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Commit d71de9ec authored by Michael S. Tsirkin's avatar Michael S. Tsirkin
Browse files

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: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 0dce3771

include/linux/virtio_config.h

+28 −4
Original line number Diff line number Diff line
@@ -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;

}



static inline void virtio_cread_bytes(struct virtio_device *vdev,

/* Read @count fields, @bytes each. */

static inline void __virtio_cread_many(struct virtio_device *vdev,

				       unsigned int offset,

				      void *buf, size_t len)

				       void *buf, size_t count, size_t bytes)

{

	u32 old, gen = vdev->config->generation ?

		vdev->config->generation(vdev) : 0;

	int i;



	for (i = 0; i < len; i++)

		vdev->config->get(vdev, offset + i, buf + i, 1);

	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)

{

	__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);

}