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authorFarhan Ali <alifm@linux.ibm.com>2020-05-05 15:27:41 +0300
committerCornelia Huck <cohuck@redhat.com>2020-06-02 14:14:08 +0300
commit24c986748ba670c903a9d6a11ee96de2b3f5f1b8 (patch)
tree4117927cb0d8a23c596dc72b5e0f22f1213efd46 /Documentation/s390
parent600279b52659c8211c6625fb2c9cd8bf8de15061 (diff)
downloadlinux-24c986748ba670c903a9d6a11ee96de2b3f5f1b8.tar.xz
vfio-ccw: Introduce a new schib region
The schib region can be used by userspace to get the subchannel- information block (SCHIB) for the passthrough subchannel. This can be useful to get information such as channel path information via the SCHIB.PMCW fields. Signed-off-by: Farhan Ali <alifm@linux.ibm.com> Signed-off-by: Eric Farman <farman@linux.ibm.com> Reviewed-by: Cornelia Huck <cohuck@redhat.com> Message-Id: <20200505122745.53208-5-farman@linux.ibm.com> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
Diffstat (limited to 'Documentation/s390')
-rw-r--r--Documentation/s390/vfio-ccw.rst18
1 files changed, 17 insertions, 1 deletions
diff --git a/Documentation/s390/vfio-ccw.rst b/Documentation/s390/vfio-ccw.rst
index 3a946fd45562..32310df525ba 100644
--- a/Documentation/s390/vfio-ccw.rst
+++ b/Documentation/s390/vfio-ccw.rst
@@ -282,6 +282,21 @@ for each access of the region. The following values may occur:
``-EBUSY``
The subchannel was status pending or busy while processing a halt request.
+vfio-ccw schib region
+---------------------
+
+The vfio-ccw schib region is used to return Subchannel-Information
+Block (SCHIB) data to userspace::
+
+ struct ccw_schib_region {
+ #define SCHIB_AREA_SIZE 52
+ __u8 schib_area[SCHIB_AREA_SIZE];
+ } __packed;
+
+This region is exposed via region type VFIO_REGION_SUBTYPE_CCW_SCHIB.
+
+Reading this region triggers a STORE SUBCHANNEL to be issued to the
+associated hardware.
vfio-ccw operation details
--------------------------
@@ -385,7 +400,8 @@ through DASD/ECKD device online in a guest now and use it as a block
device.
The current code allows the guest to start channel programs via
-START SUBCHANNEL, and to issue HALT SUBCHANNEL and CLEAR SUBCHANNEL.
+START SUBCHANNEL, and to issue HALT SUBCHANNEL, CLEAR SUBCHANNEL,
+and STORE SUBCHANNEL.
Currently all channel programs are prefetched, regardless of the
p-bit setting in the ORB. As a result, self modifying channel