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