virtio-ccw: introduce revisions

Provide a new ccw that allows devices and drivers to operate on selected
revision levels.

VIRTIO-42

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>

git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio@86 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652

1 files changed, 83 insertions, 10 deletions

diff --git a/virtio-v1.0-wd01-part1-specification.txt b/virtio-v1.0-wd01-part1-specification.txt
index c2052ec..33ee771 100644
--- a/virtio-v1.0-wd01-part1-specification.txt
+++ b/virtio-v1.0-wd01-part1-specification.txt
@@ -1766,6 +1766,7 @@ 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
 
 The virtio-ccw device acts like a normal channel device, as specified
 in [S390 PoP] and [S390 Common I/O]. In particular:
@@ -1789,7 +1790,79 @@ in [S390 PoP] and [S390 Common I/O]. In particular:
 
 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
+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 device must treat the revision as unset from the time the associated
+subchannel has been enabled until a revision has been successfully set
+by the driver. This implies that revisions are not persistent across
+disabling and enabling of the associated subchannel.
+
+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
@@ -1837,7 +1910,7 @@ struct vq_info_block_legacy {
 queue contains the guest address for queue index, num the number of buffers
 and align the alignment.
 
-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
@@ -1857,14 +1930,14 @@ 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
@@ -1891,7 +1964,7 @@ 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
@@ -1909,7 +1982,7 @@ In both cases, the complete configuration space is transmitted.  This
 allows the guest to compare the new configuration space with the old
 version, and keep a generation count internally whenever it changes.
 
-2.3.3.2.5. Setting Up Indicators
+2.3.3.2.6. Setting Up Indicators
 --------------------------------
 
 In order to set up the indicator bits for host->guest notification,
@@ -1923,7 +1996,7 @@ traditional I/O interrupts is provided, regardless of whether
 traditional or adapter I/O interrupts are used for virtqueue
 notifications.
 
-2.3.3.2.5.1. Setting Up Classic Queue Indicators
+2.3.3.2.6.1. Setting Up Classic Queue Indicators
 ------------------------------------------------
 
 Indicators for notification via classic I/O interrupts are contained
@@ -1938,7 +2011,7 @@ If the driver has already set up two-staged queue indicators via the
 CCW_CMD_SET_IND_ADAPTER command, the device MUST post a unit check
 with command reject to any subsequent CCW_CMD_SET_IND command.
 
-2.3.3.2.5.2. Setting Up Configuration Change Indicators
+2.3.3.2.6.2. Setting Up Configuration Change Indicators
 -------------------------------------------------------
 
 Indicators for configuration change host->guest notification are
@@ -1949,7 +2022,7 @@ configuration change host->guest notification, the driver issues the
 CCW_CMD_SET_CONF_IND command, pointing to a location containing the
 guest address of the indicators in a 64 bit value.
 
-2.3.3.2.5.3. Setting Up Two-Stage Queue Indicators
+2.3.3.2.6.3. Setting Up Two-Stage Queue Indicators
 --------------------------------------------------
 
 Indicators for notification via adapter I/O interrupts consist of
@@ -1983,7 +2056,7 @@ If the driver has already set up classic queue indicators via the
 CCW_CMD_SET_IND command, the device MUST post a unit check with
 command reject to any subsequent CCW_CMD_SET_IND_ADAPTER command.
 
-2.3.3.2.5.4. Legacy Interfaces: A Note on Setting Up Indicators
+2.3.3.2.6.4. Legacy Interfaces: A Note on Setting Up Indicators
 ---------------------------------------------------------------
 
 Legacy devices will only support classic queue indicators; they will