Commit 63de1da1 authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915: Remove livelock from "do_idle_maps" vtd w/a 



A call to wait for the GT to idle from inside the put_pages fallback is
prone to cause an uninterruptible livelock. As it does not provide
adequate serialisation with new requests, simply fallback to a trivial
sleep.

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: default avatarMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201209164008.5487-1-chris@chris-wilson.co.uk
parent 338d58cf

drivers/gpu/drm/i915/i915_gem_gtt.c

+10 −15
Original line number Diff line number Diff line
@@ -55,22 +55,17 @@ int i915_gem_gtt_prepare_pages(struct drm_i915_gem_object *obj, 
void i915_gem_gtt_finish_pages(struct drm_i915_gem_object *obj,

			       struct sg_table *pages)

{

	struct drm_i915_private *dev_priv = to_i915(obj->base.dev);

	struct device *kdev = &dev_priv->drm.pdev->dev;

	struct i915_ggtt *ggtt = &dev_priv->ggtt;

	struct drm_i915_private *i915 = to_i915(obj->base.dev);

	struct i915_ggtt *ggtt = &i915->ggtt;



	if (unlikely(ggtt->do_idle_maps)) {

	/* XXX This does not prevent more requests being submitted! */

		if (intel_gt_retire_requests_timeout(ggtt->vm.gt,

						     -MAX_SCHEDULE_TIMEOUT)) {

			drm_err(&dev_priv->drm,

				"Failed to wait for idle; VT'd may hang.\n");

			/* Wait a bit, in hopes it avoids the hang */

			udelay(10);

		}

	}

	if (unlikely(ggtt->do_idle_maps))

		/* Wait a bit, in the hope it avoids the hang */

		usleep_range(100, 250);



	dma_unmap_sg(kdev, pages->sgl, pages->nents, PCI_DMA_BIDIRECTIONAL);

	dma_unmap_sg(&i915->drm.pdev->dev,

		     pages->sgl, pages->nents,

		     PCI_DMA_BIDIRECTIONAL);

}



/**