diff options
Diffstat (limited to 'virtio-v1.0-wd01-part1-specification.txt')
| -rw-r--r-- | virtio-v1.0-wd01-part1-specification.txt | 27 |
1 files changed, 16 insertions, 11 deletions
diff --git a/virtio-v1.0-wd01-part1-specification.txt b/virtio-v1.0-wd01-part1-specification.txt index bc44492..d92a576 100644 --- a/virtio-v1.0-wd01-part1-specification.txt +++ b/virtio-v1.0-wd01-part1-specification.txt @@ -1598,8 +1598,6 @@ device except where noted. 2.4.2.3. Feature bits -------------------- - VIRTIO_BLK_F_BARRIER (0) Host supports request barriers. - VIRTIO_BLK_F_SIZE_MAX (1) Maximum size of any single segment is in “size_max”. @@ -1634,6 +1632,8 @@ device except where noted. 2.4.2.3.1 Legacy Interface: Feature bits -------------------- + VIRTIO_BLK_F_BARRIER (0) Host supports request barriers. + VIRTIO_BLK_F_SCSI (7) Device supports scsi packet commands. 2.4.2.4. Device Initialization @@ -1668,20 +1668,12 @@ the device (not necessarily in order). Each request is of form: The type of the request is either a read (VIRTIO_BLK_T_IN), a write (VIRTIO_BLK_T_OUT), or a flush (VIRTIO_BLK_T_FLUSH or -VIRTIO_BLK_T_FLUSH_OUT[23]). If the device has VIRTIO_BLK_F_BARRIER -feature the high bit (VIRTIO_BLK_T_BARRIER) indicates that this -request acts as a barrier and that all preceeding requests must be -complete before this one, and all following requests must not be -started until this is complete. Note that a barrier does not flush -caches in the underlying backend device in host, and thus does not -serve as data consistency guarantee. Driver must use FLUSH request to -flush the host cache. +VIRTIO_BLK_T_FLUSH_OUT[23]). #define VIRTIO_BLK_T_IN 0 #define VIRTIO_BLK_T_OUT 1 #define VIRTIO_BLK_T_FLUSH 4 #define VIRTIO_BLK_T_FLUSH_OUT 5 - #define VIRTIO_BLK_T_BARRIER 0x80000000 The ioprio field is a hint about the relative priorities of requests to the device: higher numbers indicate more important @@ -1760,6 +1752,19 @@ data_len, sense_len and residual in a single write-only buffer; and the status field is a separate read-only buffer of size 1 byte, by itself. +2.4.2.5.1. Legacy Interface: Device Operation +------------------------ + #define VIRTIO_BLK_T_BARRIER 0x80000000 + +If the device has VIRTIO_BLK_F_BARRIER +feature the high bit (VIRTIO_BLK_T_BARRIER) indicates that this +request acts as a barrier and that all preceeding requests must be +complete before this one, and all following requests must not be +started until this is complete. Note that a barrier does not flush +caches in the underlying backend device in host, and thus does not +serve as data consistency guarantee. Driver must use FLUSH request to +flush the host cache. + 2.4.3. Console Device ==================== |