On Wed, Dec 09, 2015 at 07:39:56PM +0000, Dave Gordon wrote:
> On 09/12/15 16:15, Tvrtko Ursulin wrote:
> >
> >Hi,
> >
> >On 09/12/15 12:46, ankitprasad.r.sharma@xxxxxxxxx wrote:
> >>From: Ankitprasad Sharma <ankitprasad.r.sharma@xxxxxxxxx>
> >>
> >>This patch adds support for extending the pread/pwrite functionality
> >>for objects not backed by shmem. The access will be made through
> >>gtt interface. This will cover objects backed by stolen memory as well
> >>as other non-shmem backed objects.
> >>
> >>v2: Drop locks around slow_user_access, prefault the pages before
> >>access (Chris)
> >>
> >>v3: Rebased to the latest drm-intel-nightly (Ankit)
> >>
> >>v4: Moved page base & offset calculations outside the copy loop,
> >>corrected data types for size and offset variables, corrected if-else
> >>braces format (Tvrtko/kerneldocs)
> >>
> >>v5: Enabled pread/pwrite for all non-shmem backed objects including
> >>without tiling restrictions (Ankit)
> >>
> >>v6: Using pwrite_fast for non-shmem backed objects as well (Chris)
> >>
> >>v7: Updated commit message, Renamed i915_gem_gtt_read to
> >>i915_gem_gtt_copy,
> >>added pwrite slow path for non-shmem backed objects (Chris/Tvrtko)
> >>
> >>v8: Updated v7 commit message, mutex unlock around pwrite slow path for
> >>non-shmem backed objects (Tvrtko)
> >>
> >>Testcase: igt/gem_stolen
> >>
> >>Signed-off-by: Ankitprasad Sharma <ankitprasad.r.sharma@xxxxxxxxx>
> >>---
> >> drivers/gpu/drm/i915/i915_gem.c | 151
> >>+++++++++++++++++++++++++++++++++-------
> >> 1 file changed, 127 insertions(+), 24 deletions(-)
> >>
> >>diff --git a/drivers/gpu/drm/i915/i915_gem.c
> >>b/drivers/gpu/drm/i915/i915_gem.c
> >>index ed97de6..68ed67a 100644
> >>--- a/drivers/gpu/drm/i915/i915_gem.c
> >>+++ b/drivers/gpu/drm/i915/i915_gem.c
> >>@@ -614,6 +614,99 @@ shmem_pread_slow(struct page *page, int
> >>shmem_page_offset, int page_length,
> >> return ret ? - EFAULT : 0;
> >> }
> >>
> >>+static inline uint64_t
> >>+slow_user_access(struct io_mapping *mapping,
> >>+ uint64_t page_base, int page_offset,
> >>+ char __user *user_data,
> >>+ int length, bool pwrite)
> >>+{
> >>+ void __iomem *vaddr_inatomic;
> >>+ void *vaddr;
> >>+ uint64_t unwritten;
> >>+
> >>+ vaddr_inatomic = io_mapping_map_wc(mapping, page_base);
> >>+ /* We can use the cpu mem copy function because this is X86. */
> >>+ vaddr = (void __force *)vaddr_inatomic + page_offset;
> >>+ if (pwrite)
> >>+ unwritten = __copy_from_user(vaddr, user_data, length);
> >>+ else
> >>+ unwritten = __copy_to_user(user_data, vaddr, length);
> >>+
> >>+ io_mapping_unmap(vaddr_inatomic);
> >>+ return unwritten;
> >>+}
> >>+
> >>+static int
> >>+i915_gem_gtt_copy(struct drm_device *dev,
> >>+ struct drm_i915_gem_object *obj, uint64_t size,
> >>+ uint64_t data_offset, uint64_t data_ptr)
> >>+{
> >>+ struct drm_i915_private *dev_priv = dev->dev_private;
> >>+ char __user *user_data;
> >>+ uint64_t remain;
> >>+ uint64_t offset, page_base;
> >>+ int page_offset, page_length, ret = 0;
> >>+
> >>+ ret = i915_gem_obj_ggtt_pin(obj, 0, PIN_MAPPABLE);
> >>+ if (ret)
> >>+ goto out;
> >>+
> >>+ ret = i915_gem_object_set_to_gtt_domain(obj, false);
> >>+ if (ret)
> >>+ goto out_unpin;
> >>+
> >>+ ret = i915_gem_object_put_fence(obj);
> >>+ if (ret)
> >>+ goto out_unpin;
> >>+
> >>+ user_data = to_user_ptr(data_ptr);
> >>+ remain = size;
> >>+ offset = i915_gem_obj_ggtt_offset(obj) + data_offset;
> >>+
> >>+ mutex_unlock(&dev->struct_mutex);
> >>+ if (likely(!i915.prefault_disable))
> >>+ ret = fault_in_multipages_writeable(user_data, remain);
> >>+
> >>+ /*
> >>+ * page_offset = offset within page
> >>+ * page_base = page offset within aperture
> >>+ */
> >>+ page_offset = offset_in_page(offset);
> >>+ page_base = offset & PAGE_MASK;
> >>+
> >>+ while (remain > 0) {
> >>+ /* page_length = bytes to copy for this page */
> >>+ page_length = remain;
> >>+ if ((page_offset + remain) > PAGE_SIZE)
> >>+ page_length = PAGE_SIZE - page_offset;
> >>+
> >>+ /* This is a slow read/write as it tries to read from
> >>+ * and write to user memory which may result into page
> >>+ * faults
> >>+ */
> >>+ ret = slow_user_access(dev_priv->gtt.mappable, page_base,
> >>+ page_offset, user_data,
> >>+ page_length, false);
> >>+
> >>+ if (ret) {
> >>+ ret = -EFAULT;
> >>+ break;
> >>+ }
> >>+
> >>+ remain -= page_length;
> >>+ user_data += page_length;
> >>+ page_base += page_length;
> >>+ page_offset = 0;
> >>+ }
> >>+
> >>+ mutex_lock(&dev->struct_mutex);
> >>+
> >>+out_unpin:
> >>+ i915_gem_object_ggtt_unpin(obj);
> >>+out:
> >>+ return ret;
> >>+}
> >>+
> >> static int
> >> i915_gem_shmem_pread(struct drm_device *dev,
> >> struct drm_i915_gem_object *obj,
> >>@@ -737,17 +830,14 @@ i915_gem_pread_ioctl(struct drm_device *dev,
> >>void *data,
> >> goto out;
> >> }
> >>
> >>- /* prime objects have no backing filp to GEM pread/pwrite
> >>- * pages from.
> >>- */
> >>- if (!obj->base.filp) {
> >>- ret = -EINVAL;
> >>- goto out;
> >>- }
> >>-
> >> trace_i915_gem_object_pread(obj, args->offset, args->size);
> >>
> >>- ret = i915_gem_shmem_pread(dev, obj, args, file);
> >>+ /* pread for non shmem backed objects */
> >>+ if (!obj->base.filp && obj->tiling_mode == I915_TILING_NONE)
> >>+ ret = i915_gem_gtt_copy(dev, obj, args->size,
> >>+ args->offset, args->data_ptr);
> >>+ else
> >>+ ret = i915_gem_shmem_pread(dev, obj, args, file);
> >
> >Hm, it will end up calling i915_gem_shmem_pread for non-shmem backed
> >objects if tiling is set. Sounds wrong to me unless I am missing something?
>
> Which GEM objects have obj->base.filp set? Is it ONLY regular gtt-type
obj->base.filp is for shmem backed stuff. gtt is irrelevant for backing
storage, well except if you can't read the shmem stuff directly with the
cpu the only way is to go through a gtt device mapping.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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