[PATCH 1/3] drm/vmwgfx: Drop svga_lock

[PATCH 1/3] drm/vmwgfx: Drop svga_lock

[Daniel Vetter]

This isn't actually protecting anything becuase:
- when running, ttm_resource_manager->use_type is protected through
  vmw_private->reservation_semaphore against concurrent execbuf or
  well anything else that might evict or reserve buffers
- during suspend/resume there's nothing else running, hence
  vmw_pm_freeze and vmw_pm_restore do not need to take the same lock.
- this also holds for the SVGA_REG_ENABLE register write

Hence it is safe to just remove that spinlock.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
Cc: Roland Scheidegger <sroland@vmware.com>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_drv.c | 10 +---------
 drivers/gpu/drm/vmwgfx/vmwgfx_drv.h |  1 -
 2 files changed, 1 insertion(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
index 0008be02d31c..204f7a1830f0 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
@@ -672,7 +672,6 @@ static int vmw_driver_load(struct drm_device *dev, unsigned long chipset)
 	spin_lock_init(&dev_priv->hw_lock);
 	spin_lock_init(&dev_priv->waiter_lock);
 	spin_lock_init(&dev_priv->cap_lock);
-	spin_lock_init(&dev_priv->svga_lock);
 	spin_lock_init(&dev_priv->cursor_lock);
 
 	for (i = vmw_res_context; i < vmw_res_max; ++i) {
@@ -1189,12 +1188,10 @@ static void __vmw_svga_enable(struct vmw_private *dev_priv)
 {
 	struct ttm_resource_manager *man = ttm_manager_type(&dev_priv->bdev, TTM_PL_VRAM);
 
-	spin_lock(&dev_priv->svga_lock);
 	if (!ttm_resource_manager_used(man)) {
 		vmw_write(dev_priv, SVGA_REG_ENABLE, SVGA_REG_ENABLE);
 		ttm_resource_manager_set_used(man, true);
 	}
-	spin_unlock(&dev_priv->svga_lock);
 }
 
 /**
@@ -1220,14 +1217,12 @@ static void __vmw_svga_disable(struct vmw_private *dev_priv)
 {
 	struct ttm_resource_manager *man = ttm_manager_type(&dev_priv->bdev, TTM_PL_VRAM);
 
-	spin_lock(&dev_priv->svga_lock);
 	if (ttm_resource_manager_used(man)) {
 		ttm_resource_manager_set_used(man, false);
 		vmw_write(dev_priv, SVGA_REG_ENABLE,
 			  SVGA_REG_ENABLE_HIDE |
 			  SVGA_REG_ENABLE_ENABLE);
 	}
-	spin_unlock(&dev_priv->svga_lock);
 }
 
 /**
@@ -1254,17 +1249,14 @@ void vmw_svga_disable(struct vmw_private *dev_priv)
 	 */
 	vmw_kms_lost_device(dev_priv->dev);
 	ttm_write_lock(&dev_priv->reservation_sem, false);
-	spin_lock(&dev_priv->svga_lock);
 	if (ttm_resource_manager_used(man)) {
 		ttm_resource_manager_set_used(man, false);
-		spin_unlock(&dev_priv->svga_lock);
 		if (ttm_resource_manager_evict_all(&dev_priv->bdev, man))
 			DRM_ERROR("Failed evicting VRAM buffers.\n");
 		vmw_write(dev_priv, SVGA_REG_ENABLE,
 			  SVGA_REG_ENABLE_HIDE |
 			  SVGA_REG_ENABLE_ENABLE);
-	} else
-		spin_unlock(&dev_priv->svga_lock);
+	}
 	ttm_write_unlock(&dev_priv->reservation_sem);
 }
 
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
index 5b9a28157dd3..715f2bfee08a 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
@@ -596,7 +596,6 @@ struct vmw_private {
 
 	bool stealth;
 	bool enable_fb;
-	spinlock_t svga_lock;
 
 	/**
 	 * PM management.
-- 
2.29.2

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[PATCH 2/3] drm/vmwgfx: Always evict vram _before_ disabling it

[Daniel Vetter]

Other way round is a bit inconsistent (but not buggy in any kind).
This is prep work so that ttm_resource_manager_set_used can assert
that the resource manager is empty.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
Cc: Roland Scheidegger <sroland@vmware.com>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_drv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
index 204f7a1830f0..0d074c432152 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
@@ -1250,9 +1250,9 @@ void vmw_svga_disable(struct vmw_private *dev_priv)
 	vmw_kms_lost_device(dev_priv->dev);
 	ttm_write_lock(&dev_priv->reservation_sem, false);
 	if (ttm_resource_manager_used(man)) {
-		ttm_resource_manager_set_used(man, false);
 		if (ttm_resource_manager_evict_all(&dev_priv->bdev, man))
 			DRM_ERROR("Failed evicting VRAM buffers.\n");
+		ttm_resource_manager_set_used(man, false);
 		vmw_write(dev_priv, SVGA_REG_ENABLE,
 			  SVGA_REG_ENABLE_HIDE |
 			  SVGA_REG_ENABLE_ENABLE);
-- 
2.29.2

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[PATCH 3/3] drm/ttm: WARN_ON non-empty lru when disabling a resource manager

[Daniel Vetter]

ttm_resource_manager->use_type is only used for runtime changes by
vmwgfx. I think ideally we'd push this functionality into drivers -
ttm itself does not provide any locking to guarantee this is safe, so
the only way this can work at runtime is if the driver does provide
additional guarantees. vwmgfx does that through the
vmw_private->reservation_sem. Therefore supporting this feature in
shared code feels a bit misplaced.

As a first step add a WARN_ON to make sure the resource manager is
empty. This is just to make sure I actually understand correctly what
vmwgfx is doing, and to make sure an eventual subsequent refactor
doesn't break anything.

This check should also be useful for other drivers, to make sure they
haven't leaked anything.

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Christian Koenig <christian.koenig@amd.com>
Cc: Huang Rui <ray.huang@amd.com>
---
 include/drm/ttm/ttm_resource.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/drm/ttm/ttm_resource.h b/include/drm/ttm/ttm_resource.h
index f48a70d39ac5..789ec477b607 100644
--- a/include/drm/ttm/ttm_resource.h
+++ b/include/drm/ttm/ttm_resource.h
@@ -191,6 +191,10 @@ struct ttm_resource {
 static inline void
 ttm_resource_manager_set_used(struct ttm_resource_manager *man, bool used)
 {
+	int i;
+
+	for (i = 0; i < TTM_MAX_BO_PRIORITY; i++)
+		WARN_ON(!list_empty(&man->lru[i]));
 	man->use_type = used;
 }
 
-- 
2.29.2

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Re: [PATCH 1/3] drm/vmwgfx: Drop svga_lock

[Daniel Vetter]

Hi Roland,

Hopefully you had a nice start into the new year! Ping for some
review/testing on this series.

Thanks, Daniel

On Fri, Dec 11, 2020 at 5:29 PM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>
> This isn't actually protecting anything becuase:
> - when running, ttm_resource_manager->use_type is protected through
>   vmw_private->reservation_semaphore against concurrent execbuf or
>   well anything else that might evict or reserve buffers
> - during suspend/resume there's nothing else running, hence
>   vmw_pm_freeze and vmw_pm_restore do not need to take the same lock.
> - this also holds for the SVGA_REG_ENABLE register write
>
> Hence it is safe to just remove that spinlock.
>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
> Cc: Roland Scheidegger <sroland@vmware.com>
> ---
>  drivers/gpu/drm/vmwgfx/vmwgfx_drv.c | 10 +---------
>  drivers/gpu/drm/vmwgfx/vmwgfx_drv.h |  1 -
>  2 files changed, 1 insertion(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> index 0008be02d31c..204f7a1830f0 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> @@ -672,7 +672,6 @@ static int vmw_driver_load(struct drm_device *dev, unsigned long chipset)
>         spin_lock_init(&dev_priv->hw_lock);
>         spin_lock_init(&dev_priv->waiter_lock);
>         spin_lock_init(&dev_priv->cap_lock);
> -       spin_lock_init(&dev_priv->svga_lock);
>         spin_lock_init(&dev_priv->cursor_lock);
>
>         for (i = vmw_res_context; i < vmw_res_max; ++i) {
> @@ -1189,12 +1188,10 @@ static void __vmw_svga_enable(struct vmw_private *dev_priv)
>  {
>         struct ttm_resource_manager *man = ttm_manager_type(&dev_priv->bdev, TTM_PL_VRAM);
>
> -       spin_lock(&dev_priv->svga_lock);
>         if (!ttm_resource_manager_used(man)) {
>                 vmw_write(dev_priv, SVGA_REG_ENABLE, SVGA_REG_ENABLE);
>                 ttm_resource_manager_set_used(man, true);
>         }
> -       spin_unlock(&dev_priv->svga_lock);
>  }
>
>  /**
> @@ -1220,14 +1217,12 @@ static void __vmw_svga_disable(struct vmw_private *dev_priv)
>  {
>         struct ttm_resource_manager *man = ttm_manager_type(&dev_priv->bdev, TTM_PL_VRAM);
>
> -       spin_lock(&dev_priv->svga_lock);
>         if (ttm_resource_manager_used(man)) {
>                 ttm_resource_manager_set_used(man, false);
>                 vmw_write(dev_priv, SVGA_REG_ENABLE,
>                           SVGA_REG_ENABLE_HIDE |
>                           SVGA_REG_ENABLE_ENABLE);
>         }
> -       spin_unlock(&dev_priv->svga_lock);
>  }
>
>  /**
> @@ -1254,17 +1249,14 @@ void vmw_svga_disable(struct vmw_private *dev_priv)
>          */
>         vmw_kms_lost_device(dev_priv->dev);
>         ttm_write_lock(&dev_priv->reservation_sem, false);
> -       spin_lock(&dev_priv->svga_lock);
>         if (ttm_resource_manager_used(man)) {
>                 ttm_resource_manager_set_used(man, false);
> -               spin_unlock(&dev_priv->svga_lock);
>                 if (ttm_resource_manager_evict_all(&dev_priv->bdev, man))
>                         DRM_ERROR("Failed evicting VRAM buffers.\n");
>                 vmw_write(dev_priv, SVGA_REG_ENABLE,
>                           SVGA_REG_ENABLE_HIDE |
>                           SVGA_REG_ENABLE_ENABLE);
> -       } else
> -               spin_unlock(&dev_priv->svga_lock);
> +       }
>         ttm_write_unlock(&dev_priv->reservation_sem);
>  }
>
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> index 5b9a28157dd3..715f2bfee08a 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> @@ -596,7 +596,6 @@ struct vmw_private {
>
>         bool stealth;
>         bool enable_fb;
> -       spinlock_t svga_lock;
>
>         /**
>          * PM management.
> --
> 2.29.2
>


-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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Re: [PATCH 1/3] drm/vmwgfx: Drop svga_lock

[Zack Rusin]

Looks good. Thanks!

Reviewed-by: Zack Rusin <zackr@vmware.com>

> On Jan 12, 2021, at 03:49, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> 
> Hi Roland,
> 
> Hopefully you had a nice start into the new year! Ping for some
> review/testing on this series.
> 
> Thanks, Daniel
> 
> On Fri, Dec 11, 2020 at 5:29 PM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>> 
>> This isn't actually protecting anything becuase:
>> - when running, ttm_resource_manager->use_type is protected through
>>  vmw_private->reservation_semaphore against concurrent execbuf or
>>  well anything else that might evict or reserve buffers
>> - during suspend/resume there's nothing else running, hence
>>  vmw_pm_freeze and vmw_pm_restore do not need to take the same lock.
>> - this also holds for the SVGA_REG_ENABLE register write
>> 
>> Hence it is safe to just remove that spinlock.
>> 
>> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
>> Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
>> Cc: Roland Scheidegger <sroland@vmware.com>
>> ---
>> drivers/gpu/drm/vmwgfx/vmwgfx_drv.c | 10 +---------
>> drivers/gpu/drm/vmwgfx/vmwgfx_drv.h |  1 -
>> 2 files changed, 1 insertion(+), 10 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
>> index 0008be02d31c..204f7a1830f0 100644
>> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
>> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
>> @@ -672,7 +672,6 @@ static int vmw_driver_load(struct drm_device *dev, unsigned long chipset)
>>        spin_lock_init(&dev_priv->hw_lock);
>>        spin_lock_init(&dev_priv->waiter_lock);
>>        spin_lock_init(&dev_priv->cap_lock);
>> -       spin_lock_init(&dev_priv->svga_lock);
>>        spin_lock_init(&dev_priv->cursor_lock);
>> 
>>        for (i = vmw_res_context; i < vmw_res_max; ++i) {
>> @@ -1189,12 +1188,10 @@ static void __vmw_svga_enable(struct vmw_private *dev_priv)
>> {
>>        struct ttm_resource_manager *man = ttm_manager_type(&dev_priv->bdev, TTM_PL_VRAM);
>> 
>> -       spin_lock(&dev_priv->svga_lock);
>>        if (!ttm_resource_manager_used(man)) {
>>                vmw_write(dev_priv, SVGA_REG_ENABLE, SVGA_REG_ENABLE);
>>                ttm_resource_manager_set_used(man, true);
>>        }
>> -       spin_unlock(&dev_priv->svga_lock);
>> }
>> 
>> /**
>> @@ -1220,14 +1217,12 @@ static void __vmw_svga_disable(struct vmw_private *dev_priv)
>> {
>>        struct ttm_resource_manager *man = ttm_manager_type(&dev_priv->bdev, TTM_PL_VRAM);
>> 
>> -       spin_lock(&dev_priv->svga_lock);
>>        if (ttm_resource_manager_used(man)) {
>>                ttm_resource_manager_set_used(man, false);
>>                vmw_write(dev_priv, SVGA_REG_ENABLE,
>>                          SVGA_REG_ENABLE_HIDE |
>>                          SVGA_REG_ENABLE_ENABLE);
>>        }
>> -       spin_unlock(&dev_priv->svga_lock);
>> }
>> 
>> /**
>> @@ -1254,17 +1249,14 @@ void vmw_svga_disable(struct vmw_private *dev_priv)
>>         */
>>        vmw_kms_lost_device(dev_priv->dev);
>>        ttm_write_lock(&dev_priv->reservation_sem, false);
>> -       spin_lock(&dev_priv->svga_lock);
>>        if (ttm_resource_manager_used(man)) {
>>                ttm_resource_manager_set_used(man, false);
>> -               spin_unlock(&dev_priv->svga_lock);
>>                if (ttm_resource_manager_evict_all(&dev_priv->bdev, man))
>>                        DRM_ERROR("Failed evicting VRAM buffers.\n");
>>                vmw_write(dev_priv, SVGA_REG_ENABLE,
>>                          SVGA_REG_ENABLE_HIDE |
>>                          SVGA_REG_ENABLE_ENABLE);
>> -       } else
>> -               spin_unlock(&dev_priv->svga_lock);
>> +       }
>>        ttm_write_unlock(&dev_priv->reservation_sem);
>> }
>> 
>> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
>> index 5b9a28157dd3..715f2bfee08a 100644
>> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
>> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
>> @@ -596,7 +596,6 @@ struct vmw_private {
>> 
>>        bool stealth;
>>        bool enable_fb;
>> -       spinlock_t svga_lock;
>> 
>>        /**
>>         * PM management.
>> --
>> 2.29.2
>> 
> 
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> https://nam04.safelinks.protection.outlook.com/?url=http%3A%2F%2Fblog.ffwll.ch%2F&amp;data=04%7C01%7Czackr%40vmware.com%7C87dbfc543ea847f8e13808d8b6d6f273%7Cb39138ca3cee4b4aa4d6cd83d9dd62f0%7C0%7C0%7C637460381607335152%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=TttOwJzt5g8Sk45jqfa9qFkVCQrslhOmdjDyKQJzkIk%3D&amp;reserved=0

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Re: [PATCH 1/3] drm/vmwgfx: Drop svga_lock

[Roland Scheidegger]

Hi,

looking at it, seems alright. Not sure why the lock was supposedly
needed, maybe it was at some point (it seems like all usage of this lock
was introduced way back in 2015, commit 153b3d5b037ee).

For the series: Reviewed-by: Roland Scheidegger <sroland@vmware.com>

Roland

Am 12.01.21 um 09:49 schrieb Daniel Vetter:
> Hi Roland,
> 
> Hopefully you had a nice start into the new year! Ping for some
> review/testing on this series.
> 
> Thanks, Daniel
> 
> On Fri, Dec 11, 2020 at 5:29 PM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>>
>> This isn't actually protecting anything becuase:
>> - when running, ttm_resource_manager->use_type is protected through
>>   vmw_private->reservation_semaphore against concurrent execbuf or
>>   well anything else that might evict or reserve buffers
>> - during suspend/resume there's nothing else running, hence
>>   vmw_pm_freeze and vmw_pm_restore do not need to take the same lock.
>> - this also holds for the SVGA_REG_ENABLE register write
>>
>> Hence it is safe to just remove that spinlock.
>>
>> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
>> Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
>> Cc: Roland Scheidegger <sroland@vmware.com>
>> ---
>>  drivers/gpu/drm/vmwgfx/vmwgfx_drv.c | 10 +---------
>>  drivers/gpu/drm/vmwgfx/vmwgfx_drv.h |  1 -
>>  2 files changed, 1 insertion(+), 10 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
>> index 0008be02d31c..204f7a1830f0 100644
>> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
>> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
>> @@ -672,7 +672,6 @@ static int vmw_driver_load(struct drm_device *dev, unsigned long chipset)
>>         spin_lock_init(&dev_priv->hw_lock);
>>         spin_lock_init(&dev_priv->waiter_lock);
>>         spin_lock_init(&dev_priv->cap_lock);
>> -       spin_lock_init(&dev_priv->svga_lock);
>>         spin_lock_init(&dev_priv->cursor_lock);
>>
>>         for (i = vmw_res_context; i < vmw_res_max; ++i) {
>> @@ -1189,12 +1188,10 @@ static void __vmw_svga_enable(struct vmw_private *dev_priv)
>>  {
>>         struct ttm_resource_manager *man = ttm_manager_type(&dev_priv->bdev, TTM_PL_VRAM);
>>
>> -       spin_lock(&dev_priv->svga_lock);
>>         if (!ttm_resource_manager_used(man)) {
>>                 vmw_write(dev_priv, SVGA_REG_ENABLE, SVGA_REG_ENABLE);
>>                 ttm_resource_manager_set_used(man, true);
>>         }
>> -       spin_unlock(&dev_priv->svga_lock);
>>  }
>>
>>  /**
>> @@ -1220,14 +1217,12 @@ static void __vmw_svga_disable(struct vmw_private *dev_priv)
>>  {
>>         struct ttm_resource_manager *man = ttm_manager_type(&dev_priv->bdev, TTM_PL_VRAM);
>>
>> -       spin_lock(&dev_priv->svga_lock);
>>         if (ttm_resource_manager_used(man)) {
>>                 ttm_resource_manager_set_used(man, false);
>>                 vmw_write(dev_priv, SVGA_REG_ENABLE,
>>                           SVGA_REG_ENABLE_HIDE |
>>                           SVGA_REG_ENABLE_ENABLE);
>>         }
>> -       spin_unlock(&dev_priv->svga_lock);
>>  }
>>
>>  /**
>> @@ -1254,17 +1249,14 @@ void vmw_svga_disable(struct vmw_private *dev_priv)
>>          */
>>         vmw_kms_lost_device(dev_priv->dev);
>>         ttm_write_lock(&dev_priv->reservation_sem, false);
>> -       spin_lock(&dev_priv->svga_lock);
>>         if (ttm_resource_manager_used(man)) {
>>                 ttm_resource_manager_set_used(man, false);
>> -               spin_unlock(&dev_priv->svga_lock);
>>                 if (ttm_resource_manager_evict_all(&dev_priv->bdev, man))
>>                         DRM_ERROR("Failed evicting VRAM buffers.\n");
>>                 vmw_write(dev_priv, SVGA_REG_ENABLE,
>>                           SVGA_REG_ENABLE_HIDE |
>>                           SVGA_REG_ENABLE_ENABLE);
>> -       } else
>> -               spin_unlock(&dev_priv->svga_lock);
>> +       }
>>         ttm_write_unlock(&dev_priv->reservation_sem);
>>  }
>>
>> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
>> index 5b9a28157dd3..715f2bfee08a 100644
>> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
>> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
>> @@ -596,7 +596,6 @@ struct vmw_private {
>>
>>         bool stealth;
>>         bool enable_fb;
>> -       spinlock_t svga_lock;
>>
>>         /**
>>          * PM management.
>> --
>> 2.29.2
>>
> 
> 

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Re: [PATCH 1/3] drm/vmwgfx: Drop svga_lock

[Daniel Vetter]

On Thu, Jan 14, 2021 at 04:31:09PM +0100, Roland Scheidegger wrote:
> Hi,
> 
> looking at it, seems alright. Not sure why the lock was supposedly
> needed, maybe it was at some point (it seems like all usage of this lock
> was introduced way back in 2015, commit 153b3d5b037ee).
> 
> For the series: Reviewed-by: Roland Scheidegger <sroland@vmware.com>

Series merged, thanks for taking a look.
-Daniel

> 
> Roland
> 
> Am 12.01.21 um 09:49 schrieb Daniel Vetter:
> > Hi Roland,
> > 
> > Hopefully you had a nice start into the new year! Ping for some
> > review/testing on this series.
> > 
> > Thanks, Daniel
> > 
> > On Fri, Dec 11, 2020 at 5:29 PM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> >>
> >> This isn't actually protecting anything becuase:
> >> - when running, ttm_resource_manager->use_type is protected through
> >>   vmw_private->reservation_semaphore against concurrent execbuf or
> >>   well anything else that might evict or reserve buffers
> >> - during suspend/resume there's nothing else running, hence
> >>   vmw_pm_freeze and vmw_pm_restore do not need to take the same lock.
> >> - this also holds for the SVGA_REG_ENABLE register write
> >>
> >> Hence it is safe to just remove that spinlock.
> >>
> >> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> >> Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
> >> Cc: Roland Scheidegger <sroland@vmware.com>
> >> ---
> >>  drivers/gpu/drm/vmwgfx/vmwgfx_drv.c | 10 +---------
> >>  drivers/gpu/drm/vmwgfx/vmwgfx_drv.h |  1 -
> >>  2 files changed, 1 insertion(+), 10 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> >> index 0008be02d31c..204f7a1830f0 100644
> >> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> >> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> >> @@ -672,7 +672,6 @@ static int vmw_driver_load(struct drm_device *dev, unsigned long chipset)
> >>         spin_lock_init(&dev_priv->hw_lock);
> >>         spin_lock_init(&dev_priv->waiter_lock);
> >>         spin_lock_init(&dev_priv->cap_lock);
> >> -       spin_lock_init(&dev_priv->svga_lock);
> >>         spin_lock_init(&dev_priv->cursor_lock);
> >>
> >>         for (i = vmw_res_context; i < vmw_res_max; ++i) {
> >> @@ -1189,12 +1188,10 @@ static void __vmw_svga_enable(struct vmw_private *dev_priv)
> >>  {
> >>         struct ttm_resource_manager *man = ttm_manager_type(&dev_priv->bdev, TTM_PL_VRAM);
> >>
> >> -       spin_lock(&dev_priv->svga_lock);
> >>         if (!ttm_resource_manager_used(man)) {
> >>                 vmw_write(dev_priv, SVGA_REG_ENABLE, SVGA_REG_ENABLE);
> >>                 ttm_resource_manager_set_used(man, true);
> >>         }
> >> -       spin_unlock(&dev_priv->svga_lock);
> >>  }
> >>
> >>  /**
> >> @@ -1220,14 +1217,12 @@ static void __vmw_svga_disable(struct vmw_private *dev_priv)
> >>  {
> >>         struct ttm_resource_manager *man = ttm_manager_type(&dev_priv->bdev, TTM_PL_VRAM);
> >>
> >> -       spin_lock(&dev_priv->svga_lock);
> >>         if (ttm_resource_manager_used(man)) {
> >>                 ttm_resource_manager_set_used(man, false);
> >>                 vmw_write(dev_priv, SVGA_REG_ENABLE,
> >>                           SVGA_REG_ENABLE_HIDE |
> >>                           SVGA_REG_ENABLE_ENABLE);
> >>         }
> >> -       spin_unlock(&dev_priv->svga_lock);
> >>  }
> >>
> >>  /**
> >> @@ -1254,17 +1249,14 @@ void vmw_svga_disable(struct vmw_private *dev_priv)
> >>          */
> >>         vmw_kms_lost_device(dev_priv->dev);
> >>         ttm_write_lock(&dev_priv->reservation_sem, false);
> >> -       spin_lock(&dev_priv->svga_lock);
> >>         if (ttm_resource_manager_used(man)) {
> >>                 ttm_resource_manager_set_used(man, false);
> >> -               spin_unlock(&dev_priv->svga_lock);
> >>                 if (ttm_resource_manager_evict_all(&dev_priv->bdev, man))
> >>                         DRM_ERROR("Failed evicting VRAM buffers.\n");
> >>                 vmw_write(dev_priv, SVGA_REG_ENABLE,
> >>                           SVGA_REG_ENABLE_HIDE |
> >>                           SVGA_REG_ENABLE_ENABLE);
> >> -       } else
> >> -               spin_unlock(&dev_priv->svga_lock);
> >> +       }
> >>         ttm_write_unlock(&dev_priv->reservation_sem);
> >>  }
> >>
> >> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> >> index 5b9a28157dd3..715f2bfee08a 100644
> >> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> >> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> >> @@ -596,7 +596,6 @@ struct vmw_private {
> >>
> >>         bool stealth;
> >>         bool enable_fb;
> >> -       spinlock_t svga_lock;
> >>
> >>         /**
> >>          * PM management.
> >> --
> >> 2.29.2
> >>
> > 
> > 
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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