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Commit ab7a2375 authored by Cornelia Huck's avatar Cornelia Huck Committed by Michael S. Tsirkin
Browse files

virtio: hint if callbacks surprisingly might sleep 



A virtio transport is free to implement some of the callbacks in
virtio_config_ops in a matter that they cannot be called from
atomic context (e.g. virtio-ccw, which maps a lot of the callbacks
to channel I/O, which is an inherently asynchronous mechanism).
This can be very surprising for developers using the much more
common virtio-pci transport, just to find out that things break
when used on s390.

The documentation for virtio_config_ops now contains a comment
explaining this, but it makes sense to add a might_sleep() annotation
to various wrapper functions in the virtio core to avoid surprises
later.

Note that annotations are NOT added to two classes of calls:
- direct calls from device drivers (all current callers should be
  fine, however)
- calls which clearly won't be made from atomic context (such as
  those ultimately coming in via the driver core)

Signed-off-by: default avatarCornelia Huck <cohuck@redhat.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 971bedca

drivers/virtio/virtio.c

+2 −0
Original line number Diff line number Diff line
@@ -161,6 +161,7 @@ EXPORT_SYMBOL_GPL(virtio_config_enable); 


void virtio_add_status(struct virtio_device *dev, unsigned int status)

{

	might_sleep();

	dev->config->set_status(dev, dev->config->get_status(dev) | status);

}

EXPORT_SYMBOL_GPL(virtio_add_status);
@@ -170,6 +171,7 @@ int virtio_finalize_features(struct virtio_device *dev) 
	int ret = dev->config->finalize_features(dev);

	unsigned status;



	might_sleep();

	if (ret)

		return ret;

include/linux/virtio_config.h

+13 −0
Original line number Diff line number Diff line
@@ -290,6 +290,7 @@ static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val) 
/* Config space accessors. */

#define virtio_cread(vdev, structname, member, ptr)			\

	do {								\

		might_sleep();						\

		/* Must match the member's type, and be integer */	\

		if (!typecheck(typeof((((structname*)0)->member)), *(ptr))) \

			(*ptr) = 1;					\
@@ -319,6 +320,7 @@ static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val) 
/* Config space accessors. */

#define virtio_cwrite(vdev, structname, member, ptr)			\

	do {								\

		might_sleep();						\

		/* Must match the member's type, and be integer */	\

		if (!typecheck(typeof((((structname*)0)->member)), *(ptr))) \

			BUG_ON((*ptr) == 1);				\
@@ -358,6 +360,7 @@ static inline void __virtio_cread_many(struct virtio_device *vdev, 
		vdev->config->generation(vdev) : 0;

	int i;



	might_sleep();

	do {

		old = gen;
@@ -380,6 +383,8 @@ static inline void virtio_cread_bytes(struct virtio_device *vdev, 
static inline u8 virtio_cread8(struct virtio_device *vdev, unsigned int offset)

{

	u8 ret;



	might_sleep();

	vdev->config->get(vdev, offset, &ret, sizeof(ret));

	return ret;

}
@@ -387,6 +392,7 @@ static inline u8 virtio_cread8(struct virtio_device *vdev, unsigned int offset) 
static inline void virtio_cwrite8(struct virtio_device *vdev,

				  unsigned int offset, u8 val)

{

	might_sleep();

	vdev->config->set(vdev, offset, &val, sizeof(val));

}
@@ -394,6 +400,8 @@ static inline u16 virtio_cread16(struct virtio_device *vdev, 
				 unsigned int offset)

{

	u16 ret;



	might_sleep();

	vdev->config->get(vdev, offset, &ret, sizeof(ret));

	return virtio16_to_cpu(vdev, (__force __virtio16)ret);

}
@@ -401,6 +409,7 @@ static inline u16 virtio_cread16(struct virtio_device *vdev, 
static inline void virtio_cwrite16(struct virtio_device *vdev,

				   unsigned int offset, u16 val)

{

	might_sleep();

	val = (__force u16)cpu_to_virtio16(vdev, val);

	vdev->config->set(vdev, offset, &val, sizeof(val));

}
@@ -409,6 +418,8 @@ static inline u32 virtio_cread32(struct virtio_device *vdev, 
				 unsigned int offset)

{

	u32 ret;



	might_sleep();

	vdev->config->get(vdev, offset, &ret, sizeof(ret));

	return virtio32_to_cpu(vdev, (__force __virtio32)ret);

}
@@ -416,6 +427,7 @@ static inline u32 virtio_cread32(struct virtio_device *vdev, 
static inline void virtio_cwrite32(struct virtio_device *vdev,

				   unsigned int offset, u32 val)

{

	might_sleep();

	val = (__force u32)cpu_to_virtio32(vdev, val);

	vdev->config->set(vdev, offset, &val, sizeof(val));

}
@@ -431,6 +443,7 @@ static inline u64 virtio_cread64(struct virtio_device *vdev, 
static inline void virtio_cwrite64(struct virtio_device *vdev,

				   unsigned int offset, u64 val)

{

	might_sleep();

	val = (__force u64)cpu_to_virtio64(vdev, val);

	vdev->config->set(vdev, offset, &val, sizeof(val));

}