drm/i915: add a context parameter to {en, dis}able zero address mapping

Export a new context parameter that can be set/queried through the
context_{get,set}param ioctls.  This parameter is passed as a context
flag and decides whether or not a GPU address mapping is allowed to
be made at address zero.  The default is to allow such mappings.
Signed-off-by: David Weinehall <david.weinehall@intel.com>
Acked-by: "Zou, Nanhai" <nanhai.zou@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.h

@@ -805,11 +805,15 @@ struct i915_ctx_hang_stats {
 
 /* This must match up with the value previously used for execbuf2.rsvd1. */
 #define DEFAULT_CONTEXT_HANDLE 0
+
+#define CONTEXT_NO_ZEROMAP (1<<0)
 /**
  * struct intel_context - as the name implies, represents a context.
  * @ref: reference count.
  * @user_handle: userspace tracking identity for this context.
  * @remap_slice: l3 row remapping information.
+ * @flags: context specific flags:
+ *         CONTEXT_NO_ZEROMAP: do not allow mapping things to page 0.
  * @file_priv: filp associated with this context (NULL for global default
  *	       context).
  * @hang_stats: information about the role of this context in possible GPU
@@ -826,6 +830,7 @@ struct intel_context {
 	struct kref ref;
 	int user_handle;
 	uint8_t remap_slice;
+	int flags;
 	struct drm_i915_file_private *file_priv;
 	struct i915_ctx_hang_stats hang_stats;
 	struct i915_hw_ppgtt *ppgtt;

drivers/gpu/drm/i915/i915_gem_context.c

@@ -900,6 +900,9 @@ int i915_gem_context_getparam_ioctl(struct drm_device *dev, void *data,
 	case I915_CONTEXT_PARAM_BAN_PERIOD:
 		args->value = ctx->hang_stats.ban_period_seconds;
 		break;
+	case I915_CONTEXT_PARAM_NO_ZEROMAP:
+		args->value = ctx->flags & CONTEXT_NO_ZEROMAP;
+		break;
 	default:
 		ret = -EINVAL;
 		break;
@@ -937,6 +940,14 @@ int i915_gem_context_setparam_ioctl(struct drm_device *dev, void *data,
 		else
 			ctx->hang_stats.ban_period_seconds = args->value;
 		break;
+	case I915_CONTEXT_PARAM_NO_ZEROMAP:
+		if (args->size) {
+			ret = -EINVAL;
+		} else {
+			ctx->flags &= ~CONTEXT_NO_ZEROMAP;
+			ctx->flags |= args->value ? CONTEXT_NO_ZEROMAP : 0;
+		}
+		break;
 	default:
 		ret = -EINVAL;
 		break;

drivers/gpu/drm/i915/i915_gem_execbuffer.c

@@ -676,6 +676,7 @@ eb_vma_misplaced(struct i915_vma *vma)
 static int
 i915_gem_execbuffer_reserve(struct intel_engine_cs *ring,
 			    struct list_head *vmas,
+			    struct intel_context *ctx,
 			    bool *need_relocs)
 {
 	struct drm_i915_gem_object *obj;
@@ -698,6 +699,9 @@ i915_gem_execbuffer_reserve(struct intel_engine_cs *ring,
 		obj = vma->obj;
 		entry = vma->exec_entry;
 
+		if (ctx->flags & CONTEXT_NO_ZEROMAP)
+			entry->flags |= __EXEC_OBJECT_NEEDS_BIAS;
+
 		if (!has_fenced_gpu_access)
 			entry->flags &= ~EXEC_OBJECT_NEEDS_FENCE;
 		need_fence =
@@ -775,7 +779,8 @@ i915_gem_execbuffer_relocate_slow(struct drm_device *dev,
 				  struct drm_file *file,
 				  struct intel_engine_cs *ring,
 				  struct eb_vmas *eb,
-				  struct drm_i915_gem_exec_object2 *exec)
+				  struct drm_i915_gem_exec_object2 *exec,
+				  struct intel_context *ctx)
 {
 	struct drm_i915_gem_relocation_entry *reloc;
 	struct i915_address_space *vm;
@@ -861,7 +866,7 @@ i915_gem_execbuffer_relocate_slow(struct drm_device *dev,
 		goto err;
 
 	need_relocs = (args->flags & I915_EXEC_NO_RELOC) == 0;
-	ret = i915_gem_execbuffer_reserve(ring, &eb->vmas, &need_relocs);
+	ret = i915_gem_execbuffer_reserve(ring, &eb->vmas, ctx, &need_relocs);
 	if (ret)
 		goto err;
 
@@ -1519,7 +1524,7 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 
 	/* Move the objects en-masse into the GTT, evicting if necessary. */
 	need_relocs = (args->flags & I915_EXEC_NO_RELOC) == 0;
-	ret = i915_gem_execbuffer_reserve(ring, &eb->vmas, &need_relocs);
+	ret = i915_gem_execbuffer_reserve(ring, &eb->vmas, ctx, &need_relocs);
 	if (ret)
 		goto err;
 
@@ -1529,7 +1534,7 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 	if (ret) {
 		if (ret == -EFAULT) {
 			ret = i915_gem_execbuffer_relocate_slow(dev, args, file, ring,
-								eb, exec);
+								eb, exec, ctx);
 			BUG_ON(!mutex_is_locked(&dev->struct_mutex));
 		}
 		if (ret)

include/uapi/drm/i915_drm.h

@@ -1106,6 +1106,7 @@ struct drm_i915_gem_context_param {
 	__u32 size;
 	__u64 param;
 #define I915_CONTEXT_PARAM_BAN_PERIOD 0x1
+#define I915_CONTEXT_PARAM_NO_ZEROMAP 0x2
 	__u64 value;
 };