drm/i915/gvt: Provide generic page_track infrastructure for write-protected page

This patch provide generic page_track infrastructure for write-protected
guest page. The old page_track logic gets rewrote and now stays in a new
standalone page_track.c. This page track infrastructure can be both used
by vGUC and GTT shadowing.

The important change is that it uses radix tree instead of hash table.
We don't have a predictable number of pages that will be tracked.

Here is some performance data (duration in us) of looking up a element:
Before: (aka. intel_vgpu_find_tracked_page)
 0.091 0.089 0.090 ... 0.093 0.091 0.087 ... 0.292 0.285 0.292 0.291
After: (aka. intel_vgpu_find_page_track)
 0.104 0.105 0.100 0.102 0.102 0.100 ... 0.101 0.101 0.105 0.105

The hash table has good performance at beginning, but turns bad with
more pages being tracked even no 3D applications are running. As
expected, radix tree has stable duration and very quick.

The overall benchmark (tested with Heaven Benchmark) marginally improved
since this is not the bottleneck. What we benefit more from this change
is scalability.

Signed-off-by: Changbin Du <changbin.du@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

1 files changed, 181 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/gvt/page_track.c b/drivers/gpu/drm/i915/gvt/page_track.c
new file mode 100644
index 000000000000..09bd56e39ec6
--- /dev/null
+++ b/drivers/gpu/drm/i915/gvt/page_track.c
@@ -0,0 +1,181 @@
+/*
+ * Copyright(c) 2011-2017 Intel Corporation. All rights reserved.
+ *
+ * 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.
+ */
+#include "i915_drv.h"
+#include "gvt.h"
+
+/**
+ * intel_vgpu_find_page_track - find page track rcord of guest page
+ * @vgpu: a vGPU
+ * @gfn: the gfn of guest page
+ *
+ * Returns:
+ * A pointer to struct intel_vgpu_page_track if found, else NULL returned.
+ */
+struct intel_vgpu_page_track *intel_vgpu_find_page_track(
+		struct intel_vgpu *vgpu, unsigned long gfn)
+{
+	return radix_tree_lookup(&vgpu->page_track_tree, gfn);
+}
+
+/**
+ * intel_vgpu_register_page_track - register a guest page to be tacked
+ * @vgpu: a vGPU
+ * @gfn: the gfn of guest page
+ *
+ * Returns:
+ * zero on success, negative error code if failed.
+ */
+int intel_vgpu_register_page_track(struct intel_vgpu *vgpu, unsigned long gfn,
+		gvt_page_track_handler_t handler, void *priv)
+{
+	struct intel_vgpu_page_track *track;
+	int ret;
+
+	track = intel_vgpu_find_page_track(vgpu, gfn);
+	if (track)
+		return -EEXIST;
+
+	track = kzalloc(sizeof(*track), GFP_KERNEL);
+	if (!track)
+		return -ENOMEM;
+
+	track->handler = handler;
+	track->priv_data = priv;
+
+	ret = radix_tree_insert(&vgpu->page_track_tree, gfn, track);
+	if (ret) {
+		kfree(track);
+		return ret;
+	}
+
+	return 0;
+}
+
+/**
+ * intel_vgpu_unregister_page_track - unregister the tracked guest page
+ * @vgpu: a vGPU
+ * @gfn: the gfn of guest page
+ *
+ */
+void intel_vgpu_unregister_page_track(struct intel_vgpu *vgpu,
+		unsigned long gfn)
+{
+	struct intel_vgpu_page_track *track;
+
+	track = radix_tree_delete(&vgpu->page_track_tree, gfn);
+	if (track) {
+		if (track->tracked)
+			intel_gvt_hypervisor_disable_page_track(vgpu, gfn);
+		kfree(track);
+	}
+}
+
+/**
+ * intel_vgpu_enable_page_track - set write-protection on guest page
+ * @vgpu: a vGPU
+ * @gfn: the gfn of guest page
+ *
+ * Returns:
+ * zero on success, negative error code if failed.
+ */
+int intel_vgpu_enable_page_track(struct intel_vgpu *vgpu, unsigned long gfn)
+{
+	struct intel_vgpu_page_track *track;
+	int ret;
+
+	track = intel_vgpu_find_page_track(vgpu, gfn);
+	if (!track)
+		return -ENXIO;
+
+	if (track->tracked)
+		return 0;
+
+	ret = intel_gvt_hypervisor_enable_page_track(vgpu, gfn);
+	if (ret)
+		return ret;
+	track->tracked = true;
+	return 0;
+}
+
+/**
+ * intel_vgpu_enable_page_track - cancel write-protection on guest page
+ * @vgpu: a vGPU
+ * @gfn: the gfn of guest page
+ *
+ * Returns:
+ * zero on success, negative error code if failed.
+ */
+int intel_vgpu_disable_page_track(struct intel_vgpu *vgpu, unsigned long gfn)
+{
+	struct intel_vgpu_page_track *track;
+	int ret;
+
+	track = intel_vgpu_find_page_track(vgpu, gfn);
+	if (!track)
+		return -ENXIO;
+
+	if (!track->tracked)
+		return 0;
+
+	ret = intel_gvt_hypervisor_disable_page_track(vgpu, gfn);
+	if (ret)
+		return ret;
+	track->tracked = false;
+	return 0;
+}
+
+/**
+ * intel_vgpu_page_track_handler - called when write to write-protected page
+ * @vgpu: a vGPU
+ * @gpa: the gpa of this write
+ * @data: the writed data
+ * @bytes: the length of this write
+ *
+ * Returns:
+ * zero on success, negative error code if failed.
+ */
+int intel_vgpu_page_track_handler(struct intel_vgpu *vgpu, u64 gpa,
+		void *data, unsigned int bytes)
+{
+	struct intel_gvt *gvt = vgpu->gvt;
+	struct intel_vgpu_page_track *page_track;
+	int ret = 0;
+
+	mutex_lock(&gvt->lock);
+
+	page_track = intel_vgpu_find_page_track(vgpu, gpa >> PAGE_SHIFT);
+	if (!page_track)
+		return 0;
+
+	if (unlikely(vgpu->failsafe)) {
+		/* Remove write protection to prevent furture traps. */
+		intel_vgpu_disable_page_track(vgpu, gpa >> PAGE_SHIFT);
+	} else {
+		ret = page_track->handler(page_track, gpa, data, bytes);
+		if (ret)
+			gvt_err("guest page write error, gpa %llx\n", gpa);
+	}
+
+	mutex_unlock(&gvt->lock);
+	return ret;
+}