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Diffstat (limited to 'Documentation/s390/vfio-ccw.rst')
| -rw-r--r-- | Documentation/s390/vfio-ccw.rst | 31 |
1 files changed, 28 insertions, 3 deletions
diff --git a/Documentation/s390/vfio-ccw.rst b/Documentation/s390/vfio-ccw.rst index 1e210c6afa88..fca9c4f5bd9c 100644 --- a/Documentation/s390/vfio-ccw.rst +++ b/Documentation/s390/vfio-ccw.rst @@ -180,6 +180,13 @@ The process of how these work together. add it to an iommu_group and a vfio_group. Then we could pass through the mdev to a guest. + +VFIO-CCW Regions +---------------- + +The vfio-ccw driver exposes MMIO regions to accept requests from and return +results to userspace. + vfio-ccw I/O region ------------------- @@ -205,6 +212,25 @@ irb_area stores the I/O result. ret_code stores a return code for each access of the region. +This region is always available. + +vfio-ccw cmd region +------------------- + +The vfio-ccw cmd region is used to accept asynchronous instructions +from userspace:: + + #define VFIO_CCW_ASYNC_CMD_HSCH (1 << 0) + #define VFIO_CCW_ASYNC_CMD_CSCH (1 << 1) + struct ccw_cmd_region { + __u32 command; + __u32 ret_code; + } __packed; + +This region is exposed via region type VFIO_REGION_SUBTYPE_CCW_ASYNC_CMD. + +Currently, CLEAR SUBCHANNEL and HALT SUBCHANNEL use this region. + vfio-ccw operation details -------------------------- @@ -306,9 +332,8 @@ Together with the corresponding work in QEMU, we can bring the passed through DASD/ECKD device online in a guest now and use it as a block device. -While the current code allows the guest to start channel programs via -START SUBCHANNEL, support for HALT SUBCHANNEL or CLEAR SUBCHANNEL is -not yet implemented. +The current code allows the guest to start channel programs via +START SUBCHANNEL, and to issue HALT SUBCHANNEL and CLEAR SUBCHANNEL. vfio-ccw supports classic (command mode) channel I/O only. Transport mode (HPF) is not supported. |