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virtio: hint if callbacks surprisingly might sleep

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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: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Cornelia Huck 2019-01-31 13:53:14 +01:00 committed by Michael S. Tsirkin
parent 971bedca26
commit ab7a2375fb
2 changed files with 15 additions and 0 deletions
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2
drivers/virtio/virtio.c
View File

@ -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;

13
include/linux/virtio_config.h
View File

@ -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));
}