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vfio-ccw: Update documentation for csch/hsch

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We now support CLEAR SUBCHANNEL and HALT SUBCHANNEL
via ccw_cmd_region.

Fixes: d5afd5d135 ("vfio-ccw: add handling for async channel instructions")
Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
Message-Id: <7d977612c3f3152ffb950d77ae11b4b25c1e20c4.1562854091.git.alifm@linux.ibm.com>
[CH: properly mark region as literal block]
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
This commit is contained in:
Farhan Ali 2019-07-11 10:28:55 -04:00 committed by Cornelia Huck
parent f4c9939433
commit 127e621740
1 changed files with 28 additions and 3 deletions
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31
Documentation/s390/vfio-ccw.rst
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@ -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.