From a6508ded2a6601fea903185034adc3622d94da0b Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Mon, 6 Feb 2017 08:45:47 +0000 Subject: [PATCH] drm/i915: Use page coloring to provide the guard page at the end of the GTT As we now mark the reserved hole (drm_mm.head_node) with the special UNEVICTABLE color, we can use the page coloring to avoid prefetching of the CS beyond the end of the GTT. Signed-off-by: Chris Wilson Link: http://patchwork.freedesktop.org/patch/msgid/20170206084547.27921-3-chris@chris-wilson.co.uk Reviewed-by: Matthew Auld --- drivers/gpu/drm/i915/i915_gem_evict.c | 10 ++++++++-- drivers/gpu/drm/i915/i915_gem_gtt.c | 19 ++++++++++++------- 2 files changed, 20 insertions(+), 9 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem_evict.c b/drivers/gpu/drm/i915/i915_gem_evict.c index a43e44e18042..6d2fcfafd3c5 100644 --- a/drivers/gpu/drm/i915/i915_gem_evict.c +++ b/drivers/gpu/drm/i915/i915_gem_evict.c @@ -253,6 +253,9 @@ int i915_gem_evict_for_node(struct i915_address_space *vm, int ret = 0; lockdep_assert_held(&vm->i915->drm.struct_mutex); + GEM_BUG_ON(!IS_ALIGNED(start, I915_GTT_PAGE_SIZE)); + GEM_BUG_ON(!IS_ALIGNED(end, I915_GTT_PAGE_SIZE)); + trace_i915_gem_evict_node(vm, target, flags); /* Retire before we search the active list. Although we have @@ -268,9 +271,11 @@ int i915_gem_evict_for_node(struct i915_address_space *vm, /* Expand search to cover neighbouring guard pages (or lack!) */ if (start > vm->start) start -= I915_GTT_PAGE_SIZE; - if (end < vm->start + vm->total) - end += I915_GTT_PAGE_SIZE; + + /* Always look at the page afterwards to avoid the end-of-GTT */ + end += I915_GTT_PAGE_SIZE; } + GEM_BUG_ON(start >= end); drm_mm_for_each_node_in_range(node, &vm->mm, start, end) { /* If we find any non-objects (!vma), we cannot evict them */ @@ -279,6 +284,7 @@ int i915_gem_evict_for_node(struct i915_address_space *vm, break; } + GEM_BUG_ON(!node->allocated); vma = container_of(node, typeof(*vma), node); /* If we are using coloring to insert guard pages between diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c index 9f1f3bfead59..850d40ec77af 100644 --- a/drivers/gpu/drm/i915/i915_gem_gtt.c +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c @@ -2718,11 +2718,16 @@ static void i915_gtt_color_adjust(const struct drm_mm_node *node, u64 *start, u64 *end) { - if (node->color != color) + if (node->allocated && node->color != color) *start += I915_GTT_PAGE_SIZE; + /* Also leave a space between the unallocated reserved node after the + * GTT and any objects within the GTT, i.e. we use the color adjustment + * to insert a guard page to prevent prefetches crossing over the + * GTT boundary. + */ node = list_next_entry(node, node_list); - if (node->allocated && node->color != color) + if (node->color != color) *end -= I915_GTT_PAGE_SIZE; } @@ -3243,14 +3248,14 @@ int i915_ggtt_init_hw(struct drm_i915_private *dev_priv) INIT_LIST_HEAD(&dev_priv->vm_list); - /* Subtract the guard page before address space initialization to - * shrink the range used by drm_mm. + /* Note that we use page colouring to enforce a guard page at the + * end of the address space. This is required as the CS may prefetch + * beyond the end of the batch buffer, across the page boundary, + * and beyond the end of the GTT if we do not provide a guard. */ mutex_lock(&dev_priv->drm.struct_mutex); - ggtt->base.total -= I915_GTT_PAGE_SIZE; i915_address_space_init(&ggtt->base, dev_priv, "[global]"); - ggtt->base.total += I915_GTT_PAGE_SIZE; - if (!HAS_LLC(dev_priv)) + if (!HAS_LLC(dev_priv) && !USES_PPGTT(dev_priv)) ggtt->base.mm.color_adjust = i915_gtt_color_adjust; mutex_unlock(&dev_priv->drm.struct_mutex);