[PATCH 1/3] drm/i915/gvt: Use gtt_lock to protect gtt list

Colin Xu colin.xu at intel.com
Sat Mar 31 00:56:58 UTC 2018


From: Pei Zhang <pei.zhang at intel.com>

The patch set splits out 3 small locks from the original big gvt lock:
  - gtt_lock is used to protect the gvt global gtt oos lists.
  - vgpu_lock protects per-vGPU data and logic, especially the vGPU
    trap emulation path.
  - sched_lock protects gvt scheudler structure, context schedule logic
    and vGPU's schedule data.

GVT gtt contains 2 oos list, and one global mm list. Use a special
gvt->gtt_lock to protect those 3 lists.

v4:
  - Rebase to latest gvt-staging.
  - Add missing protection when access list in clean_spt_oos().
  - Fix locked recursive call of detach_oos_page when cleanup. (zhenyu)
v3: Update to latest code base.
v2: use gtt_lock to cover correct scope in ppgtt_allocate_oos_page().

Performance comparison on Kabylake platform.
  - Configuration:
    Host: Ubuntu 16.04.
    Guest 1 & 2: Ubuntu 16.04.

glmark2 score comparison:
  - Configuration:
    Host: glxgears.
    Guests: glmark2.
+--------------------------------+-----------------+
| Setup                          | glmark2 score   |
+--------------------------------+-----------------+
| unified lock, iommu=on         | 58~62 (avg. 60) |
+--------------------------------+-----------------+
| unified lock, iommu=igfx_off   | 57~61 (avg. 59) |
+--------------------------------+-----------------+
| per-logic lock, iommu=on       | 60~68 (avg. 64) |
+--------------------------------+-----------------+
| per-logic lock, iommu=igfx_off | 61~67 (avg. 64) |
+--------------------------------+-----------------+

lock_stat comparison:
  - Configuration:
    Stop lock stat immediately after boot up.
    Boot 2 VM Guests.
    Run glmark2 in guests.
    Start perf lock_stat for 20 seconds and stop again.
  - Legend: c - contentions; w - waittime-avg
+------------+-----------------+-----------+---------------+------------+
|            | gvt_lock        |sched_lock | vgpu_lock     | gtt_lock   |
+ lock type; +-----------------+-----------+---------------+------------+
| iommu set  | c     | w       | c  | w    | c    | w      | c   | w    |
+------------+-------+---------+----+------+------+--------+-----+------+
| unified;   | 20697 | 839     |N/A | N/A  | N/A  | N/A    | N/A | N/A  |
| on         |       |         |    |      |      |        |     |      |
+------------+-------+---------+----+------+------+--------+-----+------+
| unified;   | 21838 | 658.15  |N/A | N/A  | N/A  | N/A    | N/A | N/A  |
| igfx_off   |       |         |    |      |      |        |     |      |
+------------+-------+---------+----+------+------+--------+-----+------+
| per-logic; | 1553  | 1599.96 |9458|429.97| 5846 | 274.33 | 0   | 0.00 |
| on         |       |         |    |      |      |        |     |      |
+------------+-------+---------+----+------+------+--------+-----+------+
| per-logic; | 1911  | 1678.32 |8335|445.16| 5451 | 244.80 | 0   | 0.00 |
| igfx_off   |       |         |    |      |      |        |     |      |
+------------+-------+---------+----+------+------+--------+-----+------+

Signed-off-by: Pei Zhang <pei.zhang at intel.com>
Signed-off-by: Colin Xu <colin.xu at intel.com>
---
 drivers/gpu/drm/i915/gvt/gtt.c | 38 +++++++++++++++++++++++++++-----------
 drivers/gpu/drm/i915/gvt/gvt.c |  1 +
 drivers/gpu/drm/i915/gvt/gvt.h |  2 ++
 3 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/i915/gvt/gtt.c b/drivers/gpu/drm/i915/gvt/gtt.c
index 78e55aafc8bc..f78b4b9c10a8 100644
--- a/drivers/gpu/drm/i915/gvt/gtt.c
+++ b/drivers/gpu/drm/i915/gvt/gtt.c
@@ -639,7 +639,7 @@ static void free_spt(struct intel_vgpu_ppgtt_spt *spt)
 	kfree(spt);
 }
 
-static int detach_oos_page(struct intel_vgpu *vgpu,
+static int detach_oos_page_locked(struct intel_vgpu *vgpu,
 		struct intel_vgpu_oos_page *oos_page);
 
 static void ppgtt_free_spt(struct intel_vgpu_ppgtt_spt *spt)
@@ -653,8 +653,11 @@ static void ppgtt_free_spt(struct intel_vgpu_ppgtt_spt *spt)
 
 	radix_tree_delete(&spt->vgpu->gtt.spt_tree, spt->shadow_page.mfn);
 
-	if (spt->guest_page.oos_page)
-		detach_oos_page(spt->vgpu, spt->guest_page.oos_page);
+	if (spt->guest_page.oos_page) {
+		mutex_lock(&spt->vgpu->gvt->gtt_lock);
+		detach_oos_page_locked(spt->vgpu, spt->guest_page.oos_page);
+		mutex_unlock(&spt->vgpu->gvt->gtt_lock);
+	}
 
 	intel_vgpu_unregister_page_track(spt->vgpu, spt->guest_page.gfn);
 
@@ -1150,7 +1153,7 @@ static int sync_oos_page(struct intel_vgpu *vgpu,
 	return 0;
 }
 
-static int detach_oos_page(struct intel_vgpu *vgpu,
+static int detach_oos_page_locked(struct intel_vgpu *vgpu,
 		struct intel_vgpu_oos_page *oos_page)
 {
 	struct intel_gvt *gvt = vgpu->gvt;
@@ -1169,7 +1172,7 @@ static int detach_oos_page(struct intel_vgpu *vgpu,
 	return 0;
 }
 
-static int attach_oos_page(struct intel_vgpu_oos_page *oos_page,
+static int attach_oos_page_locked(struct intel_vgpu_oos_page *oos_page,
 		struct intel_vgpu_ppgtt_spt *spt)
 {
 	struct intel_gvt *gvt = spt->vgpu->gvt;
@@ -1216,19 +1219,23 @@ static int ppgtt_allocate_oos_page(struct intel_vgpu_ppgtt_spt *spt)
 
 	WARN(oos_page, "shadow PPGTT page has already has a oos page\n");
 
+	mutex_lock(&gvt->gtt_lock);
 	if (list_empty(&gtt->oos_page_free_list_head)) {
 		oos_page = container_of(gtt->oos_page_use_list_head.next,
 			struct intel_vgpu_oos_page, list);
 		ret = ppgtt_set_guest_page_sync(oos_page->spt);
 		if (ret)
-			return ret;
-		ret = detach_oos_page(spt->vgpu, oos_page);
+			goto out;
+		ret = detach_oos_page_locked(spt->vgpu, oos_page);
 		if (ret)
-			return ret;
+			goto out;
 	} else
 		oos_page = container_of(gtt->oos_page_free_list_head.next,
 			struct intel_vgpu_oos_page, list);
-	return attach_oos_page(oos_page, spt);
+	ret = attach_oos_page_locked(oos_page, spt);
+out:
+	mutex_unlock(&gvt->gtt_lock);
+	return ret;
 }
 
 static int ppgtt_set_guest_page_oos(struct intel_vgpu_ppgtt_spt *spt)
@@ -1653,8 +1660,10 @@ int intel_vgpu_pin_mm(struct intel_vgpu_mm *mm)
 		if (ret)
 			return ret;
 
+		mutex_lock(&mm->vgpu->gvt->gtt_lock);
 		list_move_tail(&mm->ppgtt_mm.lru_list,
 			       &mm->vgpu->gvt->gtt.ppgtt_mm_lru_list_head);
+		mutex_unlock(&mm->vgpu->gvt->gtt_lock);
 
 	}
 
@@ -1663,9 +1672,11 @@ int intel_vgpu_pin_mm(struct intel_vgpu_mm *mm)
 
 static int reclaim_one_ppgtt_mm(struct intel_gvt *gvt)
 {
+	int ret = 0;
 	struct intel_vgpu_mm *mm;
 	struct list_head *pos, *n;
 
+	mutex_lock(&gvt->gtt_lock);
 	list_for_each_safe(pos, n, &gvt->gtt.ppgtt_mm_lru_list_head) {
 		mm = container_of(pos, struct intel_vgpu_mm, ppgtt_mm.lru_list);
 
@@ -1674,9 +1685,11 @@ static int reclaim_one_ppgtt_mm(struct intel_gvt *gvt)
 
 		list_del_init(&mm->ppgtt_mm.lru_list);
 		invalidate_ppgtt_mm(mm);
-		return 1;
+		ret = 1;
 	}
-	return 0;
+	mutex_unlock(&gvt->gtt_lock);
+
+	return ret;
 }
 
 /*
@@ -2109,6 +2122,8 @@ static void clean_spt_oos(struct intel_gvt *gvt)
 	struct list_head *pos, *n;
 	struct intel_vgpu_oos_page *oos_page;
 
+	mutex_lock(&gvt->gtt_lock);
+
 	WARN(!list_empty(&gtt->oos_page_use_list_head),
 		"someone is still using oos page\n");
 
@@ -2117,6 +2132,7 @@ static void clean_spt_oos(struct intel_gvt *gvt)
 		list_del(&oos_page->list);
 		kfree(oos_page);
 	}
+	mutex_unlock(&gvt->gtt_lock);
 }
 
 static int setup_spt_oos(struct intel_gvt *gvt)
diff --git a/drivers/gpu/drm/i915/gvt/gvt.c b/drivers/gpu/drm/i915/gvt/gvt.c
index 61bd14fcb649..91c37f115780 100644
--- a/drivers/gpu/drm/i915/gvt/gvt.c
+++ b/drivers/gpu/drm/i915/gvt/gvt.c
@@ -379,6 +379,7 @@ int intel_gvt_init_device(struct drm_i915_private *dev_priv)
 	idr_init(&gvt->vgpu_idr);
 	spin_lock_init(&gvt->scheduler.mmio_context_lock);
 	mutex_init(&gvt->lock);
+	mutex_init(&gvt->gtt_lock);
 	gvt->dev_priv = dev_priv;
 
 	init_device_info(gvt);
diff --git a/drivers/gpu/drm/i915/gvt/gvt.h b/drivers/gpu/drm/i915/gvt/gvt.h
index efacd8abbedc..01fe294eab74 100644
--- a/drivers/gpu/drm/i915/gvt/gvt.h
+++ b/drivers/gpu/drm/i915/gvt/gvt.h
@@ -295,6 +295,8 @@ struct intel_vgpu_type {
 
 struct intel_gvt {
 	struct mutex lock;
+	struct mutex gtt_lock;
+
 	struct drm_i915_private *dev_priv;
 	struct idr vgpu_idr;	/* vGPU IDR pool */
 
-- 
2.16.3



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