summaryrefslogtreecommitdiff
path: root/include/linux/virtio_config.h
diff options
context:
space:
mode:
authorMichael S. Tsirkin <mst@redhat.com>2014-12-14 16:55:44 +0200
committerMichael S. Tsirkin <mst@redhat.com>2014-12-14 18:21:31 +0200
commitd71de9ec6ba806104439d3a669befda84757b5af (patch)
tree9584862eef22a09b0299a3e5e4a975ddc67e1de9 /include/linux/virtio_config.h
parent0dce3771fdd1db03c6f498594a34bba5a6d1f870 (diff)
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>
Diffstat (limited to 'include/linux/virtio_config.h')
-rw-r--r--include/linux/virtio_config.h32
1 files changed, 28 insertions, 4 deletions
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index a61cd37f088c..ca3ed78e5ec7 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -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);
}