drm/i915: Move ioremap_wc tracking onto VMA

By tracking the iomapping on the VMA itself, we can share that area
between multiple users. Also by only revoking the iomapping upon
unbinding from the mappable portion of the GGTT, we can keep that iomap
across multiple invocations (e.g. execlists context pinning).

Note that by moving the iounnmap tracking to the VMA, we actually end up
fixing a leak of the iomapping in intel_fbdev.

v1.5: Rebase prompted by Tvrtko
v2: Drop dev_priv parameter, we can recover the i915_ggtt from the vma.
v3: Move handling of ioremap space exhaustion to vmap_purge and also
allow vmallocs to recover old iomaps. Add Tvrtko's kerneldoc.
v4: Fix a use-after-free in shrinker and rearrange i915_vma_iomap
v5: Back to i915_vm_to_ggtt
v6: Use i915_vma_pin_iomap and i915_vma_unpin_iomap to mark critical
sections and ensure the VMA cannot be reaped whilst mapped.
v7: Move i915_vma_iounmap so that consumers of the API are not tempted,
and add iomem annotations

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461833819-3991-5-git-send-email-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem.c

@@ -3341,6 +3341,17 @@ static void i915_gem_object_finish_gtt(struct drm_i915_gem_object *obj)
 					    old_write_domain);
 }
 
+static void __i915_vma_iounmap(struct i915_vma *vma)
+{
+	GEM_BUG_ON(vma->pin_count);
+
+	if (vma->iomap == NULL)
+		return;
+
+	io_mapping_unmap(vma->iomap);
+	vma->iomap = NULL;
+}
+
 static int __i915_vma_unbind(struct i915_vma *vma, bool wait)
 {
 	struct drm_i915_gem_object *obj = vma->obj;
@@ -3373,6 +3384,8 @@ static int __i915_vma_unbind(struct i915_vma *vma, bool wait)
 		ret = i915_gem_object_put_fence(obj);
 		if (ret)
 			return ret;
+
+		__i915_vma_iounmap(vma);
 	}
 
 	trace_i915_vma_unbind(vma);

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -3640,3 +3640,29 @@ i915_ggtt_view_size(struct drm_i915_gem_object *obj,
 		return obj->base.size;
 	}
 }
+
+void __iomem *i915_vma_pin_iomap(struct i915_vma *vma)
+{
+	void __iomem *ptr;
+
+	lockdep_assert_held(&vma->vm->dev->struct_mutex);
+	if (WARN_ON(!vma->obj->map_and_fenceable))
+		return ERR_PTR(-ENODEV);
+
+	GEM_BUG_ON(!vma->is_ggtt);
+	GEM_BUG_ON((vma->bound & GLOBAL_BIND) == 0);
+
+	ptr = vma->iomap;
+	if (ptr == NULL) {
+		ptr = io_mapping_map_wc(i915_vm_to_ggtt(vma->vm)->mappable,
+					vma->node.start,
+					vma->node.size);
+		if (ptr == NULL)
+			return ERR_PTR(-ENOMEM);
+
+		vma->iomap = ptr;
+	}
+
+	vma->pin_count++;
+	return ptr;
+}

drivers/gpu/drm/i915/i915_gem_gtt.h

@@ -34,6 +34,8 @@
 #ifndef __I915_GEM_GTT_H__
 #define __I915_GEM_GTT_H__
 
+#include <linux/io-mapping.h>
+
 struct drm_i915_file_private;
 
 typedef uint32_t gen6_pte_t;
@@ -175,6 +177,7 @@ struct i915_vma {
 	struct drm_mm_node node;
 	struct drm_i915_gem_object *obj;
 	struct i915_address_space *vm;
+	void __iomem *iomap;
 
 	/** Flags and address space this VMA is bound to */
 #define GLOBAL_BIND	(1<<0)
@@ -559,4 +562,36 @@ size_t
 i915_ggtt_view_size(struct drm_i915_gem_object *obj,
 		    const struct i915_ggtt_view *view);
 
+/**
+ * i915_vma_pin_iomap - calls ioremap_wc to map the GGTT VMA via the aperture
+ * @vma: VMA to iomap
+ *
+ * The passed in VMA has to be pinned in the global GTT mappable region.
+ * An extra pinning of the VMA is acquired for the return iomapping,
+ * the caller must call i915_vma_unpin_iomap to relinquish the pinning
+ * after the iomapping is no longer required.
+ *
+ * Callers must hold the struct_mutex.
+ *
+ * Returns a valid iomapped pointer or ERR_PTR.
+ */
+void __iomem *i915_vma_pin_iomap(struct i915_vma *vma);
+
+/**
+ * i915_vma_unpin_iomap - unpins the mapping returned from i915_vma_iomap
+ * @vma: VMA to unpin
+ *
+ * Unpins the previously iomapped VMA from i915_vma_pin_iomap().
+ *
+ * Callers must hold the struct_mutex. This function is only valid to be
+ * called on a VMA previously iomapped by the caller with i915_vma_pin_iomap().
+ */
+static inline void i915_vma_unpin_iomap(struct i915_vma *vma)
+{
+	lockdep_assert_held(&vma->vm->dev->struct_mutex);
+	GEM_BUG_ON(vma->pin_count == 0);
+	GEM_BUG_ON(vma->iomap == NULL);
+	vma->pin_count--;
+}
+
 #endif

drivers/gpu/drm/i915/i915_gem_shrinker.c

@@ -386,17 +386,33 @@ i915_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr
 	struct drm_i915_private *dev_priv =
 		container_of(nb, struct drm_i915_private, mm.vmap_notifier);
 	struct shrinker_lock_uninterruptible slu;
-	unsigned long freed_pages;
+	struct i915_vma *vma, *next;
+	unsigned long freed_pages = 0;
+	int ret;
 
 	if (!i915_gem_shrinker_lock_uninterruptible(dev_priv, &slu, 5000))
 		return NOTIFY_DONE;
 
-	freed_pages = i915_gem_shrink(dev_priv, -1UL,
-				      I915_SHRINK_BOUND |
-				      I915_SHRINK_UNBOUND |
-				      I915_SHRINK_ACTIVE |
-				      I915_SHRINK_VMAPS);
+	/* Force everything onto the inactive lists */
+	ret = i915_gpu_idle(dev_priv->dev);
+	if (ret)
+		goto out;
+
+	freed_pages += i915_gem_shrink(dev_priv, -1UL,
+				       I915_SHRINK_BOUND |
+				       I915_SHRINK_UNBOUND |
+				       I915_SHRINK_ACTIVE |
+				       I915_SHRINK_VMAPS);
+
+	/* We also want to clear any cached iomaps as they wrap vmap */
+	list_for_each_entry_safe(vma, next,
+				 &dev_priv->ggtt.base.inactive_list, vm_link) {
+		unsigned long count = vma->node.size >> PAGE_SHIFT;
+		if (vma->iomap && i915_vma_unbind(vma) == 0)
+			freed_pages += count;
+	}
 
+out:
 	i915_gem_shrinker_unlock_uninterruptible(dev_priv, &slu);
 
 	*(unsigned long *)ptr += freed_pages;

drivers/gpu/drm/i915/intel_fbdev.c

@@ -186,9 +186,11 @@ static int intelfb_create(struct drm_fb_helper *helper,
 	struct i915_ggtt *ggtt = &dev_priv->ggtt;
 	struct fb_info *info;
 	struct drm_framebuffer *fb;
+	struct i915_vma *vma;
 	struct drm_i915_gem_object *obj;
-	int size, ret;
 	bool prealloc = false;
+	void *vaddr;
+	int ret;
 
 	if (intel_fb &&
 	    (sizes->fb_width > intel_fb->base.width ||
@@ -214,7 +216,6 @@ static int intelfb_create(struct drm_fb_helper *helper,
 	}
 
 	obj = intel_fb->obj;
-	size = obj->base.size;
 
 	mutex_lock(&dev->struct_mutex);
 
@@ -244,22 +245,23 @@ static int intelfb_create(struct drm_fb_helper *helper,
 	info->flags = FBINFO_DEFAULT | FBINFO_CAN_FORCE_OUTPUT;
 	info->fbops = &intelfb_ops;
 
+	vma = i915_gem_obj_to_ggtt(obj);
+
 	/* setup aperture base/size for vesafb takeover */
 	info->apertures->ranges[0].base = dev->mode_config.fb_base;
 	info->apertures->ranges[0].size = ggtt->mappable_end;
 
-	info->fix.smem_start = dev->mode_config.fb_base + i915_gem_obj_ggtt_offset(obj);
-	info->fix.smem_len = size;
+	info->fix.smem_start = dev->mode_config.fb_base + vma->node.start;
+	info->fix.smem_len = vma->node.size;
 
-	info->screen_base =
-		ioremap_wc(ggtt->mappable_base + i915_gem_obj_ggtt_offset(obj),
-			   size);
-	if (!info->screen_base) {
+	vaddr = i915_vma_pin_iomap(vma);
+	if (IS_ERR(vaddr)) {
 		DRM_ERROR("Failed to remap framebuffer into virtual memory\n");
-		ret = -ENOSPC;
+		ret = PTR_ERR(vaddr);
 		goto out_destroy_fbi;
 	}
-	info->screen_size = size;
+	info->screen_base = vaddr;
+	info->screen_size = vma->node.size;
 
 	/* This driver doesn't need a VT switch to restore the mode on resume */
 	info->skip_vt_switch = true;