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

[Chris Wilson]

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>
---
 drivers/gpu/drm/i915/gem/i915_gem_context.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index 86eef1bcfcb3..c8417fe3f32c 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -565,6 +565,10 @@ static int __context_set_persistence(struct i915_gem_context *ctx, bool state)
 		if (!(ctx->i915->caps.scheduler & I915_SCHEDULER_CAP_PREEMPTION))
 			return -ENODEV;
 
+		/* If the cancel fails, we then need to reset, cleanly! */
+		if (!intel_has_reset_engine(ctx->gt))
+			return -ENODEV;
+
 		i915_gem_context_clear_persistence(ctx);
 	}
 
-- 
2.25.0