From a03f395ad78f883df490234366dd4e4fc922d174 Mon Sep 17 00:00:00 2001
From: Tina Zhang <tina.zhang@intel.com>
Date: Tue, 14 Nov 2017 10:25:13 +0000
Subject: [PATCH] drm/i915: Introduce GEM proxy
Git-commit: a03f395ad78f883df490234366dd4e4fc922d174
Patch-mainline: v4.16-rc1
References: FATE#322643 bsc#1055900

GEM proxy is a kind of GEM, whose backing physical memory is pinned
and produced by guest VM and is used by host as read only. With GEM
proxy, host is able to access guest physical memory through GEM object
interface. As GEM proxy is such a special kind of GEM, a new flag
I915_GEM_OBJECT_IS_PROXY is introduced to ban host from changing the
backing storage of GEM proxy.

V3: 
- update "Reviewed-by". (Joonas)

V2: 
- return -ENXIO when pin and map pages of GEM proxy to kernel space.
  (Chris)

Here are the histories of this patch in "Dma-buf support for Gvt-g"
Patch-set: 

V14: 
- return -ENXIO when gem proxy object is banned by ioctl.
  (Chris) (Daniel)

V13: 
- add comments to GEM proxy. (Chris)
- don't ban GEM proxy in i915_gem_sw_finish_ioctl. (Chris)
- check GEM proxy bar after finishing i915_gem_object_wait. (Chris)
- remove GEM proxy bar in i915_gem_madvise_ioctl.

V6: 
- add gem proxy barrier in the following ioctls. (Chris)
  i915_gem_set_caching_ioctl
  i915_gem_set_domain_ioctl
  i915_gem_sw_finish_ioctl
  i915_gem_set_tiling_ioctl
  i915_gem_madvise_ioctl

Signed-off-by: Tina Zhang <tina.zhang@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> #v1
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/1510555798-21079-2-git-send-email-tina.zhang@intel.com
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171114102513.22269-2-chris@chris-wilson.co.uk
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/i915_gem.c        |   31 +++++++++++++++++++++++++++++--
 drivers/gpu/drm/i915/i915_gem_object.h |   11 +++++++++--
 drivers/gpu/drm/i915/i915_gem_tiling.c |    9 +++++++++
 3 files changed, 47 insertions(+), 4 deletions(-)

--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1612,7 +1612,19 @@ i915_gem_set_domain_ioctl(struct drm_dev
 	if (err)
 		goto out;
 
-	/* Flush and acquire obj->pages so that we are coherent through
+	/*
+	 * Proxy objects do not control access to the backing storage, ergo
+	 * they cannot be used as a means to manipulate the cache domain
+	 * tracking for that backing storage. The proxy object is always
+	 * considered to be outside of any cache domain.
+	 */
+	if (i915_gem_object_is_proxy(obj)) {
+		err = -ENXIO;
+		goto out;
+	}
+
+	/*
+	 * Flush and acquire obj->pages so that we are coherent through
 	 * direct access in memory with previous cached writes through
 	 * shmemfs and that our cache domain tracking remains valid.
 	 * For example, if the obj->filp was moved to swap without us
@@ -1668,6 +1680,11 @@ i915_gem_sw_finish_ioctl(struct drm_devi
 	if (!obj)
 		return -ENOENT;
 
+	/*
+	 * Proxy objects are barred from CPU access, so there is no
+	 * need to ban sw_finish as it is a nop.
+	 */
+
 	/* Pinned buffers may be scanout, so flush the cache */
 	i915_gem_object_flush_if_display(obj);
 	i915_gem_object_put(obj);
@@ -2662,7 +2679,8 @@ void *i915_gem_object_pin_map(struct drm
 	void *ptr;
 	int ret;
 
-	GEM_BUG_ON(!i915_gem_object_has_struct_page(obj));
+	if (unlikely(!i915_gem_object_has_struct_page(obj)))
+		return ERR_PTR(-ENXIO);
 
 	ret = mutex_lock_interruptible(&obj->mm.lock);
 	if (ret)
@@ -3881,6 +3899,15 @@ int i915_gem_set_caching_ioctl(struct dr
 	if (!obj)
 		return -ENOENT;
 
+	/*
+	 * The caching mode of proxy object is handled by its generator, and
+	 * not allowed to be changed by userspace.
+	 */
+	if (i915_gem_object_is_proxy(obj)) {
+		ret = -ENXIO;
+		goto out;
+	}
+
 	if (obj->cache_level == level)
 		goto out;
 
--- a/drivers/gpu/drm/i915/i915_gem_object.h
+++ b/drivers/gpu/drm/i915/i915_gem_object.h
@@ -53,8 +53,9 @@ struct i915_lut_handle {
 
 struct drm_i915_gem_object_ops {
 	unsigned int flags;
-#define I915_GEM_OBJECT_HAS_STRUCT_PAGE BIT(0)
-#define I915_GEM_OBJECT_IS_SHRINKABLE   BIT(1)
+#define I915_GEM_OBJECT_HAS_STRUCT_PAGE	BIT(0)
+#define I915_GEM_OBJECT_IS_SHRINKABLE	BIT(1)
+#define I915_GEM_OBJECT_IS_PROXY	BIT(2)
 
 	/* Interface between the GEM object and its backing storage.
 	 * get_pages() is called once prior to the use of the associated set
@@ -362,6 +363,12 @@ i915_gem_object_is_shrinkable(const stru
 }
 
 static inline bool
+i915_gem_object_is_proxy(const struct drm_i915_gem_object *obj)
+{
+	return obj->ops->flags & I915_GEM_OBJECT_IS_PROXY;
+}
+
+static inline bool
 i915_gem_object_is_active(const struct drm_i915_gem_object *obj)
 {
 	return obj->active_count;
--- a/drivers/gpu/drm/i915/i915_gem_tiling.c
+++ b/drivers/gpu/drm/i915/i915_gem_tiling.c
@@ -345,6 +345,15 @@ i915_gem_set_tiling_ioctl(struct drm_dev
 	if (!obj)
 		return -ENOENT;
 
+	/*
+	 * The tiling mode of proxy objects is handled by its generator, and
+	 * not allowed to be changed by userspace.
+	 */
+	if (i915_gem_object_is_proxy(obj)) {
+		err = -ENXIO;
+		goto err;
+	}
+
 	if (!i915_tiling_ok(obj, args->tiling_mode, args->stride)) {
 		err = -EINVAL;
 		goto err;