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virtio: core support for config generation 

virtio 1.0 spec says:

Drivers MUST NOT assume reads from fields greater than 32 bits wide are
atomic, nor are reads from multiple fields: drivers SHOULD read device
configuration space fields like so:
	u32 before, after;
	do {
		before = get_config_generation(device);
		// read config entry/entries.
		after = get_config_generation(device);
	} while (after != before);

Do exactly this, for transports that support it.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Michael S. Tsirkin 2014-12-14 16:55:44 +02:00
parent 0dce3771fd
commit d71de9ec6b
1 changed files with 28 additions and 4 deletions
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32
include/linux/virtio_config.h
View File

@ -19,6 +19,9 @@
* offset: the offset of the configuration field
* buf: the buffer to read the field value from.
* len: the length of the buffer
* @generation: config generation counter
* vdev: the virtio_device
* Returns the config generation counter
* @get_status: read the status byte
* vdev: the virtio_device
* Returns the status byte
@ -60,6 +63,7 @@ struct virtio_config_ops {
void *buf, unsigned len);
void (*set)(struct virtio_device *vdev, unsigned offset,
const void *buf, unsigned len);
u32 (*generation)(struct virtio_device *vdev);
u8 (*get_status)(struct virtio_device *vdev);
void (*set_status)(struct virtio_device *vdev, u8 status);
void (*reset)(struct virtio_device *vdev);
@ -301,14 +305,33 @@ static inline u8 virtio_cread8(struct virtio_device *vdev, unsigned int offset)
return ret;
}
/* Read @count fields, @bytes each. */
static inline void __virtio_cread_many(struct virtio_device *vdev,
unsigned int offset,
void *buf, size_t count, size_t bytes)
{
u32 old, gen = vdev->config->generation ?
vdev->config->generation(vdev) : 0;
int i;
do {
old = gen;
for (i = 0; i < count; i++)
vdev->config->get(vdev, offset + bytes * i,
buf + i * bytes, bytes);
gen = vdev->config->generation ?
vdev->config->generation(vdev) : 0;
} while (gen != old);
}
static inline void virtio_cread_bytes(struct virtio_device *vdev,
unsigned int offset,
void *buf, size_t len)
{
int i;
for (i = 0; i < len; i++)
vdev->config->get(vdev, offset + i, buf + i, 1);
__virtio_cread_many(vdev, offset, buf, len, 1);
}
static inline void virtio_cwrite8(struct virtio_device *vdev,
@ -352,6 +375,7 @@ static inline u64 virtio_cread64(struct virtio_device *vdev,
{
u64 ret;
vdev->config->get(vdev, offset, &ret, sizeof(ret));
__virtio_cread_many(vdev, offset, &ret, 1, sizeof(ret));
return virtio64_to_cpu(vdev, (__force __virtio64)ret);
}