[Intel-gfx] [PATCH] drm/i915/gem: Require per-engine reset support for non-persistent contexts

[Joonas Lahtinen]

Quoting Chris Wilson (2020-01-30 18:45:53)
> To enable non-persistent contexts, we require a means of cancelling any
> inflight work from that context. This is first done "gracefully" by
> using preemption to kick the active context off the engine, and then
> forcefully by resetting the engine if it is active. If we are unable to
> reset the engine to remove hostile userspace, we should not allow
> userspace to opt into using non-persistent contexts.
> 
> Fixes: a0e047156cde ("drm/i915/gem: Make context persistence optional")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: Jon Bloomfield <jon.bloomfield at intel.com>

Maybe worth noting that we might still ultimately end up at using
the sledge hammer called full GPU reset, in the rare cases when
engine reset fails. But it makes sense to avoid the situation
when it's guaranteed to be attempted.

Avoiding collateral damage is a worthy motive for the long
running compute cases.

Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>

Regards, Joonas