[Intel-gfx] [PATCH 1/2] drm/i915/bxt: prevent allocating context object from HIGHMEM

[Imre Deak]

At least on BXT A stepping we need to map part of the context object as
uncached. For this we first set the corresponding page to uncached and
then use kmap/kunmap to get a kernel mapping whenever we want to update
the context. Since kmap for a HIGHMEM page always returns a write-back
mapping we need to prevent allocating the context object from HIGHMEM.

Needed by the next patch implementing the actual workaround for BXT A.

Signed-off-by: Imre Deak <imre.deak at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h  |  2 ++
 drivers/gpu/drm/i915/i915_gem.c  | 21 ++++++++++++++++++---
 drivers/gpu/drm/i915/intel_lrc.c |  5 ++++-
 3 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 4ea3e7b..6e7f91e 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2806,6 +2806,8 @@ void i915_gem_object_init(struct drm_i915_gem_object *obj,
 			 const struct drm_i915_gem_object_ops *ops);
 struct drm_i915_gem_object *i915_gem_alloc_object(struct drm_device *dev,
 						  size_t size);
+struct drm_i915_gem_object *
+i915_gem_alloc_object_no_highmem(struct drm_device *dev, size_t size);
 struct drm_i915_gem_object *i915_gem_object_create_from_data(
 		struct drm_device *dev, const void *data, size_t size);
 void i915_init_vm(struct drm_i915_private *dev_priv,
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index cb0df7e..11c9191 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4243,8 +4243,8 @@ static const struct drm_i915_gem_object_ops i915_gem_object_ops = {
 	.put_pages = i915_gem_object_put_pages_gtt,
 };
 
-struct drm_i915_gem_object *i915_gem_alloc_object(struct drm_device *dev,
-						  size_t size)
+static struct drm_i915_gem_object *
+__i915_gem_alloc_object(struct drm_device *dev, size_t size, bool highmem)
 {
 	struct drm_i915_gem_object *obj;
 	struct address_space *mapping;
@@ -4262,10 +4262,13 @@ struct drm_i915_gem_object *i915_gem_alloc_object(struct drm_device *dev,
 	mask = GFP_HIGHUSER | __GFP_RECLAIMABLE;
 	if (IS_CRESTLINE(dev) || IS_BROADWATER(dev)) {
 		/* 965gm cannot relocate objects above 4GiB. */
-		mask &= ~__GFP_HIGHMEM;
+		highmem = false;
 		mask |= __GFP_DMA32;
 	}
 
+	if (!highmem)
+		mask &= ~__GFP_HIGHMEM;
+
 	mapping = file_inode(obj->base.filp)->i_mapping;
 	mapping_set_gfp_mask(mapping, mask);
 
@@ -4296,6 +4299,18 @@ struct drm_i915_gem_object *i915_gem_alloc_object(struct drm_device *dev,
 	return obj;
 }
 
+struct drm_i915_gem_object *
+i915_gem_alloc_object(struct drm_device *dev, size_t size)
+{
+	return __i915_gem_alloc_object(dev, size, true);
+}
+
+struct drm_i915_gem_object *
+i915_gem_alloc_object_no_highmem(struct drm_device *dev, size_t size)
+{
+	return __i915_gem_alloc_object(dev, size, false);
+}
+
 static bool discard_backing_storage(struct drm_i915_gem_object *obj)
 {
 	/* If we are the last user of the backing storage (be it shmemfs
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index fe06accb0..942069f 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -2459,7 +2459,10 @@ int intel_lr_context_deferred_alloc(struct intel_context *ctx,
 	/* One extra page as the sharing data between driver and GuC */
 	context_size += PAGE_SIZE * LRC_PPHWSP_PN;
 
-	ctx_obj = i915_gem_alloc_object(dev, context_size);
+	if (IS_BROXTON(dev) && INTEL_REVID(dev) < BXT_REVID_B0)
+		ctx_obj = i915_gem_alloc_object_no_highmem(dev, context_size);
+	else
+		ctx_obj = i915_gem_alloc_object(dev, context_size);
 	if (!ctx_obj) {
 		DRM_DEBUG_DRIVER("Alloc LRC backing obj failed.\n");
 		return -ENOMEM;
-- 
2.1.4