[PATCH v5 1/3] drm/i915/gvt: Use gtt_lock to protect gtt list

[colin.xu at intel.com]

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.

v5:
  - Rebase to latest gvt-staging.
  - gtt access is already protected by vgpu_lock, so gtt_lock is
    unnecessary currently. Will keep for init/clean for further usage.
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 | 7 +++++++
 drivers/gpu/drm/i915/gvt/gvt.c | 1 +
 drivers/gpu/drm/i915/gvt/gvt.h | 2 ++
 3 files changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/i915/gvt/gtt.c b/drivers/gpu/drm/i915/gvt/gtt.c
index 78e55aafc8bc..9ad3b8105e73 100644
--- a/drivers/gpu/drm/i915/gvt/gtt.c
+++ b/drivers/gpu/drm/i915/gvt/gtt.c
@@ -2109,6 +2109,8 @@ 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 +2119,7 @@ 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)
@@ -2126,6 +2129,8 @@ static int setup_spt_oos(struct intel_gvt *gvt)
 	int i;
 	int ret;
 
+	mutex_lock(&gvt->gtt_lock);
+
 	INIT_LIST_HEAD(&gtt->oos_page_free_list_head);
 	INIT_LIST_HEAD(&gtt->oos_page_use_list_head);
 
@@ -2142,6 +2147,8 @@ static int setup_spt_oos(struct intel_gvt *gvt)
 		list_add_tail(&oos_page->list, &gtt->oos_page_free_list_head);
 	}
 
+	mutex_unlock(&gvt->gtt_lock);
+
 	gvt_dbg_mm("%d oos pages preallocated\n", i);
 
 	return 0;
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