[PATCH v2] drm/i915/gvt: Give new born vGPU higher scheduling chance

[Zhenyu Wang]

This trys to give new born vGPU with higher scheduling chance
not only with adding to sched list head and also have higher
priority for workload sched for 2 seconds after starting to
schedule it. In order for fast GPU execution during VM boot,
and ensure guest driver setup with required state given in time.

This fixes recent failure seen on one VM with multiple linux VMs running on
kernel with commit 2621cefaa42b3("drm/i915: Provide a timeout to
i915_gem_wait_for_idle() on setup"), which had shorter setup timeout
that caused context state init failed.

v2: change to 2s for higher scheduling period

Cc: Yuan Hang <hang.yuan at intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw at linux.intel.com>
---
 drivers/gpu/drm/i915/gvt/sched_policy.c | 34 ++++++++++++++++++++-----
 1 file changed, 27 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/gvt/sched_policy.c b/drivers/gpu/drm/i915/gvt/sched_policy.c
index 09d7bb72b4ff..514e075f74a7 100644
--- a/drivers/gpu/drm/i915/gvt/sched_policy.c
+++ b/drivers/gpu/drm/i915/gvt/sched_policy.c
@@ -47,11 +47,15 @@ static bool vgpu_has_pending_workload(struct intel_vgpu *vgpu)
 	return false;
 }
 
+/* We give 2 seconds higher prio for vGPU during start */
+#define GVT_SCHED_VGPU_PRI_TIME  2
+
 struct vgpu_sched_data {
 	struct list_head lru_list;
 	struct intel_vgpu *vgpu;
 	bool active;
-
+	bool pri_sched;
+	ktime_t pri_time;
 	ktime_t sched_in_time;
 	ktime_t sched_time;
 	ktime_t left_ts;
@@ -183,6 +187,14 @@ static struct intel_vgpu *find_busy_vgpu(struct gvt_sched_data *sched_data)
 		if (!vgpu_has_pending_workload(vgpu_data->vgpu))
 			continue;
 
+		if (vgpu_data->pri_sched) {
+			if (ktime_before(ktime_get(), vgpu_data->pri_time)) {
+				vgpu = vgpu_data->vgpu;
+				break;
+			} else
+				vgpu_data->pri_sched = false;
+		}
+
 		/* Return the vGPU only if it has time slice left */
 		if (vgpu_data->left_ts > 0) {
 			vgpu = vgpu_data->vgpu;
@@ -202,6 +214,7 @@ static void tbs_sched_func(struct gvt_sched_data *sched_data)
 	struct intel_gvt_workload_scheduler *scheduler = &gvt->scheduler;
 	struct vgpu_sched_data *vgpu_data;
 	struct intel_vgpu *vgpu = NULL;
+
 	/* no active vgpu or has already had a target */
 	if (list_empty(&sched_data->lru_runq_head) || scheduler->next_vgpu)
 		goto out;
@@ -209,12 +222,13 @@ static void tbs_sched_func(struct gvt_sched_data *sched_data)
 	vgpu = find_busy_vgpu(sched_data);
 	if (vgpu) {
 		scheduler->next_vgpu = vgpu;
-
-		/* Move the last used vGPU to the tail of lru_list */
 		vgpu_data = vgpu->sched_data;
-		list_del_init(&vgpu_data->lru_list);
-		list_add_tail(&vgpu_data->lru_list,
-				&sched_data->lru_runq_head);
+		if (!vgpu_data->pri_sched) {
+			/* Move the last used vGPU to the tail of lru_list */
+			list_del_init(&vgpu_data->lru_list);
+			list_add_tail(&vgpu_data->lru_list,
+				      &sched_data->lru_runq_head);
+		}
 	} else {
 		scheduler->next_vgpu = gvt->idle_vgpu;
 	}
@@ -328,11 +342,17 @@ static void tbs_sched_start_schedule(struct intel_vgpu *vgpu)
 {
 	struct gvt_sched_data *sched_data = vgpu->gvt->scheduler.sched_data;
 	struct vgpu_sched_data *vgpu_data = vgpu->sched_data;
+	ktime_t now;
 
 	if (!list_empty(&vgpu_data->lru_list))
 		return;
 
-	list_add_tail(&vgpu_data->lru_list, &sched_data->lru_runq_head);
+	now = ktime_get();
+	vgpu_data->pri_time = ktime_add(now,
+					ktime_set(GVT_SCHED_VGPU_PRI_TIME, 0));
+	vgpu_data->pri_sched = true;
+
+	list_add(&vgpu_data->lru_list, &sched_data->lru_runq_head);
 
 	if (!hrtimer_active(&sched_data->timer))
 		hrtimer_start(&sched_data->timer, ktime_add_ns(ktime_get(),
-- 
2.18.0