drm/i915/gvt: scan non-privileged batch buffer for debug purpose

For perfomance purpose, scanning of non-privileged batch buffer is turned
off by default. But for debugging purpose, it can be turned on via debugfs.
After scanning, we submit the original non-privileged batch buffer into
hardware, so that the scanning is only a peeking window of guest submitted
commands and will not affect the execution results.

v4:
- refine debugfs print format&content (zhenyu wang)
- print engine id instread of engine name to prevent potential memory leak
  in debugfs warning message. (zhenyu wang)

v3:
- change vgpu->scan_nonprivbb from type bool to u32, so it is able to
  selectively turn on/off scanning of non-privileged batch buffer on engine
  level. e.g.
  if vgpu->scan_nonprivbb=3, then it will scan non-privileged batch buffer
  on engine 0 and 1.
- in debugfs interface to set vgpu->scan_nonprivbb, print warning message
  to warn user and explicitly tell state change in kernel log (zhenyu wang)
v2:
- rebase
- update comments for start_gma_offset (henry)

Signed-off-by: Zhao Yan <yan.y.zhao@intel.com>
Reviewed-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Zhi Wang <zhi.a.wang@intel.com>

1 files changed, 67 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/gvt/debugfs.c b/drivers/gpu/drm/i915/gvt/debugfs.c
index f7d0078eb61b..2ec89bcb59f1 100644
--- a/drivers/gpu/drm/i915/gvt/debugfs.c
+++ b/drivers/gpu/drm/i915/gvt/debugfs.c
@@ -124,6 +124,68 @@ static int vgpu_mmio_diff_show(struct seq_file *s, void *unused)
 }
 DEFINE_SHOW_ATTRIBUTE(vgpu_mmio_diff);
 
+static int
+vgpu_scan_nonprivbb_get(void *data, u64 *val)
+{
+	struct intel_vgpu *vgpu = (struct intel_vgpu *)data;
+	*val = vgpu->scan_nonprivbb;
+	return 0;
+}
+
+/*
+ * set/unset bit engine_id of vgpu->scan_nonprivbb to turn on/off scanning
+ * of non-privileged batch buffer. e.g.
+ * if vgpu->scan_nonprivbb=3, then it will scan non-privileged batch buffer
+ * on engine 0 and 1.
+ */
+static int
+vgpu_scan_nonprivbb_set(void *data, u64 val)
+{
+	struct intel_vgpu *vgpu = (struct intel_vgpu *)data;
+	struct drm_i915_private *dev_priv = vgpu->gvt->dev_priv;
+	enum intel_engine_id id;
+	char buf[128], *s;
+	int len;
+
+	val &= (1 << I915_NUM_ENGINES) - 1;
+
+	if (vgpu->scan_nonprivbb == val)
+		return 0;
+
+	if (!val)
+		goto done;
+
+	len = sprintf(buf,
+		"gvt: vgpu %d turns on non-privileged batch buffers scanning on Engines:",
+		vgpu->id);
+
+	s = buf + len;
+
+	for (id = 0; id < I915_NUM_ENGINES; id++) {
+		struct intel_engine_cs *engine;
+
+		engine = dev_priv->engine[id];
+		if (engine && (val & (1 << id))) {
+			len = snprintf(s, 4, "%d, ", engine->id);
+			s += len;
+		} else
+			val &=  ~(1 << id);
+	}
+
+	if (val)
+		sprintf(s, "low performance expected.");
+
+	pr_warn("%s\n", buf);
+
+done:
+	vgpu->scan_nonprivbb = val;
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(vgpu_scan_nonprivbb_fops,
+			vgpu_scan_nonprivbb_get, vgpu_scan_nonprivbb_set,
+			"0x%llx\n");
+
 /**
  * intel_gvt_debugfs_add_vgpu - register debugfs entries for a vGPU
  * @vgpu: a vGPU
@@ -151,6 +213,11 @@ int intel_gvt_debugfs_add_vgpu(struct intel_vgpu *vgpu)
 	if (!ent)
 		return -ENOMEM;
 
+	ent = debugfs_create_file("scan_nonprivbb", 0644, vgpu->debugfs,
+				 vgpu, &vgpu_scan_nonprivbb_fops);
+	if (!ent)
+		return -ENOMEM;
+
 	return 0;
 }