Re: [PATCH v6 1/3] VFIO: Wrapper for getting reference to vfio_device from device

2013-03-04 Thread Alex Williamson 
On Sat, 2013-03-02 at 01:16 -0600, Vijay Mohan Pandarathil wrote:
>   - Added vfio_device_get_from_dev() as wrapper to get
>   reference to vfio_device from struct device.
> 
>   - Added vfio_device_data() as a wrapper to get device_data from
>   vfio_device.
> 
> Signed-off-by: Vijay Mohan Pandarathil 
> ---
>  drivers/vfio/vfio.c  | 27 ++-
>  include/linux/vfio.h |  3 +++
>  2 files changed, 29 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index 28e2d5b..eec6674 100644
> --- a/drivers/vfio/vfio.c
> +++ b/drivers/vfio/vfio.c
> @@ -407,12 +407,13 @@ static void vfio_device_release(struct kref *kref)
>  }
>  
>  /* Device reference always implies a group reference */
> -static void vfio_device_put(struct vfio_device *device)
> +void vfio_device_put(struct vfio_device *device)
>  {
>   struct vfio_group *group = device->group;
>   kref_put_mutex(>kref, vfio_device_release, >device_lock);
>   vfio_group_put(group);
>  }
> +EXPORT_SYMBOL_GPL(vfio_device_put);
>  
>  static void vfio_device_get(struct vfio_device *device)
>  {
> @@ -642,6 +643,30 @@ int vfio_add_group_dev(struct device *dev,
>  }
>  EXPORT_SYMBOL_GPL(vfio_add_group_dev);
>  
> +/**
> + * This does a get on the vfio_device from device.
> + * Callers of this function will have to call vfio_put_device() to
> + * remove the reference.
> + */

I think patch 2 is still racy, so let's try to improve this comment for
the next version as well.  The key is that the device is bound to a vfio
driver therefore the caller actually already has a reference to the
vfio_device.  Perhaps:

Get a reference to the vfio_device for a device that is known to
be bound to a vfio driver.  The driver implicitly holds a
vfio_device reference between vfio_add_group_dev and
vfio_del_group_dev.  We can therefore use drvdata to increment
that reference from the struct device.  This additional
reference must be released by calling vfio_device_put.

> +struct vfio_device *vfio_device_get_from_dev(struct device *dev)
> +{
> + struct vfio_device *device = dev_get_drvdata(dev);
> +
> + vfio_device_get(device);
> +
> + return device;
> +}
> +EXPORT_SYMBOL_GPL(vfio_device_get_from_dev);
> +
> +/*
> + * Caller must hold a reference to the vfio_device
> + */
> +void *vfio_device_data(struct vfio_device *device)
> +{
> + return device->device_data;
> +}
> +EXPORT_SYMBOL_GPL(vfio_device_data);
> +
>  /* Given a referenced group, check if it contains the device */
>  static bool vfio_dev_present(struct vfio_group *group, struct device *dev)
>  {
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index ab9e862..ac8d488 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -45,6 +45,9 @@ extern int vfio_add_group_dev(struct device *dev,
> void *device_data);
>  
>  extern void *vfio_del_group_dev(struct device *dev);
> +extern struct vfio_device *vfio_device_get_from_dev(struct device *dev);
> +extern void vfio_device_put(struct vfio_device *device);
> +extern void *vfio_device_data(struct vfio_device *device);
>  
>  /**
>   * struct vfio_iommu_driver_ops - VFIO IOMMU driver callbacks



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Re: [PATCH v6 1/3] VFIO: Wrapper for getting reference to vfio_device from device

2013-03-04 Thread Alex Williamson 
On Sat, 2013-03-02 at 01:16 -0600, Vijay Mohan Pandarathil wrote:
   - Added vfio_device_get_from_dev() as wrapper to get
   reference to vfio_device from struct device.
 
   - Added vfio_device_data() as a wrapper to get device_data from
   vfio_device.
 
 Signed-off-by: Vijay Mohan Pandarathil vijaymohan.pandarat...@hp.com
 ---
  drivers/vfio/vfio.c  | 27 ++-
  include/linux/vfio.h |  3 +++
  2 files changed, 29 insertions(+), 1 deletion(-)
 
 diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
 index 28e2d5b..eec6674 100644
 --- a/drivers/vfio/vfio.c
 +++ b/drivers/vfio/vfio.c
 @@ -407,12 +407,13 @@ static void vfio_device_release(struct kref *kref)
  }
  
  /* Device reference always implies a group reference */
 -static void vfio_device_put(struct vfio_device *device)
 +void vfio_device_put(struct vfio_device *device)
  {
   struct vfio_group *group = device-group;
   kref_put_mutex(device-kref, vfio_device_release, group-device_lock);
   vfio_group_put(group);
  }
 +EXPORT_SYMBOL_GPL(vfio_device_put);
  
  static void vfio_device_get(struct vfio_device *device)
  {
 @@ -642,6 +643,30 @@ int vfio_add_group_dev(struct device *dev,
  }
  EXPORT_SYMBOL_GPL(vfio_add_group_dev);
  
 +/**
 + * This does a get on the vfio_device from device.
 + * Callers of this function will have to call vfio_put_device() to
 + * remove the reference.
 + */

I think patch 2 is still racy, so let's try to improve this comment for
the next version as well.  The key is that the device is bound to a vfio
driver therefore the caller actually already has a reference to the
vfio_device.  Perhaps:

Get a reference to the vfio_device for a device that is known to
be bound to a vfio driver.  The driver implicitly holds a
vfio_device reference between vfio_add_group_dev and
vfio_del_group_dev.  We can therefore use drvdata to increment
that reference from the struct device.  This additional
reference must be released by calling vfio_device_put.

 +struct vfio_device *vfio_device_get_from_dev(struct device *dev)
 +{
 + struct vfio_device *device = dev_get_drvdata(dev);
 +
 + vfio_device_get(device);
 +
 + return device;
 +}
 +EXPORT_SYMBOL_GPL(vfio_device_get_from_dev);
 +
 +/*
 + * Caller must hold a reference to the vfio_device
 + */
 +void *vfio_device_data(struct vfio_device *device)
 +{
 + return device-device_data;
 +}
 +EXPORT_SYMBOL_GPL(vfio_device_data);
 +
  /* Given a referenced group, check if it contains the device */
  static bool vfio_dev_present(struct vfio_group *group, struct device *dev)
  {
 diff --git a/include/linux/vfio.h b/include/linux/vfio.h
 index ab9e862..ac8d488 100644
 --- a/include/linux/vfio.h
 +++ b/include/linux/vfio.h
 @@ -45,6 +45,9 @@ extern int vfio_add_group_dev(struct device *dev,
 void *device_data);
  
  extern void *vfio_del_group_dev(struct device *dev);
 +extern struct vfio_device *vfio_device_get_from_dev(struct device *dev);
 +extern void vfio_device_put(struct vfio_device *device);
 +extern void *vfio_device_data(struct vfio_device *device);
  
  /**
   * struct vfio_iommu_driver_ops - VFIO IOMMU driver callbacks



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[PATCH v6 1/3] VFIO: Wrapper for getting reference to vfio_device from device

2013-03-01 Thread Vijay Mohan Pandarathil 
- Added vfio_device_get_from_dev() as wrapper to get
  reference to vfio_device from struct device.

- Added vfio_device_data() as a wrapper to get device_data from
  vfio_device.

Signed-off-by: Vijay Mohan Pandarathil 
---
 drivers/vfio/vfio.c  | 27 ++-
 include/linux/vfio.h |  3 +++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 28e2d5b..eec6674 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -407,12 +407,13 @@ static void vfio_device_release(struct kref *kref)
 }
 
 /* Device reference always implies a group reference */
-static void vfio_device_put(struct vfio_device *device)
+void vfio_device_put(struct vfio_device *device)
 {
struct vfio_group *group = device->group;
kref_put_mutex(>kref, vfio_device_release, >device_lock);
vfio_group_put(group);
 }
+EXPORT_SYMBOL_GPL(vfio_device_put);
 
 static void vfio_device_get(struct vfio_device *device)
 {
@@ -642,6 +643,30 @@ int vfio_add_group_dev(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(vfio_add_group_dev);
 
+/**
+ * This does a get on the vfio_device from device.
+ * Callers of this function will have to call vfio_put_device() to
+ * remove the reference.
+ */
+struct vfio_device *vfio_device_get_from_dev(struct device *dev)
+{
+   struct vfio_device *device = dev_get_drvdata(dev);
+
+   vfio_device_get(device);
+
+   return device;
+}
+EXPORT_SYMBOL_GPL(vfio_device_get_from_dev);
+
+/*
+ * Caller must hold a reference to the vfio_device
+ */
+void *vfio_device_data(struct vfio_device *device)
+{
+   return device->device_data;
+}
+EXPORT_SYMBOL_GPL(vfio_device_data);
+
 /* Given a referenced group, check if it contains the device */
 static bool vfio_dev_present(struct vfio_group *group, struct device *dev)
 {
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index ab9e862..ac8d488 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -45,6 +45,9 @@ extern int vfio_add_group_dev(struct device *dev,
  void *device_data);
 
 extern void *vfio_del_group_dev(struct device *dev);
+extern struct vfio_device *vfio_device_get_from_dev(struct device *dev);
+extern void vfio_device_put(struct vfio_device *device);
+extern void *vfio_device_data(struct vfio_device *device);
 
 /**
  * struct vfio_iommu_driver_ops - VFIO IOMMU driver callbacks
-- 
1.7.11.3

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[PATCH v6 1/3] VFIO: Wrapper for getting reference to vfio_device from device

2013-03-01 Thread Vijay Mohan Pandarathil 
- Added vfio_device_get_from_dev() as wrapper to get
  reference to vfio_device from struct device.

- Added vfio_device_data() as a wrapper to get device_data from
  vfio_device.

Signed-off-by: Vijay Mohan Pandarathil vijaymohan.pandarat...@hp.com
---
 drivers/vfio/vfio.c  | 27 ++-
 include/linux/vfio.h |  3 +++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 28e2d5b..eec6674 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -407,12 +407,13 @@ static void vfio_device_release(struct kref *kref)
 }
 
 /* Device reference always implies a group reference */
-static void vfio_device_put(struct vfio_device *device)
+void vfio_device_put(struct vfio_device *device)
 {
struct vfio_group *group = device-group;
kref_put_mutex(device-kref, vfio_device_release, group-device_lock);
vfio_group_put(group);
 }
+EXPORT_SYMBOL_GPL(vfio_device_put);
 
 static void vfio_device_get(struct vfio_device *device)
 {
@@ -642,6 +643,30 @@ int vfio_add_group_dev(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(vfio_add_group_dev);
 
+/**
+ * This does a get on the vfio_device from device.
+ * Callers of this function will have to call vfio_put_device() to
+ * remove the reference.
+ */
+struct vfio_device *vfio_device_get_from_dev(struct device *dev)
+{
+   struct vfio_device *device = dev_get_drvdata(dev);
+
+   vfio_device_get(device);
+
+   return device;
+}
+EXPORT_SYMBOL_GPL(vfio_device_get_from_dev);
+
+/*
+ * Caller must hold a reference to the vfio_device
+ */
+void *vfio_device_data(struct vfio_device *device)
+{
+   return device-device_data;
+}
+EXPORT_SYMBOL_GPL(vfio_device_data);
+
 /* Given a referenced group, check if it contains the device */
 static bool vfio_dev_present(struct vfio_group *group, struct device *dev)
 {
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index ab9e862..ac8d488 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -45,6 +45,9 @@ extern int vfio_add_group_dev(struct device *dev,
  void *device_data);
 
 extern void *vfio_del_group_dev(struct device *dev);
+extern struct vfio_device *vfio_device_get_from_dev(struct device *dev);
+extern void vfio_device_put(struct vfio_device *device);
+extern void *vfio_device_data(struct vfio_device *device);
 
 /**
  * struct vfio_iommu_driver_ops - VFIO IOMMU driver callbacks
-- 
1.7.11.3

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