drm/i915: drop gtt slowpath

With the proper prefault, it's extremely unlikely that we fall back
to the gtt slowpath.

So just kill it and use the shmem_pwrite path as fallback.

To further clean up the code, move the preparatory gem calls into the
respective pwrite functions. This way the gtt_fast->shmem fallback
is much more obvious.

Tested-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 30 insertions, 153 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index b253257c028e..23f1a6bcee73 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -484,30 +484,6 @@ fast_user_write(struct io_mapping *mapping,
         return unwritten;
 }
 
-/* Here's the write path which can sleep for
- * page faults
- */
-
-static inline void
-slow_kernel_write(struct io_mapping *mapping,
-                  loff_t gtt_base, int gtt_offset,
-                  struct page *user_page, int user_offset,
-                  int length)
-{
-        char __iomem *dst_vaddr;
-        char *src_vaddr;
-
-        dst_vaddr = io_mapping_map_wc(mapping, gtt_base);
-        src_vaddr = kmap(user_page);
-
-        memcpy_toio(dst_vaddr + gtt_offset,
-                    src_vaddr + user_offset,
-                    length);
-
-        kunmap(user_page);
-        io_mapping_unmap(dst_vaddr);
-}
-
 /**
  * This is the fast pwrite path, where we copy the data directly from the
  * user into the GTT, uncached.
@@ -522,7 +498,19 @@ i915_gem_gtt_pwrite_fast(struct drm_device *dev,
         ssize_t remain;
         loff_t offset, page_base;
         char __user *user_data;
-        int page_offset, page_length;
+        int page_offset, page_length, ret;
+
+        ret = i915_gem_object_pin(obj, 0, true);
+        if (ret)
+                goto out;
+
+        ret = i915_gem_object_set_to_gtt_domain(obj, true);
+        if (ret)
+                goto out_unpin;
+
+        ret = i915_gem_object_put_fence(obj);
+        if (ret)
+                goto out_unpin;
 
         user_data = (char __user *) (uintptr_t) args->data_ptr;
         remain = args->size;
@@ -547,112 +535,19 @@ i915_gem_gtt_pwrite_fast(struct drm_device *dev,
                  * retry in the slow path.
                  */
                 if (fast_user_write(dev_priv->mm.gtt_mapping, page_base,
-                                    page_offset, user_data, page_length))
-                        return -EFAULT;
+                                    page_offset, user_data, page_length)) {
+                        ret = -EFAULT;
+                        goto out_unpin;
+                }
 
                 remain -= page_length;
                 user_data += page_length;
                 offset += page_length;
         }
 
-        return 0;
-}
-
-/**
- * This is the fallback GTT pwrite path, which uses get_user_pages to pin
- * the memory and maps it using kmap_atomic for copying.
- *
- * This code resulted in x11perf -rgb10text consuming about 10% more CPU
- * than using i915_gem_gtt_pwrite_fast on a G45 (32-bit).
- */
-static int
-i915_gem_gtt_pwrite_slow(struct drm_device *dev,
-                         struct drm_i915_gem_object *obj,
-                         struct drm_i915_gem_pwrite *args,
-                         struct drm_file *file)
-{
-        drm_i915_private_t *dev_priv = dev->dev_private;
-        ssize_t remain;
-        loff_t gtt_page_base, offset;
-        loff_t first_data_page, last_data_page, num_pages;
-        loff_t pinned_pages, i;
-        struct page **user_pages;
-        struct mm_struct *mm = current->mm;
-        int gtt_page_offset, data_page_offset, data_page_index, page_length;
-        int ret;
-        uint64_t data_ptr = args->data_ptr;
-
-        remain = args->size;
-
-        /* Pin the user pages containing the data.  We can't fault while
-         * holding the struct mutex, and all of the pwrite implementations
-         * want to hold it while dereferencing the user data.
-         */
-        first_data_page = data_ptr / PAGE_SIZE;
-        last_data_page = (data_ptr + args->size - 1) / PAGE_SIZE;
-        num_pages = last_data_page - first_data_page + 1;
-
-        user_pages = drm_malloc_ab(num_pages, sizeof(struct page *));
-        if (user_pages == NULL)
-                return -ENOMEM;
-
-        mutex_unlock(&dev->struct_mutex);
-        down_read(&mm->mmap_sem);
-        pinned_pages = get_user_pages(current, mm, (uintptr_t)args->data_ptr,
-                                      num_pages, 0, 0, user_pages, NULL);
-        up_read(&mm->mmap_sem);
-        mutex_lock(&dev->struct_mutex);
-        if (pinned_pages < num_pages) {
-                ret = -EFAULT;
-                goto out_unpin_pages;
-        }
-
-        ret = i915_gem_object_set_to_gtt_domain(obj, true);
-        if (ret)
-                goto out_unpin_pages;
-
-        ret = i915_gem_object_put_fence(obj);
-        if (ret)
-                goto out_unpin_pages;
-
-        offset = obj->gtt_offset + args->offset;
-
-        while (remain > 0) {
-                /* Operation in this page
-                 *
-                 * gtt_page_base = page offset within aperture
-                 * gtt_page_offset = offset within page in aperture
-                 * data_page_index = page number in get_user_pages return
-                 * data_page_offset = offset with data_page_index page.
-                 * page_length = bytes to copy for this page
-                 */
-                gtt_page_base = offset & PAGE_MASK;
-                gtt_page_offset = offset_in_page(offset);
-                data_page_index = data_ptr / PAGE_SIZE - first_data_page;
-                data_page_offset = offset_in_page(data_ptr);
-
-                page_length = remain;
-                if ((gtt_page_offset + page_length) > PAGE_SIZE)
-                        page_length = PAGE_SIZE - gtt_page_offset;
-                if ((data_page_offset + page_length) > PAGE_SIZE)
-                        page_length = PAGE_SIZE - data_page_offset;
-
-                slow_kernel_write(dev_priv->mm.gtt_mapping,
-                                  gtt_page_base, gtt_page_offset,
-                                  user_pages[data_page_index],
-                                  data_page_offset,
-                                  page_length);
-
-                remain -= page_length;
-                offset += page_length;
-                data_ptr += page_length;
-        }
-
-out_unpin_pages:
-        for (i = 0; i < pinned_pages; i++)
-                page_cache_release(user_pages[i]);
-        drm_free_large(user_pages);
-
+out_unpin:
+        i915_gem_object_unpin(obj);
+out:
         return ret;
 }
 
@@ -671,6 +566,10 @@ i915_gem_shmem_pwrite(struct drm_device *dev,
         int hit_slowpath = 0;
         int release_page;
 
+        ret = i915_gem_object_set_to_cpu_domain(obj, 1);
+        if (ret)
+                return ret;
+
         user_data = (char __user *) (uintptr_t) args->data_ptr;
         remain = args->size;
 
@@ -814,6 +713,7 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
 
         trace_i915_gem_object_pwrite(obj, args->offset, args->size);
 
+        ret = -EFAULT;
         /* We can only do the GTT pwrite on untiled buffers, as otherwise
          * it would end up going through the fenced access, and we'll get
          * different detiling behavior between reading and writing.
@@ -828,37 +728,14 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
         if (obj->gtt_space &&
             obj->cache_level == I915_CACHE_NONE &&
             obj->base.write_domain != I915_GEM_DOMAIN_CPU) {
-                ret = i915_gem_object_pin(obj, 0, true);
-                if (ret)
-                        goto out;
-
-                ret = i915_gem_object_set_to_gtt_domain(obj, true);
-                if (ret)
-                        goto out_unpin;
-
-                ret = i915_gem_object_put_fence(obj);
-                if (ret)
-                        goto out_unpin;
-
                 ret = i915_gem_gtt_pwrite_fast(dev, obj, args, file);
-                if (ret == -EFAULT)
-                        ret = i915_gem_gtt_pwrite_slow(dev, obj, args, file);
-
-out_unpin:
-                i915_gem_object_unpin(obj);
-
-                if (ret != -EFAULT)
-                        goto out;
-                /* Fall through to the shmfs paths because the gtt paths might
-                 * fail with non-page-backed user pointers (e.g. gtt mappings
-                 * when moving data between textures). */
+                /* Note that the gtt paths might fail with non-page-backed user
+                 * pointers (e.g. gtt mappings when moving data between
+                 * textures). Fallback to the shmem path in that case. */
         }
 
-        ret = i915_gem_object_set_to_cpu_domain(obj, 1);
-        if (ret)
-                goto out;
-
-        ret = i915_gem_shmem_pwrite(dev, obj, args, file);
+        if (ret == -EFAULT)
+                ret = i915_gem_shmem_pwrite(dev, obj, args, file);
 
 out:
         drm_gem_object_unreference(&obj->base);