[PATCH v3 0/4] Support for creating/using Stolen memory backed objects

[PATCH v3 0/4] Support for creating/using Stolen memory backed objects

[ankitprasad.r.sharma]

From: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>

This patch series adds support for creating/using Stolen memory backed
objects.

Despite being a unified memory architecture (UMA) some bits of memory
are more equal than others. In particular we have the thorny issue of
stolen memory, memory stolen from the system by the BIOS and reserved
for igfx use. Stolen memory is required for some functions of the GPU
and display engine, but in general it goes wasted. Whilst we cannot
return it back to the system, we need to find some other method for
utilising it. As we do not support direct access to the physical address
in the stolen region, it behaves like a different class of memory,
closer in kin to local GPU memory. This strongly suggests that we need a
placement model like TTM if we are to fully utilize these discrete
chunks of differing memory.

To add support for creating Stolen memory backed objects, we extend the
drm_i915_gem_create structure, by adding a new flag through which user
can specify the preference to allocate the object from stolen memory,
which if set, an attempt will be made to allocate the object from stolen
memory subject to the availability of free space in the stolen region.

This patch series adds support for clearing buffer objects via blitter
engines. This is particularly useful for clearing out the memory from
stolen region, but can also be used for other shmem allocated objects.
Also adding support for stealing purgable stolen pages, if we run out
of stolen memory when trying to allocate an object.

v2: Added support for read/write from/to objects not backed by
shmem using the pread/pwrite interface.
Also extended the current get_aperture ioctl to retrieve the
total and available size of the stolen region

v3: Removed the extended get_aperture ioctl patch 5 (to be submitted as
part of other patch series), addressed comments by Chris about pread/pwrite
for non shmem backed objects

This can be verified using IGT tests: igt/gem_create_stolen

Ankitprasad Sharma (3):
  drm/i915: Clearing buffer objects via blitter engine
  drm/i915: Support for creating Stolen memory backed objects
  drm/i915: Support for pread/pwrite from/to non shmem backed objects

Chris Wilson (1):
  drm/i915: Add support for stealing purgable stolen pages

 drivers/gpu/drm/i915/Makefile          |   1 +
 drivers/gpu/drm/i915/i915_dma.c        |   3 +
 drivers/gpu/drm/i915/i915_drv.h        |   4 +
 drivers/gpu/drm/i915/i915_gem.c        | 168 ++++++++++++++++++++++++----
 drivers/gpu/drm/i915/i915_gem_exec.c   | 197 +++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/i915_gem_stolen.c | 121 ++++++++++++++++++--
 drivers/gpu/drm/i915/intel_lrc.c       |   2 +-
 drivers/gpu/drm/i915/intel_lrc.h       |   2 +
 include/uapi/drm/i915_drm.h            |  15 +++
 9 files changed, 480 insertions(+), 33 deletions(-)
 create mode 100644 drivers/gpu/drm/i915/i915_gem_exec.c

-- 
1.9.1

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[PATCH 1/4] drm/i915: Clearing buffer objects via blitter engine

[ankitprasad.r.sharma]

From: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>

This patch adds support for clearing buffer objects via blitter
engines. This is particularly useful for clearing out the memory
from stolen region.

v2: Add support for using execlists & PPGTT

v3: Fix issues in legacy ringbuffer submission mode

testcase: igt/gem_create_stolen

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Deepak S <deepak.s at linux.intel.com>
Signed-off-by: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>
---
 drivers/gpu/drm/i915/Makefile        |   1 +
 drivers/gpu/drm/i915/i915_drv.h      |   4 +
 drivers/gpu/drm/i915/i915_gem_exec.c | 197 +++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_lrc.c     |   2 +-
 drivers/gpu/drm/i915/intel_lrc.h     |   2 +
 5 files changed, 205 insertions(+), 1 deletion(-)
 create mode 100644 drivers/gpu/drm/i915/i915_gem_exec.c

diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index a69002e..711a87d 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -25,6 +25,7 @@ i915-y += i915_cmd_parser.o \
 	  i915_gem_debug.o \
 	  i915_gem_dmabuf.o \
 	  i915_gem_evict.o \
+	  i915_gem_exec.o \
 	  i915_gem_execbuffer.o \
 	  i915_gem_gtt.o \
 	  i915_gem.o \
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index eb38cd1..21a2b1f 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2927,6 +2927,10 @@ int __must_check i915_gem_evict_something(struct drm_device *dev,
 int i915_gem_evict_vm(struct i915_address_space *vm, bool do_idle);
 int i915_gem_evict_everything(struct drm_device *dev);
 
+/* i915_gem_exec.c */
+int i915_gem_exec_clear_object(struct drm_i915_gem_object *obj,
+			       struct drm_i915_file_private *file_priv);
+
 /* belongs in i915_gem_gtt.h */
 static inline void i915_gem_chipset_flush(struct drm_device *dev)
 {
diff --git a/drivers/gpu/drm/i915/i915_gem_exec.c b/drivers/gpu/drm/i915/i915_gem_exec.c
new file mode 100644
index 0000000..224bd5f
--- /dev/null
+++ b/drivers/gpu/drm/i915/i915_gem_exec.c
@@ -0,0 +1,197 @@
+/*
+ * Copyright © 2013 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ * Authors:
+ *    Chris Wilson <chris at chris-wilson.co.uk>
+ *
+ */
+
+#include <drm/drmP.h>
+#include <drm/i915_drm.h>
+#include "i915_drv.h"
+
+#define GEN8_COLOR_BLT_CMD (2<<29 | 0x50<<22)
+
+#define BPP_8 0
+#define BPP_16 (1<<24)
+#define BPP_32 (1<<25 | 1<<24)
+
+#define ROP_FILL_COPY (0xf0 << 16)
+
+static int i915_gem_exec_flush_object(struct drm_i915_gem_object *obj,
+				      struct intel_engine_cs *ring,
+				      struct intel_context *ctx)
+{
+	int ret;
+	struct intel_ringbuffer *ringbuf = ctx->engine[ring->id].ringbuf;
+
+	ret = i915_gem_object_sync(obj, ring);
+	if (ret)
+		return ret;
+
+	if (obj->base.write_domain & I915_GEM_DOMAIN_CPU) {
+		if (i915_gem_clflush_object(obj, false))
+			i915_gem_chipset_flush(obj->base.dev);
+		obj->base.write_domain &= ~I915_GEM_DOMAIN_CPU;
+	}
+	if (obj->base.write_domain & I915_GEM_DOMAIN_GTT) {
+		wmb();
+		obj->base.write_domain &= ~I915_GEM_DOMAIN_GTT;
+	}
+
+
+	return i915.enable_execlists ?
+			logical_ring_invalidate_all_caches(ringbuf, ctx) :
+			intel_ring_invalidate_all_caches(ring);
+}
+
+static void i915_gem_exec_dirty_object(struct drm_i915_gem_object *obj,
+				       struct intel_engine_cs *ring,
+				       struct i915_address_space *vm)
+{
+	struct drm_i915_gem_request *req;
+	req = intel_ring_get_request(ring);
+
+	i915_gem_request_assign(&obj->last_write_req, req);
+	obj->base.read_domains = I915_GEM_DOMAIN_RENDER;
+	obj->base.write_domain = I915_GEM_DOMAIN_RENDER;
+	i915_vma_move_to_active(i915_gem_obj_to_vma(obj, vm), ring);
+	obj->dirty = 1;
+
+	ring->gpu_caches_dirty = true;
+}
+
+int i915_gem_exec_clear_object(struct drm_i915_gem_object *obj,
+			       struct drm_i915_file_private *file_priv)
+{
+	struct drm_device *dev = obj->base.dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct intel_engine_cs *ring;
+	struct intel_context *ctx;
+	struct intel_ringbuffer *ringbuf;
+	struct i915_address_space *vm;
+	int ret = 0;
+
+	lockdep_assert_held(&dev->struct_mutex);
+
+	ring = &dev_priv->ring[HAS_BLT(dev) ? BCS : RCS];
+	ctx = i915_gem_context_get(file_priv, DEFAULT_CONTEXT_HANDLE);
+	if (ctx->ppgtt)
+		vm = &ctx->ppgtt->base;
+	else
+		vm = &dev_priv->gtt.base;
+
+	if (i915.enable_execlists && !ctx->engine[ring->id].state) {
+		ret = intel_lr_context_deferred_create(ctx, ring);
+		if (ret)
+			return ret;
+	}
+
+	ringbuf = ctx->engine[ring->id].ringbuf;
+
+	ret = i915_gem_object_pin(obj, vm, PAGE_SIZE, 0);
+	if (ret)
+		return ret;
+
+	if (obj->tiling_mode && INTEL_INFO(dev)->gen <= 3) {
+		ret = i915_gem_object_put_fence(obj);
+		if (ret)
+			goto unpin;
+	}
+
+	ret = i915_gem_exec_flush_object(obj, ring, ctx);
+	if (ret)
+		goto unpin;
+
+	if (i915.enable_execlists) {
+		if (dev_priv->info.gen >= 8) {
+			ret = intel_logical_ring_begin(ringbuf, ctx, 8);
+			if (ret)
+				goto unpin;
+
+			intel_logical_ring_emit(ringbuf, GEN8_COLOR_BLT_CMD |
+							 BLT_WRITE_RGBA |
+							 (7-2));
+			intel_logical_ring_emit(ringbuf, BPP_32 |
+							 ROP_FILL_COPY |
+							 PAGE_SIZE);
+			intel_logical_ring_emit(ringbuf, 0);
+			intel_logical_ring_emit(ringbuf,
+						obj->base.size >> PAGE_SHIFT
+						<< 16 | PAGE_SIZE / 4);
+			intel_logical_ring_emit(ringbuf,
+						i915_gem_obj_offset(obj, vm));
+			intel_logical_ring_emit(ringbuf, 0);
+			intel_logical_ring_emit(ringbuf, 0);
+			intel_logical_ring_emit(ringbuf, MI_NOOP);
+
+			intel_logical_ring_advance(ringbuf);
+		} else {
+			DRM_ERROR("Execlists not supported for gen %d\n",
+				  dev_priv->info.gen);
+			ret = -EINVAL;
+			goto unpin;
+		}
+	} else {
+		if (IS_GEN8(dev)) {
+			ret = intel_ring_begin(ring, 8);
+			if (ret)
+				goto unpin;
+
+			intel_ring_emit(ring, GEN8_COLOR_BLT_CMD |
+					      BLT_WRITE_RGBA | (7-2));
+			intel_ring_emit(ring, BPP_32 |
+					      ROP_FILL_COPY | PAGE_SIZE);
+			intel_ring_emit(ring, 0);
+			intel_ring_emit(ring,
+					obj->base.size >> PAGE_SHIFT << 16 |
+					PAGE_SIZE / 4);
+			intel_ring_emit(ring, i915_gem_obj_offset(obj, vm));
+			intel_ring_emit(ring, 0);
+			intel_ring_emit(ring, 0);
+			intel_ring_emit(ring, MI_NOOP);
+		} else {
+			ret = intel_ring_begin(ring, 6);
+			if (ret)
+				goto unpin;
+
+			intel_ring_emit(ring, COLOR_BLT_CMD |
+					      BLT_WRITE_RGBA);
+			intel_ring_emit(ring, BPP_32 |
+					      ROP_FILL_COPY | PAGE_SIZE);
+			intel_ring_emit(ring,
+					obj->base.size >> PAGE_SHIFT << 16 |
+					PAGE_SIZE);
+			intel_ring_emit(ring, i915_gem_obj_offset(obj, vm));
+			intel_ring_emit(ring, 0);
+			intel_ring_emit(ring, MI_NOOP);
+		}
+
+		__intel_ring_advance(ring);
+	}
+
+	i915_gem_exec_dirty_object(obj, ring, vm);
+
+unpin:
+	i915_gem_obj_to_vma(obj, vm)->pin_count--;
+	return ret;
+}
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index fcb074b..5481638 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -559,7 +559,7 @@ static int execlists_context_queue(struct intel_engine_cs *ring,
 	return 0;
 }
 
-static int logical_ring_invalidate_all_caches(struct intel_ringbuffer *ringbuf,
+int logical_ring_invalidate_all_caches(struct intel_ringbuffer *ringbuf,
 					      struct intel_context *ctx)
 {
 	struct intel_engine_cs *ring = ringbuf->ring;
diff --git a/drivers/gpu/drm/i915/intel_lrc.h b/drivers/gpu/drm/i915/intel_lrc.h
index adb731e4..80a873b 100644
--- a/drivers/gpu/drm/i915/intel_lrc.h
+++ b/drivers/gpu/drm/i915/intel_lrc.h
@@ -42,6 +42,8 @@ int intel_logical_rings_init(struct drm_device *dev);
 
 int logical_ring_flush_all_caches(struct intel_ringbuffer *ringbuf,
 				  struct intel_context *ctx);
+int logical_ring_invalidate_all_caches(struct intel_ringbuffer *ringbuf,
+				       struct intel_context *ctx);
 /**
  * intel_logical_ring_advance() - advance the ringbuffer tail
  * @ringbuf: Ringbuffer to advance.
-- 
1.9.1

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[PATCH 2/4] drm/i915: Support for creating Stolen memory backed objects

[ankitprasad.r.sharma]

From: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>

Extend the drm_i915_gem_create structure to add support for
creating Stolen memory backed objects. Added a new flag through
which user can specify the preference to allocate the object from
stolen memory, which if set, an attempt will be made to allocate
the object from stolen memory subject to the availability of
free space in the stolen region.

testcase: igt/gem_create_stolen

Signed-off-by: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>
---
 drivers/gpu/drm/i915/i915_dma.c |  3 +++
 drivers/gpu/drm/i915/i915_gem.c | 31 +++++++++++++++++++++++++++----
 include/uapi/drm/i915_drm.h     | 15 +++++++++++++++
 3 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index d49ed68..491c91f 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -163,6 +163,9 @@ static int i915_getparam(struct drm_device *dev, void *data,
 		if (!value)
 			return -ENODEV;
 		break;
+	case I915_PARAM_CREATE_VERSION:
+		value = 1;
+		break;
 	default:
 		DRM_DEBUG("Unknown parameter %d\n", param->param);
 		return -EINVAL;
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 84e2a23..81c5381 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -391,7 +391,8 @@ static int
 i915_gem_create(struct drm_file *file,
 		struct drm_device *dev,
 		uint64_t size,
-		uint32_t *handle_p)
+		uint32_t *handle_p,
+		uint32_t flags)
 {
 	struct drm_i915_gem_object *obj;
 	int ret;
@@ -401,8 +402,29 @@ i915_gem_create(struct drm_file *file,
 	if (size == 0)
 		return -EINVAL;
 
+	if (flags & ~(I915_CREATE_PLACEMENT_STOLEN))
+		return -EINVAL;
+
 	/* Allocate the new object */
-	obj = i915_gem_alloc_object(dev, size);
+	if (flags & I915_CREATE_PLACEMENT_STOLEN) {
+		mutex_lock(&dev->struct_mutex);
+		obj = i915_gem_object_create_stolen(dev, size);
+		if (!obj) {
+			mutex_unlock(&dev->struct_mutex);
+			return -ENOMEM;
+		}
+
+		ret = i915_gem_exec_clear_object(obj, file->driver_priv);
+		if (ret) {
+			i915_gem_object_free(obj);
+			mutex_unlock(&dev->struct_mutex);
+			return ret;
+		}
+
+		mutex_unlock(&dev->struct_mutex);
+	} else
+		obj = i915_gem_alloc_object(dev, size);
+
 	if (obj == NULL)
 		return -ENOMEM;
 
@@ -425,7 +447,7 @@ i915_gem_dumb_create(struct drm_file *file,
 	args->pitch = ALIGN(args->width * DIV_ROUND_UP(args->bpp, 8), 64);
 	args->size = args->pitch * args->height;
 	return i915_gem_create(file, dev,
-			       args->size, &args->handle);
+			       args->size, &args->handle, 0);
 }
 
 /**
@@ -438,7 +460,8 @@ i915_gem_create_ioctl(struct drm_device *dev, void *data,
 	struct drm_i915_gem_create *args = data;
 
 	return i915_gem_create(file, dev,
-			       args->size, &args->handle);
+			       args->size, &args->handle,
+			       args->flags);
 }
 
 static inline int
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 8d1be90..ab4f3a9 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -350,6 +350,7 @@ typedef struct drm_i915_irq_wait {
 #define I915_PARAM_REVISION              32
 #define I915_PARAM_SUBSLICE_TOTAL	 33
 #define I915_PARAM_EU_TOTAL		 34
+#define I915_PARAM_CREATE_VERSION	 35
 
 typedef struct drm_i915_getparam {
 	int param;
@@ -445,6 +446,20 @@ struct drm_i915_gem_create {
 	 */
 	__u32 handle;
 	__u32 pad;
+	/**
+	 * Requested flags (currently used for placement
+	 * (which memory domain))
+	 *
+	 * You can request that the object be created from special memory
+	 * rather than regular system pages using this parameter. Such
+	 * irregular objects may have certain restrictions (such as CPU
+	 * access to a stolen object is verboten).
+	 *
+	 * This can be used in the future for other purposes too
+	 * e.g. specifying tiling/caching/madvise
+	 */
+	__u32 flags;
+#define I915_CREATE_PLACEMENT_STOLEN (1<<0) /* Cannot use CPU mmaps or pread/pwrite */
 };
 
 struct drm_i915_gem_pread {
-- 
1.9.1

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[PATCH 3/4] drm/i915: Add support for stealing purgable stolen pages

[ankitprasad.r.sharma]

From: Chris Wilson <chris at chris-wilson.co.uk>

If we run out of stolen memory when trying to allocate an object, see if
we can reap enough purgeable objects to free up enough contiguous free
space for the allocation. This is in principle very much like evicting
objects to free up enough contiguous space in the vma when binding
a new object - and you will be forgiven for thinking that the code looks
very similar.

At the moment, we do not allow userspace to allocate objects in stolen,
so there is neither the memory pressure to trigger stolen eviction nor
any purgeable objects inside the stolen arena. However, this will change
in the near future, and so better management and defragmentation of
stolen memory will become a real issue.

v2: Remember to remove the drm_mm_node.

testcase: igt/gem_create_stolen

Signed-off-by: Chris Wilson <chri@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem_stolen.c | 121 ++++++++++++++++++++++++++++++---
 1 file changed, 110 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c b/drivers/gpu/drm/i915/i915_gem_stolen.c
index f8da716..0a38d71 100644
--- a/drivers/gpu/drm/i915/i915_gem_stolen.c
+++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
@@ -430,18 +430,29 @@ cleanup:
 	return NULL;
 }
 
-struct drm_i915_gem_object *
-i915_gem_object_create_stolen(struct drm_device *dev, u32 size)
+static bool mark_free(struct drm_i915_gem_object *obj, struct list_head *unwind)
+{
+	if (obj->stolen == NULL)
+		return false;
+
+	if (obj->madv != I915_MADV_DONTNEED)
+		return false;
+
+	if (i915_gem_obj_is_pinned(obj))
+		return false;
+
+	list_add(&obj->obj_exec_link, unwind);
+	return drm_mm_scan_add_block(obj->stolen);
+}
+
+static struct drm_mm_node *
+stolen_alloc(struct drm_i915_private *dev_priv, u32 size)
 {
-	struct drm_i915_private *dev_priv = dev->dev_private;
-	struct drm_i915_gem_object *obj;
 	struct drm_mm_node *stolen;
+	struct drm_i915_gem_object *obj;
+	struct list_head unwind, evict;
 	int ret;
 
-	if (!drm_mm_initialized(&dev_priv->mm.stolen))
-		return NULL;
-
-	DRM_DEBUG_KMS("creating stolen object: size=%x\n", size);
 	if (size == 0)
 		return NULL;
 
@@ -451,11 +462,99 @@ i915_gem_object_create_stolen(struct drm_device *dev, u32 size)
 
 	ret = drm_mm_insert_node(&dev_priv->mm.stolen, stolen, size,
 				 4096, DRM_MM_SEARCH_DEFAULT);
-	if (ret) {
-		kfree(stolen);
-		return NULL;
+	if (ret == 0)
+		return stolen;
+
+	/* No more stolen memory available, or too fragmented.
+	 * Try evicting purgeable objects and search again.
+	 */
+
+	drm_mm_init_scan(&dev_priv->mm.stolen, size, 4096, 0);
+	INIT_LIST_HEAD(&unwind);
+
+	list_for_each_entry(obj, &dev_priv->mm.unbound_list, global_list)
+		if (mark_free(obj, &unwind))
+			goto found;
+
+	list_for_each_entry(obj, &dev_priv->mm.bound_list, global_list)
+		if (mark_free(obj, &unwind))
+			goto found;
+
+found:
+	INIT_LIST_HEAD(&evict);
+	while (!list_empty(&unwind)) {
+		obj = list_first_entry(&unwind,
+				       struct drm_i915_gem_object,
+				       obj_exec_link);
+		list_del_init(&obj->obj_exec_link);
+
+		if (drm_mm_scan_remove_block(obj->stolen)) {
+			list_add(&obj->obj_exec_link, &evict);
+			drm_gem_object_reference(&obj->base);
+		}
 	}
 
+	ret = 0;
+	while (!list_empty(&evict)) {
+		obj = list_first_entry(&evict,
+				       struct drm_i915_gem_object,
+				       obj_exec_link);
+		list_del_init(&obj->obj_exec_link);
+
+		if (ret == 0) {
+			struct i915_vma *vma, *vma_next;
+
+			list_for_each_entry_safe(vma, vma_next,
+						 &obj->vma_list,
+						 vma_link)
+				if (i915_vma_unbind(vma))
+					break;
+
+			/* Stolen pins its pages to prevent the
+			 * normal shrinker from processing stolen
+			 * objects.
+			 */
+			i915_gem_object_unpin_pages(obj);
+
+			ret = i915_gem_object_put_pages(obj);
+			if (ret == 0) {
+				i915_gem_object_release_stolen(obj);
+				obj->madv = __I915_MADV_PURGED;
+			} else
+				i915_gem_object_pin_pages(obj);
+		}
+
+		drm_gem_object_unreference(&obj->base);
+	}
+
+	if (ret == 0)
+		ret = drm_mm_insert_node(&dev_priv->mm.stolen, stolen, size,
+					 4096, DRM_MM_SEARCH_DEFAULT);
+	if (ret == 0)
+		return stolen;
+
+	kfree(stolen);
+	return NULL;
+}
+
+struct drm_i915_gem_object *
+i915_gem_object_create_stolen(struct drm_device *dev, u32 size)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct drm_i915_gem_object *obj;
+	struct drm_mm_node *stolen;
+
+	lockdep_assert_held(&dev->struct_mutex);
+
+	if (!drm_mm_initialized(&dev_priv->mm.stolen))
+		return NULL;
+
+	DRM_DEBUG_KMS("creating stolen object: size=%x\n", size);
+
+	stolen = stolen_alloc(dev_priv, size);
+	if (stolen == NULL)
+		return NULL;
+
 	obj = _i915_gem_object_create_stolen(dev, stolen);
 	if (obj)
 		return obj;
-- 
1.9.1

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[PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem backed objects

[ankitprasad.r.sharma]

From: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>

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 prime objects as well as stolen memory backed objects
but for userptr objects it is still forbidden.

v2: drop locks around slow_user_access, prefault the pages before
access (Chris)

testcase: igt/gem_create_stolen

Signed-off-by: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>
---
 drivers/gpu/drm/i915/i915_gem.c | 137 +++++++++++++++++++++++++++++++++++-----
 1 file changed, 120 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 81c5381..fe14ddc 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -631,6 +631,102 @@ shmem_pread_slow(struct page *page, int shmem_page_offset, int page_length,
 	return ret ? - EFAULT : 0;
 }
 
+static inline int
+slow_user_access(struct io_mapping *mapping,
+		 loff_t page_base, int page_offset,
+		 char __user *user_data,
+		 int length, bool write)
+{
+	void __iomem *vaddr_inatomic;
+	void *vaddr;
+	unsigned long 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 (write)
+		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_pread_pwrite(struct drm_device *dev,
+			  struct drm_i915_gem_object *obj, uint64_t size,
+			  uint64_t data_offset, uint64_t data_ptr, bool write)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	char __user *user_data;
+	ssize_t remain;
+	loff_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, write);
+	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;
+
+	if (write)
+		intel_fb_obj_invalidate(obj, NULL, ORIGIN_GTT);
+
+	mutex_unlock(&dev->struct_mutex);
+	if (!write && likely(!i915.prefault_disable))
+		ret = fault_in_multipages_writeable(user_data, remain);
+
+	while (remain > 0) {
+		/* Operation in this page
+		 *
+		 * page_base = page offset within aperture
+		 * page_offset = offset within page
+		 * page_length = bytes to copy for this page
+		 */
+		page_base = offset & PAGE_MASK;
+		page_offset = offset_in_page(offset);
+		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, write);
+
+		if (ret) {
+			ret = -EINVAL;
+			break;
+		}
+
+		remain -= page_length;
+		user_data += page_length;
+		offset += page_length;
+	}
+
+	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,
@@ -754,17 +850,19 @@ 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) {
+		if (obj->tiling_mode == I915_TILING_NONE)
+			ret = i915_gem_gtt_pread_pwrite(dev, obj, args->size,
+							args->offset,
+							args->data_ptr,
+							false);
+		else
+			ret = -EINVAL;
+	} else
+		ret = i915_gem_shmem_pread(dev, obj, args, file);
 
 out:
 	drm_gem_object_unreference(&obj->base);
@@ -1107,17 +1205,22 @@ i915_gem_pwrite_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_pwrite(obj, args->offset, args->size);
 
 	ret = -EFAULT;
+
+	/* pwrite for non shmem backed objects */
+	if (!obj->base.filp) {
+		if (obj->tiling_mode == I915_TILING_NONE)
+			ret = i915_gem_gtt_pread_pwrite(dev, obj, args->size,
+							args->offset,
+							args->data_ptr,
+							true);
+		else
+			ret = -EINVAL;
+
+		goto out;
+	}
 	/* 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.
-- 
1.9.1

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Re: [PATCH v3 0/4] Support for creating/using Stolen memory backed objects

[Jesse Barnes]

[Cc'ing Chris, not sure if he saw the updated version to give his r-b]


On 05/06/2015 03:15 AM, ankitprasad.r.sharma@intel.com wrote:
> From: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>
> 
> This patch series adds support for creating/using Stolen memory backed
> objects.
> 
> Despite being a unified memory architecture (UMA) some bits of memory
> are more equal than others. In particular we have the thorny issue of
> stolen memory, memory stolen from the system by the BIOS and reserved
> for igfx use. Stolen memory is required for some functions of the GPU
> and display engine, but in general it goes wasted. Whilst we cannot
> return it back to the system, we need to find some other method for
> utilising it. As we do not support direct access to the physical address
> in the stolen region, it behaves like a different class of memory,
> closer in kin to local GPU memory. This strongly suggests that we need a
> placement model like TTM if we are to fully utilize these discrete
> chunks of differing memory.
> 
> To add support for creating Stolen memory backed objects, we extend the
> drm_i915_gem_create structure, by adding a new flag through which user
> can specify the preference to allocate the object from stolen memory,
> which if set, an attempt will be made to allocate the object from stolen
> memory subject to the availability of free space in the stolen region.
> 
> This patch series adds support for clearing buffer objects via blitter
> engines. This is particularly useful for clearing out the memory from
> stolen region, but can also be used for other shmem allocated objects.
> Also adding support for stealing purgable stolen pages, if we run out
> of stolen memory when trying to allocate an object.
> 
> v2: Added support for read/write from/to objects not backed by
> shmem using the pread/pwrite interface.
> Also extended the current get_aperture ioctl to retrieve the
> total and available size of the stolen region
> 
> v3: Removed the extended get_aperture ioctl patch 5 (to be submitted as
> part of other patch series), addressed comments by Chris about pread/pwrite
> for non shmem backed objects
> 
> This can be verified using IGT tests: igt/gem_create_stolen
> 
> Ankitprasad Sharma (3):
>   drm/i915: Clearing buffer objects via blitter engine
>   drm/i915: Support for creating Stolen memory backed objects
>   drm/i915: Support for pread/pwrite from/to non shmem backed objects
> 
> Chris Wilson (1):
>   drm/i915: Add support for stealing purgable stolen pages
> 
>  drivers/gpu/drm/i915/Makefile          |   1 +
>  drivers/gpu/drm/i915/i915_dma.c        |   3 +
>  drivers/gpu/drm/i915/i915_drv.h        |   4 +
>  drivers/gpu/drm/i915/i915_gem.c        | 168 ++++++++++++++++++++++++----
>  drivers/gpu/drm/i915/i915_gem_exec.c   | 197 +++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/i915_gem_stolen.c | 121 ++++++++++++++++++--
>  drivers/gpu/drm/i915/intel_lrc.c       |   2 +-
>  drivers/gpu/drm/i915/intel_lrc.h       |   2 +
>  include/uapi/drm/i915_drm.h            |  15 +++
>  9 files changed, 480 insertions(+), 33 deletions(-)
>  create mode 100644 drivers/gpu/drm/i915/i915_gem_exec.c
> 

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Re: [PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem backed objects

[Ankitprasad Sharma]

On Tue, 2015-09-15 at 10:54 +0100, Chris Wilson wrote:
> On Tue, Sep 15, 2015 at 02:03:27PM +0530, ankitprasad.r.sharma@intel.com wrote:
> > @@ -1090,17 +1184,17 @@ i915_gem_pwrite_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_pwrite(obj, args->offset, args->size);
> >  
> >  	ret = -EFAULT;
> > +
> > +	/* pwrite for non shmem backed objects */
> > +	if (!obj->base.filp) {
> > +		ret = i915_gem_gtt_pread_pwrite(dev, obj, args->size,
> > +						args->offset, args->data_ptr,
> > +						true);
> > +		goto out;
> > +	}
> 
> There already exists a GTT write path, along with a more correct
> description of its limitations.

Then it would look something like this, making i915_gem_gtt_pwrite_fast
to handle pagefaults for non-shmem backed objects

@@ -831,10 +925,16 @@ i915_gem_gtt_pwrite_fast(struct drm_device *dev,
                 * retry in the slow path.
                 */
-         if (fast_user_write(dev_priv->gtt.mappable, page_base,
+            if (obj->base.filp &&
+                 fast_user_write(dev_priv->gtt.mappable, page_base,
                                 page_offset, user_data, page_length)) {
                        ret = -EFAULT;
                        goto out_flush;
+            } else if (slow_user_access(dev_priv->gtt.mappable,
+                                        page_base, page_offset,
+                                       user_data, page_length, true)) {
+                       ret = -EFAULT;
+                       goto out_flush;
             }
 
Thanks
-Ankit


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Re: [PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem backed objects

[Chris Wilson]

On Fri, Jul 31, 2015 at 06:46:20PM +0530, Goel, Akash wrote:
> Since the suggestion is to reuse the gtt_pwrite_fast function only
> for non-shmem backed objects, can we also relax the Tiling
> constraint here, apart from removing the PIN_NONBLOCK flag. As
> anyways there is a put_fence already being done in gtt_pwrite_fast
> function.

The tiling restraint is due to a hardware limitation (the effect of
swizzling), you cannot simply drop it.
-Chris

-- 
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Re: [PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem backed objects

[Chris Wilson]

On Tue, Sep 15, 2015 at 02:03:27PM +0530, ankitprasad.r.sharma@intel.com wrote:
> @@ -1090,17 +1184,17 @@ i915_gem_pwrite_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_pwrite(obj, args->offset, args->size);
>  
>  	ret = -EFAULT;
> +
> +	/* pwrite for non shmem backed objects */
> +	if (!obj->base.filp) {
> +		ret = i915_gem_gtt_pread_pwrite(dev, obj, args->size,
> +						args->offset, args->data_ptr,
> +						true);
> +		goto out;
> +	}

There already exists a GTT write path, along with a more correct
description of its limitations.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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[PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem backed objects

[ankitprasad.r.sharma]

From: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>

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 prime objects as well as stolen memory backed objects
but for userptr objects it is still forbidden.

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)

Testcase: igt/gem_stolen

Signed-off-by: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>
---
 drivers/gpu/drm/i915/i915_gem.c | 128 ++++++++++++++++++++++++++++++++++------
 1 file changed, 111 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 85025b1..2df37ac 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -614,6 +614,102 @@ 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_pread_pwrite(struct drm_device *dev,
+			  struct drm_i915_gem_object *obj, uint64_t size,
+			  uint64_t data_offset, uint64_t data_ptr, bool pwrite)
+{
+	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, pwrite);
+	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;
+
+	if (pwrite)
+		intel_fb_obj_invalidate(obj, ORIGIN_GTT);
+
+	mutex_unlock(&dev->struct_mutex);
+	if (!pwrite && 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, pwrite);
+
+		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 +833,15 @@ 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)
+		ret = i915_gem_gtt_pread_pwrite(dev, obj, args->size,
+						args->offset, args->data_ptr,
+						false);
+	else
+		ret = i915_gem_shmem_pread(dev, obj, args, file);
 
 out:
 	drm_gem_object_unreference(&obj->base);
@@ -1090,17 +1184,17 @@ i915_gem_pwrite_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_pwrite(obj, args->offset, args->size);
 
 	ret = -EFAULT;
+
+	/* pwrite for non shmem backed objects */
+	if (!obj->base.filp) {
+		ret = i915_gem_gtt_pread_pwrite(dev, obj, args->size,
+						args->offset, args->data_ptr,
+						true);
+		goto out;
+	}
 	/* 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.
-- 
1.9.1

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Re: [PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem backed objects

[Ankitprasad Sharma]

On Fri, 2015-07-31 at 18:46 +0530, Goel, Akash wrote:
> 
> On 7/22/2015 8:09 PM, Chris Wilson wrote:
> > On Wed, Jul 22, 2015 at 07:21:49PM +0530, ankitprasad.r.sharma@intel.com wrote:
> >>   static int
> >>   i915_gem_shmem_pread(struct drm_device *dev,
> >>   		     struct drm_i915_gem_object *obj,
> >> @@ -754,17 +850,20 @@ 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) {
> >> +		if (obj->tiling_mode == I915_TILING_NONE)
> >
> > pread/pwrite is defined as a cpu linear, the restriction upon tiling is
> > a simplification of handling swizzling.
> >
> >> +			ret = i915_gem_gtt_pread_pwrite(dev, obj, args->size,
> >> +							args->offset,
> >> +							args->data_ptr,
> >> +							false);
> >> +		else
> >> +			ret = -EINVAL;
> >> +	} else {
> >> +		ret = i915_gem_shmem_pread(dev, obj, args, file);
> >> +	}
> >>
> >>   out:
> >>   	drm_gem_object_unreference(&obj->base);
> >> @@ -1105,17 +1204,22 @@ i915_gem_pwrite_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_pwrite(obj, args->offset, args->size);
> >>
> >>   	ret = -EFAULT;
> >> +
> >> +	/* pwrite for non shmem backed objects */
> >> +	if (!obj->base.filp) {
> >> +		if (obj->tiling_mode == I915_TILING_NONE)
> >> +			ret = i915_gem_gtt_pread_pwrite(dev, obj, args->size,
> >> +							args->offset,
> >> +							args->data_ptr,
> >> +							true);
> >> +		else
> >> +			ret = -EINVAL;
> >> +
> >> +		goto out;
> >
> > The fast pwrite code always works for obj->base.filp == NULL. To easily
> > make it generic and handle the cases where we cannot fallback to shem,
> > undo the PIN_NONBLOCK.
> >
> > Then you just want something like
> > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> > index d3016f37cd4d..f2284a27dd6d 100644
> > --- a/drivers/gpu/drm/i915/i915_gem.c
> > +++ b/drivers/gpu/drm/i915/i915_gem.c
> > @@ -1114,8 +1114,9 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
> >           * perspective, requiring manual detiling by the client.
> >           */
> >          if (obj->tiling_mode == I915_TILING_NONE &&
> 
> Since the suggestion is to reuse the gtt_pwrite_fast function only for 
> non-shmem backed objects, can we also relax the Tiling constraint here, 
> apart from removing the PIN_NONBLOCK flag. As anyways there is a 
> put_fence already being done in gtt_pwrite_fast function.
> 
> Also currently the gtt_pwrite_fast function is non-tolerant to faults, 
> incurred while accessing the User space buffer, so can that also be 
> relaxed (at least for the non-shmem backed objects) ??

Even if we reuse the gtt_pwrite_fast we will have to handle page-faults
for non-shmem backed objects, that will contradict the purpose of
gtt_pwrite_fast. The gtt_pread_pwrite will still be around for pread
purpose.

Also, I think it should be ok to relax the tiling constraint as well, as
we put_fence everytime we try to pread/pwrite from/to a non-shmem-backed
object here.

Thanks,
Ankit

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Re: [PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem backed objects

[Goel, Akash]

On 7/22/2015 8:09 PM, Chris Wilson wrote:
> On Wed, Jul 22, 2015 at 07:21:49PM +0530, ankitprasad.r.sharma@intel.com wrote:
>>   static int
>>   i915_gem_shmem_pread(struct drm_device *dev,
>>   		     struct drm_i915_gem_object *obj,
>> @@ -754,17 +850,20 @@ 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) {
>> +		if (obj->tiling_mode == I915_TILING_NONE)
>
> pread/pwrite is defined as a cpu linear, the restriction upon tiling is
> a simplification of handling swizzling.
>
>> +			ret = i915_gem_gtt_pread_pwrite(dev, obj, args->size,
>> +							args->offset,
>> +							args->data_ptr,
>> +							false);
>> +		else
>> +			ret = -EINVAL;
>> +	} else {
>> +		ret = i915_gem_shmem_pread(dev, obj, args, file);
>> +	}
>>
>>   out:
>>   	drm_gem_object_unreference(&obj->base);
>> @@ -1105,17 +1204,22 @@ i915_gem_pwrite_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_pwrite(obj, args->offset, args->size);
>>
>>   	ret = -EFAULT;
>> +
>> +	/* pwrite for non shmem backed objects */
>> +	if (!obj->base.filp) {
>> +		if (obj->tiling_mode == I915_TILING_NONE)
>> +			ret = i915_gem_gtt_pread_pwrite(dev, obj, args->size,
>> +							args->offset,
>> +							args->data_ptr,
>> +							true);
>> +		else
>> +			ret = -EINVAL;
>> +
>> +		goto out;
>
> The fast pwrite code always works for obj->base.filp == NULL. To easily
> make it generic and handle the cases where we cannot fallback to shem,
> undo the PIN_NONBLOCK.
>
> Then you just want something like
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index d3016f37cd4d..f2284a27dd6d 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1114,8 +1114,9 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
>           * perspective, requiring manual detiling by the client.
>           */
>          if (obj->tiling_mode == I915_TILING_NONE &&

Since the suggestion is to reuse the gtt_pwrite_fast function only for 
non-shmem backed objects, can we also relax the Tiling constraint here, 
apart from removing the PIN_NONBLOCK flag. As anyways there is a 
put_fence already being done in gtt_pwrite_fast function.

Also currently the gtt_pwrite_fast function is non-tolerant to faults, 
incurred while accessing the User space buffer, so can that also be 
relaxed (at least for the non-shmem backed objects) ??

Best regards
Akash

> -           obj->base.write_domain != I915_GEM_DOMAIN_CPU &&
> -           cpu_write_needs_clflush(obj)) {
> +           (obj->base.filp == NULL ||
> +            (obj->base.write_domain != I915_GEM_DOMAIN_CPU &&
> +             cpu_write_needs_clflush(obj)))) {
>                  ret = i915_gem_gtt_pwrite_fast(dev_priv, obj, args, file);
>                  /* Note that the gtt paths might fail with non-page-backed user
>                   * pointers (e.g. gtt mappings when moving data between
> @@ -1125,7 +1126,7 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
>          if (ret == -EFAULT || ret == -ENOSPC) {
>                  if (obj->phys_handle)
>                          ret = i915_gem_phys_pwrite(obj, args, file);
> -               else
> +               else if (obj->filp)
>                          ret = i915_gem_shmem_pwrite(dev, obj, args, file);
>          }
>
>
> to enable pwrite access to stolen.
> -Chris
>
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Re: [PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem backed objects

[Tvrtko Ursulin]

On 07/22/2015 05:05 PM, Daniel Vetter wrote:
> On Wed, Jul 22, 2015 at 04:46:00PM +0100, Tvrtko Ursulin wrote:
>> But also, why it is even necessary to drop the mutex here?
>
> Locking inversion with our own pagefault handler. Happens since at least
> mesa can return gtt mmaps to gl clients, which can then in turn try to
> upload that with pwrite somewhere else. Also userspace could be just plain
> nasty and try to deadlock the kernel ;-)

Yeah blame userspace. ;D

> Dropping the struct_mutex is SOP for the copy_from/to_user slowpath.

I suspected something like that but did not feel like thinking too much. 
:) When encountering unusual things like dropping and re-acquiring locks 
I expect to see comments explaining it.

Regards,

Tvrtko
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Re: [PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem backed objects

[Daniel Vetter]

On Wed, Jul 22, 2015 at 04:46:00PM +0100, Tvrtko Ursulin wrote:
> But also, why it is even necessary to drop the mutex here?

Locking inversion with our own pagefault handler. Happens since at least
mesa can return gtt mmaps to gl clients, which can then in turn try to
upload that with pwrite somewhere else. Also userspace could be just plain
nasty and try to deadlock the kernel ;-)

Dropping the struct_mutex is SOP for the copy_from/to_user slowpath.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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Re: [PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem backed objects

[Tvrtko Ursulin]

Hi,

On 07/22/2015 02:51 PM, ankitprasad.r.sharma@intel.com wrote:
> From: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>
>
> 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 prime objects as well as stolen memory backed objects
> but for userptr objects it is still forbidden.
>
> 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)
>
> Testcase: igt/gem_stolen
>
> Signed-off-by: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>
> ---
>   drivers/gpu/drm/i915/i915_gem.c | 138 +++++++++++++++++++++++++++++++++++-----
>   1 file changed, 121 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 9e7e182..4321178 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -631,6 +631,102 @@ 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_pread_pwrite(struct drm_device *dev,
> +			  struct drm_i915_gem_object *obj, uint64_t size,
> +			  uint64_t data_offset, uint64_t data_ptr, bool pwrite)
> +{
> +	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, pwrite);
> +	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;
> +
> +	if (pwrite)
> +		intel_fb_obj_invalidate(obj, ORIGIN_GTT);
> +
> +	mutex_unlock(&dev->struct_mutex);
> +	if (!pwrite && 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, pwrite);
> +
> +		if (ret) {
> +			ret = -EFAULT;
> +			break;
> +		}
> +
> +		remain -= page_length;
> +		user_data += page_length;
> +		page_base += page_length;
> +		page_offset = 0;
> +	}
> +
> +	mutex_lock(&dev->struct_mutex);

My objection here was that we are re-acquiring the mutex in 
non-interruptible mode, while the caller had it interruptible. It am not 
100% what the conclusion back then was?

But also, why it is even necessary to drop the mutex here?

Regards,

Tvrtko
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Re: [PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem backed objects

[Chris Wilson]

On Wed, Jul 22, 2015 at 07:21:49PM +0530, ankitprasad.r.sharma@intel.com wrote:
>  static int
>  i915_gem_shmem_pread(struct drm_device *dev,
>  		     struct drm_i915_gem_object *obj,
> @@ -754,17 +850,20 @@ 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) {
> +		if (obj->tiling_mode == I915_TILING_NONE)

pread/pwrite is defined as a cpu linear, the restriction upon tiling is
a simplification of handling swizzling.

> +			ret = i915_gem_gtt_pread_pwrite(dev, obj, args->size,
> +							args->offset,
> +							args->data_ptr,
> +							false);
> +		else
> +			ret = -EINVAL;
> +	} else {
> +		ret = i915_gem_shmem_pread(dev, obj, args, file);
> +	}
>  
>  out:
>  	drm_gem_object_unreference(&obj->base);
> @@ -1105,17 +1204,22 @@ i915_gem_pwrite_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_pwrite(obj, args->offset, args->size);
>  
>  	ret = -EFAULT;
> +
> +	/* pwrite for non shmem backed objects */
> +	if (!obj->base.filp) {
> +		if (obj->tiling_mode == I915_TILING_NONE)
> +			ret = i915_gem_gtt_pread_pwrite(dev, obj, args->size,
> +							args->offset,
> +							args->data_ptr,
> +							true);
> +		else
> +			ret = -EINVAL;
> +
> +		goto out;

The fast pwrite code always works for obj->base.filp == NULL. To easily
make it generic and handle the cases where we cannot fallback to shem,
undo the PIN_NONBLOCK.

Then you just want something like
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index d3016f37cd4d..f2284a27dd6d 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1114,8 +1114,9 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
         * perspective, requiring manual detiling by the client.
         */
        if (obj->tiling_mode == I915_TILING_NONE &&
-           obj->base.write_domain != I915_GEM_DOMAIN_CPU &&
-           cpu_write_needs_clflush(obj)) {
+           (obj->base.filp == NULL ||
+            (obj->base.write_domain != I915_GEM_DOMAIN_CPU &&
+             cpu_write_needs_clflush(obj)))) {
                ret = i915_gem_gtt_pwrite_fast(dev_priv, obj, args, file);
                /* Note that the gtt paths might fail with non-page-backed user
                 * pointers (e.g. gtt mappings when moving data between
@@ -1125,7 +1126,7 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
        if (ret == -EFAULT || ret == -ENOSPC) {
                if (obj->phys_handle)
                        ret = i915_gem_phys_pwrite(obj, args, file);
-               else
+               else if (obj->filp)
                        ret = i915_gem_shmem_pwrite(dev, obj, args, file);
        }
 

to enable pwrite access to stolen.
-Chris

-- 
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[PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem backed objects

[ankitprasad.r.sharma]

From: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>

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 prime objects as well as stolen memory backed objects
but for userptr objects it is still forbidden.

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)

Testcase: igt/gem_stolen

Signed-off-by: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>
---
 drivers/gpu/drm/i915/i915_gem.c | 138 +++++++++++++++++++++++++++++++++++-----
 1 file changed, 121 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 9e7e182..4321178 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -631,6 +631,102 @@ 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_pread_pwrite(struct drm_device *dev,
+			  struct drm_i915_gem_object *obj, uint64_t size,
+			  uint64_t data_offset, uint64_t data_ptr, bool pwrite)
+{
+	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, pwrite);
+	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;
+
+	if (pwrite)
+		intel_fb_obj_invalidate(obj, ORIGIN_GTT);
+
+	mutex_unlock(&dev->struct_mutex);
+	if (!pwrite && 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, pwrite);
+
+		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,
@@ -754,17 +850,20 @@ 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) {
+		if (obj->tiling_mode == I915_TILING_NONE)
+			ret = i915_gem_gtt_pread_pwrite(dev, obj, args->size,
+							args->offset,
+							args->data_ptr,
+							false);
+		else
+			ret = -EINVAL;
+	} else {
+		ret = i915_gem_shmem_pread(dev, obj, args, file);
+	}
 
 out:
 	drm_gem_object_unreference(&obj->base);
@@ -1105,17 +1204,22 @@ i915_gem_pwrite_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_pwrite(obj, args->offset, args->size);
 
 	ret = -EFAULT;
+
+	/* pwrite for non shmem backed objects */
+	if (!obj->base.filp) {
+		if (obj->tiling_mode == I915_TILING_NONE)
+			ret = i915_gem_gtt_pread_pwrite(dev, obj, args->size,
+							args->offset,
+							args->data_ptr,
+							true);
+		else
+			ret = -EINVAL;
+
+		goto out;
+	}
 	/* 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.
-- 
1.9.1

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Re: [PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem backed objects

[shuang.he]

Tested-By: Intel Graphics QA PRTS (Patch Regression Test System Contact: shuang.he@intel.com)
Task id: 6697
-------------------------------------Summary-------------------------------------
Platform          Delta          drm-intel-nightly          Series Applied
ILK                                  302/302              302/302
SNB                                  312/316              312/316
IVB                                  343/343              343/343
BYT                 -1              287/287              286/287
HSW                                  380/380              380/380
-------------------------------------Detailed-------------------------------------
Platform  Test                                drm-intel-nightly          Series Applied
*BYT  igt@gem_tiled_partial_pwrite_pread@reads      PASS(1)      FAIL(1)
Note: You need to pay more attention to line start with '*'
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Re: [PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem backed objects

[Chris Wilson]

On Thu, Jul 02, 2015 at 12:27:42PM +0100, Tvrtko Ursulin wrote:
> 
> On 07/02/2015 12:00 PM, Chris Wilson wrote:
> >>>+		/* 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, write);
> >>>+
> >>>+		if (ret) {
> >>>+			ret = -EINVAL;
> >
> >Would be better to return the right errno from slow_user_access or if it
> >is a bool, treat is a bool!
> 
> It returns a number of unwritten bytes.
> 
> Actually just spotted the return type for slow_user_access is also
> wrong, it is an int, to which it implicitly casts an unsigned long.

Ugh, our convention for those has to been to do the unwritten check in
the subroutine and convert it back to the errno. Saves all the guessing
about the failure mode in the caller.
 
> And it is customary to return -EFAULT on rather than -EINVAL so I
> suggest changing that as well.

Yup.
 
> >>>+			break;
> >>>+		}
> >>>+
> >>>+		remain -= page_length;
> >>>+		user_data += page_length;
> >>>+		offset += page_length;
> >>>+	}
> >>>+
> >>>+	mutex_lock(&dev->struct_mutex);
> >>
> >>Caller had it interruptible.
> >
> >On second access, it is preferrable not to risk interruption -
> >especially when catching up with state to return to userspace.
> 
> 
> Second access is only in pwrite case and more so, it makes no sense
> to make such decisions on behalf of the caller. If it is a real
> concern, caller should do it.

That's odd. We must have taken it on both pwrite/pread paths to have
prepared the object for reading/writing. We can only dropped it under
difficult circumstances (lots of dancing required if we do to make sure
that the object hasn't been modified in the meantime).
 
> Yes I see that there is a problem where this helper doesn't know
> what type of mutex caller had, but, it is still bad imho and could
> be fixed in a different way.

Smells fishy indeed.
-Chris

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Re: [PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem backed objects

[Tvrtko Ursulin]

On 07/02/2015 12:00 PM, Chris Wilson wrote:
>>> +		/* 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, write);
>>> +
>>> +		if (ret) {
>>> +			ret = -EINVAL;
>
> Would be better to return the right errno from slow_user_access or if it
> is a bool, treat is a bool!

It returns a number of unwritten bytes.

Actually just spotted the return type for slow_user_access is also 
wrong, it is an int, to which it implicitly casts an unsigned long.

And it is customary to return -EFAULT on rather than -EINVAL so I 
suggest changing that as well.

>>> +			break;
>>> +		}
>>> +
>>> +		remain -= page_length;
>>> +		user_data += page_length;
>>> +		offset += page_length;
>>> +	}
>>> +
>>> +	mutex_lock(&dev->struct_mutex);
>>
>> Caller had it interruptible.
>
> On second access, it is preferrable not to risk interruption -
> especially when catching up with state to return to userspace.


Second access is only in pwrite case and more so, it makes no sense to 
make such decisions on behalf of the caller. If it is a real concern, 
caller should do it.

Yes I see that there is a problem where this helper doesn't know what 
type of mutex caller had, but, it is still bad imho and could be fixed 
in a different way.

Regards,

Tvrtko
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Re: [PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem backed objects

[Chris Wilson]

On Thu, Jul 02, 2015 at 11:42:44AM +0100, Tvrtko Ursulin wrote:
> I am not super familiar with low level mapping business. But it
> looks correct to me. Just one question would be if there are any
> downsides to WC mapping? If in the read case it would be any
> advantage not to ask for WC?

Read-side WC behaves as UC. It's bad, but since we have no other
coherent access we have no choice. We rely on userspace not to do this,
and our powers of persuasion that copying to a coherent buffer first
using the GPU and then using the CPU for readback is about 8x faster
(incl. the sync overhead) then having to use UC.
 
> >+static int
> >+i915_gem_gtt_pread_pwrite(struct drm_device *dev,
> >+			  struct drm_i915_gem_object *obj, uint64_t size,
> >+			  uint64_t data_offset, uint64_t data_ptr, bool write)
> >+{
> >+	struct drm_i915_private *dev_priv = dev->dev_private;
> >+	char __user *user_data;
> >+	ssize_t remain;
> >+	loff_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, write);
> >+	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;
> 
> Strictly speaking uint64_t can overflow ssize_t, compiler does not
> care in this case?

compiler is too quiet at times. Killing ssize_t and even loff_t here
makes sense.

> >+	offset = i915_gem_obj_ggtt_offset(obj) + data_offset;
> >+
> >+	if (write)
> >+		intel_fb_obj_invalidate(obj, ORIGIN_GTT);

Smells wrong, better off combining the invalidate with the right flags
in the caller.

> >+	mutex_unlock(&dev->struct_mutex);
> >+	if (!write && likely(!i915.prefault_disable))
> >+		ret = fault_in_multipages_writeable(user_data, remain);
> 
> A bit confusing read/write inversion. :) But correct. Just wondering
> if it would make sense to invert the boolean at least in
> slow_user_access. Or in fact just call it pwrite instead of write to
> reflect pwrite == true is _reading_ from user memory.
> 
> >+	while (remain > 0) {
> >+		/* Operation in this page
> >+		 *
> >+		 * page_base = page offset within aperture
> >+		 * page_offset = offset within page
> >+		 * page_length = bytes to copy for this page
> >+		 */
> >+		page_base = offset & PAGE_MASK;
> >+		page_offset = offset_in_page(offset);
> >+		page_length = remain;
> >+		if ((page_offset + remain) > PAGE_SIZE)
> >+			page_length = PAGE_SIZE - page_offset;
> 
> It would save some arithmetics and branching to pull out the first
> potentially unaligned copy out of the loop and then page_offset
> would be zero for 2nd page onwards.

Honestly, keeping the loop simple is preferable :) What I do locally if

page_offset = offset_in_page();
offset &= PAGE_MASK;
while (remain > 0) {
	len = min(remain, PAGE_SIZE - page_offset);
	....
	user_data += len;
	remain -= len;
	offset += PAGE_SIZE;
	page_offset = 0;
}

> 
> >+		/* 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, write);
> >+
> >+		if (ret) {
> >+			ret = -EINVAL;

Would be better to return the right errno from slow_user_access or if it
is a bool, treat is a bool!

> >+			break;
> >+		}
> >+
> >+		remain -= page_length;
> >+		user_data += page_length;
> >+		offset += page_length;
> >+	}
> >+
> >+	mutex_lock(&dev->struct_mutex);
> 
> Caller had it interruptible.

On second access, it is preferrable not to risk interruption -
especially when catching up with state to return to userspace.
-Chris

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Re: [PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem backed objects

[Tvrtko Ursulin]

On 07/01/2015 10:25 AM, ankitprasad.r.sharma@intel.com wrote:
> From: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>
>
> 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 prime objects as well as stolen memory backed objects
> but for userptr objects it is still forbidden.
>
> v2: drop locks around slow_user_access, prefault the pages before
> access (Chris)
>
> v3: Rebased to the latest drm-intel-nightly (Ankit)
>
> testcase: igt/gem_stolen
 >
> Signed-off-by: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>
> ---
>   drivers/gpu/drm/i915/i915_gem.c | 137 +++++++++++++++++++++++++++++++++++-----
>   1 file changed, 120 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 4acf331..4be6eb4 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -629,6 +629,102 @@ shmem_pread_slow(struct page *page, int shmem_page_offset, int page_length,
>   	return ret ? - EFAULT : 0;
>   }
>
> +static inline int
> +slow_user_access(struct io_mapping *mapping,
> +		 loff_t page_base, int page_offset,
> +		 char __user *user_data,
> +		 int length, bool write)
> +{
> +	void __iomem *vaddr_inatomic;
> +	void *vaddr;
> +	unsigned long 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 (write)
> +		unwritten = __copy_from_user(vaddr, user_data, length);
> +	else
> +		unwritten = __copy_to_user(user_data, vaddr, length);
> +
> +	io_mapping_unmap(vaddr_inatomic);
> +	return unwritten;
> +}

I am not super familiar with low level mapping business. But it looks 
correct to me. Just one question would be if there are any downsides to 
WC mapping? If in the read case it would be any advantage not to ask for WC?

> +static int
> +i915_gem_gtt_pread_pwrite(struct drm_device *dev,
> +			  struct drm_i915_gem_object *obj, uint64_t size,
> +			  uint64_t data_offset, uint64_t data_ptr, bool write)
> +{
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +	char __user *user_data;
> +	ssize_t remain;
> +	loff_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, write);
> +	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;

Strictly speaking uint64_t can overflow ssize_t, compiler does not care 
in this case?

> +
> +	offset = i915_gem_obj_ggtt_offset(obj) + data_offset;
> +
> +	if (write)
> +		intel_fb_obj_invalidate(obj, ORIGIN_GTT);
> +
> +	mutex_unlock(&dev->struct_mutex);
> +	if (!write && likely(!i915.prefault_disable))
> +		ret = fault_in_multipages_writeable(user_data, remain);

A bit confusing read/write inversion. :) But correct. Just wondering if 
it would make sense to invert the boolean at least in slow_user_access. 
Or in fact just call it pwrite instead of write to reflect pwrite == 
true is _reading_ from user memory.

> +	while (remain > 0) {
> +		/* Operation in this page
> +		 *
> +		 * page_base = page offset within aperture
> +		 * page_offset = offset within page
> +		 * page_length = bytes to copy for this page
> +		 */
> +		page_base = offset & PAGE_MASK;
> +		page_offset = offset_in_page(offset);
> +		page_length = remain;
> +		if ((page_offset + remain) > PAGE_SIZE)
> +			page_length = PAGE_SIZE - page_offset;

It would save some arithmetics and branching to pull out the first 
potentially unaligned copy out of the loop and then page_offset would be 
zero for 2nd page onwards.

> +		/* 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, write);
> +
> +		if (ret) {
> +			ret = -EINVAL;
> +			break;
> +		}
> +
> +		remain -= page_length;
> +		user_data += page_length;
> +		offset += page_length;
> +	}
> +
> +	mutex_lock(&dev->struct_mutex);

Caller had it interruptible.

> +
> +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,
> @@ -752,17 +848,19 @@ 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) {
> +		if (obj->tiling_mode == I915_TILING_NONE)
> +			ret = i915_gem_gtt_pread_pwrite(dev, obj, args->size,
> +							args->offset,
> +							args->data_ptr,
> +							false);
> +		else
> +			ret = -EINVAL;
> +	} else
> +		ret = i915_gem_shmem_pread(dev, obj, args, file);

Same coding style disagreement on whether or not both blocks should have 
braces.

Regards,

Tvrtko
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Re: [PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem backed objects

[Chris Wilson]

On Wed, Jul 01, 2015 at 02:55:47PM +0530, ankitprasad.r.sharma@intel.com wrote:
> -	ret = i915_gem_shmem_pread(dev, obj, args, file);
> +	/* pread for non shmem backed objects */
> +	if (!obj->base.filp) {
> +		if (obj->tiling_mode == I915_TILING_NONE)
> +			ret = i915_gem_gtt_pread_pwrite(dev, obj, args->size,
> +							args->offset,
> +							args->data_ptr,
> +							false);
> +		else
> +			ret = -EINVAL;
> +	} else
> +		ret = i915_gem_shmem_pread(dev, obj, args, file);

My preference for structuring this would be to always try the faster
method and move the can-gtt/can-shm tests into that method and then try the
slow path for suitable errno.

That way with the refactoring here, we place all the knowledge of what
objects work with the GTT access inside the GTT accessor. Similarly
wrt to the fast shmem read path.

For extra fun, we can directly read from stolen physical addresses for
gen<6.

Overall the patch lgtm, though I have some cleanups pending to the GTT
access path to handle huge objects - the ordering of those with this
doesn't matter.
-Chris

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[PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem backed objects

[ankitprasad.r.sharma]

From: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>

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 prime objects as well as stolen memory backed objects
but for userptr objects it is still forbidden.

v2: drop locks around slow_user_access, prefault the pages before
access (Chris)

v3: Rebased to the latest drm-intel-nightly (Ankit)

testcase: igt/gem_stolen

Signed-off-by: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>
---
 drivers/gpu/drm/i915/i915_gem.c | 137 +++++++++++++++++++++++++++++++++++-----
 1 file changed, 120 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 4acf331..4be6eb4 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -629,6 +629,102 @@ shmem_pread_slow(struct page *page, int shmem_page_offset, int page_length,
 	return ret ? - EFAULT : 0;
 }
 
+static inline int
+slow_user_access(struct io_mapping *mapping,
+		 loff_t page_base, int page_offset,
+		 char __user *user_data,
+		 int length, bool write)
+{
+	void __iomem *vaddr_inatomic;
+	void *vaddr;
+	unsigned long 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 (write)
+		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_pread_pwrite(struct drm_device *dev,
+			  struct drm_i915_gem_object *obj, uint64_t size,
+			  uint64_t data_offset, uint64_t data_ptr, bool write)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	char __user *user_data;
+	ssize_t remain;
+	loff_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, write);
+	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;
+
+	if (write)
+		intel_fb_obj_invalidate(obj, ORIGIN_GTT);
+
+	mutex_unlock(&dev->struct_mutex);
+	if (!write && likely(!i915.prefault_disable))
+		ret = fault_in_multipages_writeable(user_data, remain);
+
+	while (remain > 0) {
+		/* Operation in this page
+		 *
+		 * page_base = page offset within aperture
+		 * page_offset = offset within page
+		 * page_length = bytes to copy for this page
+		 */
+		page_base = offset & PAGE_MASK;
+		page_offset = offset_in_page(offset);
+		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, write);
+
+		if (ret) {
+			ret = -EINVAL;
+			break;
+		}
+
+		remain -= page_length;
+		user_data += page_length;
+		offset += page_length;
+	}
+
+	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,
@@ -752,17 +848,19 @@ 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) {
+		if (obj->tiling_mode == I915_TILING_NONE)
+			ret = i915_gem_gtt_pread_pwrite(dev, obj, args->size,
+							args->offset,
+							args->data_ptr,
+							false);
+		else
+			ret = -EINVAL;
+	} else
+		ret = i915_gem_shmem_pread(dev, obj, args, file);
 
 out:
 	drm_gem_object_unreference(&obj->base);
@@ -1103,17 +1201,22 @@ i915_gem_pwrite_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_pwrite(obj, args->offset, args->size);
 
 	ret = -EFAULT;
+
+	/* pwrite for non shmem backed objects */
+	if (!obj->base.filp) {
+		if (obj->tiling_mode == I915_TILING_NONE)
+			ret = i915_gem_gtt_pread_pwrite(dev, obj, args->size,
+							args->offset,
+							args->data_ptr,
+							true);
+		else
+			ret = -EINVAL;
+
+		goto out;
+	}
 	/* 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.
-- 
1.9.1

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