drm/i915: Mark CPU cache as dirty on every transition for CPU writes

Currently, we only mark the CPU cache as dirty if we skip a clflush.
This leads to some confusion where we have to ask if the object is in
the write domain or missed a clflush. If we always mark the cache as
dirty, this becomes a much simply question to answer.

The goal remains to do as few clflushes as required and to do them as
late as possible, in the hope of deferring the work to a kthread and not
block the caller (e.g. execbuf, flips).

v2: Always call clflush before GPU execution when the cache_dirty flag
is set. This may cause some extra work on llc systems that migrate dirty
buffers back and forth - but we do try to limit that by only setting
cache_dirty at the end of the gpu sequence.

v3: Always mark the cache as dirty upon a level change, as we need to
invalidate any stale cachelines due to external writes.

Reported-by: Dongwon Kim <dongwon.kim@intel.com>
Fixes: a6a7cc4b7db6 ("drm/i915: Always flush the dirty CPU cache when pinning the scanout")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Dongwon Kim <dongwon.kim@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Tested-by: Dongwon Kim <dongwon.kim@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170615123850.26843-1-chris@chris-wilson.co.uk
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 31cbe78171a99f50b8a1b2993f30bf8ac201386a..b1504a829c6a1e7e06c4a17f0759bac9ada93a77 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -49,7 +49,7 @@ static void i915_gem_flush_free_objects(struct drm_i915_private *i915);
 
 static bool cpu_write_needs_clflush(struct drm_i915_gem_object *obj)
 {
-       if (obj->base.write_domain == I915_GEM_DOMAIN_CPU)
+       if (obj->cache_dirty)
                return false;
 
        if (!i915_gem_object_is_coherent(obj))
@@ -233,6 +233,14 @@ err_phys:
        return st;
 }
 
+static void __start_cpu_write(struct drm_i915_gem_object *obj)
+{
+       obj->base.read_domains = I915_GEM_DOMAIN_CPU;
+       obj->base.write_domain = I915_GEM_DOMAIN_CPU;
+       if (cpu_write_needs_clflush(obj))
+               obj->cache_dirty = true;
+}
+
 static void
 __i915_gem_object_release_shmem(struct drm_i915_gem_object *obj,
                                struct sg_table *pages,
@@ -248,8 +256,7 @@ __i915_gem_object_release_shmem(struct drm_i915_gem_object *obj,
            !i915_gem_object_is_coherent(obj))
                drm_clflush_sg(pages);
 
-       obj->base.read_domains = I915_GEM_DOMAIN_CPU;
-       obj->base.write_domain = I915_GEM_DOMAIN_CPU;
+       __start_cpu_write(obj);
 }
 
 static void
@@ -684,6 +691,12 @@ i915_gem_dumb_create(struct drm_file *file,
                               args->size, &args->handle);
 }
 
+static bool gpu_write_needs_clflush(struct drm_i915_gem_object *obj)
+{
+       return !(obj->cache_level == I915_CACHE_NONE ||
+                obj->cache_level == I915_CACHE_WT);
+}
+
 /**
  * Creates a new mm object and returns a handle to it.
  * @dev: drm device pointer
@@ -753,6 +766,11 @@ flush_write_domain(struct drm_i915_gem_object *obj, unsigned int flush_domains)
        case I915_GEM_DOMAIN_CPU:
                i915_gem_clflush_object(obj, I915_CLFLUSH_SYNC);
                break;
+
+       case I915_GEM_DOMAIN_RENDER:
+               if (gpu_write_needs_clflush(obj))
+                       obj->cache_dirty = true;
+               break;
        }
 
        obj->base.write_domain = 0;
@@ -854,7 +872,8 @@ int i915_gem_obj_prepare_shmem_read(struct drm_i915_gem_object *obj,
         * optimizes for the case when the gpu will dirty the data
         * anyway again before the next pread happens.
         */
-       if (!(obj->base.read_domains & I915_GEM_DOMAIN_CPU))
+       if (!obj->cache_dirty &&
+           !(obj->base.read_domains & I915_GEM_DOMAIN_CPU))
                *needs_clflush = CLFLUSH_BEFORE;
 
 out:
@@ -906,14 +925,16 @@ int i915_gem_obj_prepare_shmem_write(struct drm_i915_gem_object *obj,
         * This optimizes for the case when the gpu will use the data
         * right away and we therefore have to clflush anyway.
         */
-       if (obj->base.write_domain != I915_GEM_DOMAIN_CPU)
+       if (!obj->cache_dirty) {
                *needs_clflush |= CLFLUSH_AFTER;
 
-       /* Same trick applies to invalidate partially written cachelines read
-        * before writing.
-        */
-       if (!(obj->base.read_domains & I915_GEM_DOMAIN_CPU))
-               *needs_clflush |= CLFLUSH_BEFORE;
+               /*
+                * Same trick applies to invalidate partially written
+                * cachelines read before writing.
+                */
+               if (!(obj->base.read_domains & I915_GEM_DOMAIN_CPU))
+                       *needs_clflush |= CLFLUSH_BEFORE;
+       }
 
 out:
        intel_fb_obj_invalidate(obj, ORIGIN_CPU);
@@ -3395,10 +3416,13 @@ int i915_gem_wait_for_idle(struct drm_i915_private *i915, unsigned int flags)
 
 static void __i915_gem_object_flush_for_display(struct drm_i915_gem_object *obj)
 {
-       if (obj->base.write_domain != I915_GEM_DOMAIN_CPU && !obj->cache_dirty)
-               return;
-
-       i915_gem_clflush_object(obj, I915_CLFLUSH_FORCE);
+       /*
+        * We manually flush the CPU domain so that we can override and
+        * force the flush for the display, and perform it asyncrhonously.
+        */
+       flush_write_domain(obj, ~I915_GEM_DOMAIN_CPU);
+       if (obj->cache_dirty)
+               i915_gem_clflush_object(obj, I915_CLFLUSH_FORCE);
        obj->base.write_domain = 0;
 }
 
@@ -3657,13 +3681,10 @@ restart:
                }
        }
 
-       if (obj->base.write_domain == I915_GEM_DOMAIN_CPU &&
-           i915_gem_object_is_coherent(obj))
-               obj->cache_dirty = true;
-
        list_for_each_entry(vma, &obj->vma_list, obj_link)
                vma->node.color = cache_level;
        obj->cache_level = cache_level;
+       obj->cache_dirty = true; /* Always invalidate stale cachelines */
 
        return 0;
 }
@@ -3885,9 +3906,6 @@ i915_gem_object_set_to_cpu_domain(struct drm_i915_gem_object *obj, bool write)
        if (ret)
                return ret;
 
-       if (obj->base.write_domain == I915_GEM_DOMAIN_CPU)
-               return 0;
-
        flush_write_domain(obj, ~I915_GEM_DOMAIN_CPU);
 
        /* Flush the CPU cache if it's still invalid. */
@@ -3899,15 +3917,13 @@ i915_gem_object_set_to_cpu_domain(struct drm_i915_gem_object *obj, bool write)
        /* It should now be out of any other write domains, and we can update
         * the domain values for our changes.
         */
-       GEM_BUG_ON((obj->base.write_domain & ~I915_GEM_DOMAIN_CPU) != 0);
+       GEM_BUG_ON(obj->base.write_domain & ~I915_GEM_DOMAIN_CPU);
 
        /* If we're writing through the CPU, then the GPU read domains will
         * need to be invalidated at next use.
         */
-       if (write) {
-               obj->base.read_domains = I915_GEM_DOMAIN_CPU;
-               obj->base.write_domain = I915_GEM_DOMAIN_CPU;
-       }
+       if (write)
+               __start_cpu_write(obj);
 
        return 0;
 }
@@ -4328,6 +4344,8 @@ i915_gem_object_create(struct drm_i915_private *dev_priv, u64 size)
        } else
                obj->cache_level = I915_CACHE_NONE;
 
+       obj->cache_dirty = !i915_gem_object_is_coherent(obj);
+
        trace_i915_gem_object_create(obj);
 
        return obj;
@@ -4994,10 +5012,8 @@ int i915_gem_freeze_late(struct drm_i915_private *dev_priv)
 
        mutex_lock(&dev_priv->drm.struct_mutex);
        for (p = phases; *p; p++) {
-               list_for_each_entry(obj, *p, global_link) {
-                       obj->base.read_domains = I915_GEM_DOMAIN_CPU;
-                       obj->base.write_domain = I915_GEM_DOMAIN_CPU;
-               }
+               list_for_each_entry(obj, *p, global_link)
+                       __start_cpu_write(obj);
        }
        mutex_unlock(&dev_priv->drm.struct_mutex);
 

diff --git a/drivers/gpu/drm/i915/i915_gem_clflush.c b/drivers/gpu/drm/i915/i915_gem_clflush.c
index ffac7a1f0caf34d71588c62d88fe83f964087be6..17b207e963c283f81a204a90993b9ca9503a74c9 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_clflush.c
+++ b/drivers/gpu/drm/i915/i915_gem_clflush.c
@@ -71,8 +71,6 @@ static const struct dma_fence_ops i915_clflush_ops = {
 static void __i915_do_clflush(struct drm_i915_gem_object *obj)
 {
        drm_clflush_sg(obj->mm.pages);
-       obj->cache_dirty = false;
-
        intel_fb_obj_flush(obj, ORIGIN_CPU);
 }
 
@@ -81,9 +79,6 @@ static void i915_clflush_work(struct work_struct *work)
        struct clflush *clflush = container_of(work, typeof(*clflush), work);
        struct drm_i915_gem_object *obj = clflush->obj;
 
-       if (!obj->cache_dirty)
-               goto out;
-
        if (i915_gem_object_pin_pages(obj)) {
                DRM_ERROR("Failed to acquire obj->pages for clflushing\n");
                goto out;
@@ -131,10 +126,10 @@ void i915_gem_clflush_object(struct drm_i915_gem_object *obj,
         * anything not backed by physical memory we consider to be always
         * coherent and not need clflushing.
         */
-       if (!i915_gem_object_has_struct_page(obj))
+       if (!i915_gem_object_has_struct_page(obj)) {
+               obj->cache_dirty = false;
                return;
-
-       obj->cache_dirty = true;
+       }
 
        /* If the GPU is snooping the contents of the CPU cache,
         * we do not need to manually clear the CPU cache lines.  However,
@@ -153,6 +148,8 @@ void i915_gem_clflush_object(struct drm_i915_gem_object *obj,
        if (!(flags & I915_CLFLUSH_SYNC))
                clflush = kmalloc(sizeof(*clflush), GFP_KERNEL);
        if (clflush) {
+               GEM_BUG_ON(!obj->cache_dirty);
+
                dma_fence_init(&clflush->dma,
                               &i915_clflush_ops,
                               &clflush_lock,
@@ -180,4 +177,6 @@ void i915_gem_clflush_object(struct drm_i915_gem_object *obj,
        } else {
                GEM_BUG_ON(obj->base.write_domain != I915_GEM_DOMAIN_CPU);
        }
+
+       obj->cache_dirty = false;
 }

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 96705171e397206c02580fe8708619fbd8e80212..2a9aed5640e267f348f1368f883e53189dac85a7 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -309,7 +309,7 @@ static inline int use_cpu_reloc(struct drm_i915_gem_object *obj)
                return DBG_USE_CPU_RELOC > 0;
 
        return (HAS_LLC(to_i915(obj->base.dev)) ||
-               obj->base.write_domain == I915_GEM_DOMAIN_CPU ||
+               obj->cache_dirty ||
                obj->cache_level != I915_CACHE_NONE);
 }
 
@@ -1110,10 +1110,8 @@ eb_move_to_gpu(struct i915_execbuffer *eb)
                if (vma->exec_entry->flags & EXEC_OBJECT_ASYNC)
                        continue;
 
-               if (obj->base.write_domain & I915_GEM_DOMAIN_CPU) {
+               if (obj->cache_dirty)
                        i915_gem_clflush_object(obj, 0);
-                       obj->base.write_domain = 0;
-               }
 
                ret = i915_gem_request_await_object
                        (eb->request, obj, obj->base.pending_write_domain);
@@ -1248,12 +1246,6 @@ static int eb_select_context(struct i915_execbuffer *eb)
        return 0;
 }
 
-static bool gpu_write_needs_clflush(struct drm_i915_gem_object *obj)
-{
-       return !(obj->cache_level == I915_CACHE_NONE ||
-                obj->cache_level == I915_CACHE_WT);
-}
-
 void i915_vma_move_to_active(struct i915_vma *vma,
                             struct drm_i915_gem_request *req,
                             unsigned int flags)
@@ -1277,15 +1269,16 @@ void i915_vma_move_to_active(struct i915_vma *vma,
        i915_gem_active_set(&vma->last_read[idx], req);
        list_move_tail(&vma->vm_link, &vma->vm->active_list);
 
+       obj->base.write_domain = 0;
        if (flags & EXEC_OBJECT_WRITE) {
+               obj->base.write_domain = I915_GEM_DOMAIN_RENDER;
+
                if (intel_fb_obj_invalidate(obj, ORIGIN_CS))
                        i915_gem_active_set(&obj->frontbuffer_write, req);
 
-               /* update for the implicit flush after a batch */
-               obj->base.write_domain &= ~I915_GEM_GPU_DOMAINS;
-               if (!obj->cache_dirty && gpu_write_needs_clflush(obj))
-                       obj->cache_dirty = true;
+               obj->base.read_domains = 0;
        }
+       obj->base.read_domains |= I915_GEM_GPU_DOMAINS;
 
        if (flags & EXEC_OBJECT_NEEDS_FENCE)
                i915_gem_active_set(&vma->last_fence, req);

diff --git a/drivers/gpu/drm/i915/i915_gem_internal.c b/drivers/gpu/drm/i915/i915_gem_internal.c
index fc950abbe400ff3b821a53210fb3f4ff409a044a..58e93e87d57345c83e3a0703a4c3fe18382b76da 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_internal.c
+++ b/drivers/gpu/drm/i915/i915_gem_internal.c
@@ -188,9 +188,10 @@ i915_gem_object_create_internal(struct drm_i915_private *i915,
        drm_gem_private_object_init(&i915->drm, &obj->base, size);
        i915_gem_object_init(obj, &i915_gem_object_internal_ops);
 
-       obj->base.write_domain = I915_GEM_DOMAIN_CPU;
        obj->base.read_domains = I915_GEM_DOMAIN_CPU;
+       obj->base.write_domain = I915_GEM_DOMAIN_CPU;
        obj->cache_level = HAS_LLC(i915) ? I915_CACHE_LLC : I915_CACHE_NONE;
+       obj->cache_dirty = !i915_gem_object_is_coherent(obj);
 
        return obj;
 }

diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c
index 1a0ce1dc68f5489620801286bef18b4bf9b96fce..34461e1928bca2b6f326884b3b0ae24382f82869 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
@@ -802,9 +802,10 @@ i915_gem_userptr_ioctl(struct drm_device *dev, void *data, struct drm_file *file
 
        drm_gem_private_object_init(dev, &obj->base, args->user_size);
        i915_gem_object_init(obj, &i915_gem_userptr_ops);
-       obj->cache_level = I915_CACHE_LLC;
-       obj->base.write_domain = I915_GEM_DOMAIN_CPU;
        obj->base.read_domains = I915_GEM_DOMAIN_CPU;
+       obj->base.write_domain = I915_GEM_DOMAIN_CPU;
+       obj->cache_level = I915_CACHE_LLC;
+       obj->cache_dirty = !i915_gem_object_is_coherent(obj);
 
        obj->userptr.ptr = args->user_ptr;
        obj->userptr.read_only = !!(args->flags & I915_USERPTR_READ_ONLY);

diff --git a/drivers/gpu/drm/i915/selftests/huge_gem_object.c b/drivers/gpu/drm/i915/selftests/huge_gem_object.c
index 4e681fc13be486c528e9bcdcf7f60489a75d9c0e..0ca867a877b60c3fc9ff193457167c53ec8a41bf 100644 (file)
--- a/drivers/gpu/drm/i915/selftests/huge_gem_object.c
+++ b/drivers/gpu/drm/i915/selftests/huge_gem_object.c
@@ -126,9 +126,10 @@ huge_gem_object(struct drm_i915_private *i915,
        drm_gem_private_object_init(&i915->drm, &obj->base, dma_size);
        i915_gem_object_init(obj, &huge_ops);
 
-       obj->base.write_domain = I915_GEM_DOMAIN_CPU;
        obj->base.read_domains = I915_GEM_DOMAIN_CPU;
+       obj->base.write_domain = I915_GEM_DOMAIN_CPU;
        obj->cache_level = HAS_LLC(i915) ? I915_CACHE_LLC : I915_CACHE_NONE;
+       obj->cache_dirty = !i915_gem_object_is_coherent(obj);
        obj->scratch = phys_size;
 
        return obj;