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

Du, Changbin changbin.du at intel.com
Mon Apr 2 08:58:04 UTC 2018


On Sat, Mar 31, 2018 at 08:56:58AM +0800, Colin Xu wrote:
> 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   |       |         |    |      |      |        |     |      |
> +------------+-------+---------+----+------+------+--------+-----+------+
>
Colin,
Seeing above data, seems this new gtt_lock is not necessoray. The scope of
gtt_lock has already covered by gvt_lock. Because
intel_vgpu_page_track_handler() has acquired the gvt lock. Besides,
intel_vgpu_page_track_handler() should acquire vpu_lock instead of gvt_lock.
Thanks!

> 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
> 
> _______________________________________________
> intel-gvt-dev mailing list
> intel-gvt-dev at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gvt-dev

-- 
Thanks,
Changbin Du


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