,
Stuart

> -Chris
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