diff options
Diffstat (limited to 'virtio-v1.0-wd01-part1-specification.txt')
| -rw-r--r-- | virtio-v1.0-wd01-part1-specification.txt | 84 |
1 files changed, 78 insertions, 6 deletions
diff --git a/virtio-v1.0-wd01-part1-specification.txt b/virtio-v1.0-wd01-part1-specification.txt index e812f8d..a2d3059 100644 --- a/virtio-v1.0-wd01-part1-specification.txt +++ b/virtio-v1.0-wd01-part1-specification.txt @@ -1715,13 +1715,85 @@ virtio: #define CCW_CMD_WRITE_CONF 0x21 #define CCW_CMD_WRITE_STATUS 0x31 #define CCW_CMD_READ_VQ_CONF 0x32 +#define CCW_CMD_SET_VIRTIO_REV 0x83 2.3.3.2. Device Initialization ------------------------------ virtio-ccw uses several channel commands to set up a device. -2.3.3.2.1. Configuring a Virtqueue +2.3.3.2.1. Setting the Virtio Revision +-------------------------------------- + +CCW_CMD_SET_VIRTIO_REV is issued by the driver to set the revision of +the virtio-ccw transport it intends to drive the device with. It uses the +following communication structure: + +struct virtio_rev_info { + __u16 revision; + __u16 length; + __u8 data[]; +}; + +revision contains the desired revision id, length the length of the +data portion and data revision-dependent additional desired options. + +The following values are supported: + +------------------------------------------------------------------ +| revision | length | data | remarks | +|----------|--------|-----------|--------------------------------| +| 0 | 0 | <empty> | legacy interface; transitional | +| | | | devices only | +|----------|--------|-----------|--------------------------------| +| 1 | 0 | <empty> | Virtio 1.0 | +|----------|--------|-----------|--------------------------------| +| 2-n | | | reserved for later revisions | +------------------------------------------------------------------ + +Note that a change in the virtio standard does not neccessarily +correspond to a change in the virtio-ccw revision. + +A device must post a unit check with command reject for any revision +it does not support. For any invalid combination of revision, length +and data, it must post a unit check with command reject as well. A +non-transitional device must reject revision id 0. + +A driver should start with trying to set the highest revision it +supports and continue with lower revisions if it gets a command reject. + +A driver must not issue any other virtio-ccw specific channel commands +other than CCW_CMD_VDEV_RESET prior to setting the revision. + +A device must answer with command reject to any virtio-ccw specific +channel command that is not contained in the revision selected by the +driver. + +After a revision has been successfully selected by the driver, it +must not attempt to select a different revision. A device must answer +to any such attempt with a command reject. + +A virtio reset via CCW_CMD_VDEV_RESET resets the selected revision. +After a reset, the device must react to commands as if no revision had +been selected before. + +2.3.3.2.1.1. Legacy Interfaces: A Note on Setting the Virtio Revision +--------------------------------------------------------------------- + +A legacy device will not support the CCW_CMD_SET_VIRTIO_REV and answer +with a command reject. A non-transitional driver must stop trying to +operate this device in that case. A transitional driver must operate +the device as if it had been able to set revision 0. + +A legacy driver will not issue the CCW_CMD_SET_VIRTIO_REV prior to +issueing other virtio-ccw specific channel commands. A non-transitional +device therefore must answer any such attempts with a command reject. +A transitional device must assume in this case that the driver is a +legacy driver and continue as if the driver selected revision 0. This +implies that the device must reject any command not valid for revision +0, including a subsequent CCW_CMD_SET_VIRTIO_REV. + +2.3.3.2.2. Configuring a Virtqueue ---------------------------------- CCW_CMD_READ_VQ_CONF is issued by the guest to obtain information @@ -1750,7 +1822,7 @@ queue contains the guest address for queue index. The actual number of allocated buffers is transmitted in num and their alignment in align. -100.3.3.2.1. Virtqueue Layout +100.3.3.2.2. Virtqueue Layout ------------------------------ The virtqueue is physically contiguous, with padded added to make the @@ -1770,14 +1842,14 @@ The calculation for total size is as follows: + ALIGN(sizeof(u16)*3 + sizeof(struct vring_used_elem)*num); } -2.3.3.2.2. Communicating Status Information +2.3.3.2.3. Communicating Status Information ------------------------------------------- The guest can change the status of a device via the CCW_CMD_WRITE_STATUS command, which transmits an 8 bit status value. -2.3.3.2.3. Handling Device Features +2.3.3.2.4. Handling Device Features ----------------------------------- Feature bits are arranged in an array of 32 bit values, making @@ -1804,7 +1876,7 @@ For communicating its device features to the host, the guest may use the CCW_CMD_WRITE_FEAT command, denoting a features/index combination. -2.3.3.2.4. Device Configuration +2.3.3.2.5. Device Configuration ------------------------------- The device's configuration space is located in host memory. It is @@ -1820,7 +1892,7 @@ read from. In both cases, the complete configuration space is transmitted. -2.3.3.2.5. Setting Up Indicators +2.3.3.2.6. Setting Up Indicators -------------------------------- To communicate the location of the indicator bits for host->guest |