KVM: s390: introduce ais mode modify function

Provide an interface for userspace to modify AIS
(adapter-interruption-suppression) mode state, and add documentation
for the interface. Allowed target modes are ALL-Interruptions mode
and SINGLE-Interruption mode.

We introduce the 'simm' and 'nimm' fields in kvm_s390_float_interrupt
to store interruption modes for each ISC. Each bit in 'simm' and
'nimm' targets to one ISC, and collaboratively indicate three modes:
ALL-Interruptions, SINGLE-Interruption and NO-Interruptions. This
interface can initiate most transitions between the states; transition
from SINGLE-Interruption to NO-Interruptions via adapter interrupt
injection will be introduced in a following patch. The meaningful
combinations are as follows:

    interruption mode | simm bit | nimm bit
    ------------------|----------|----------
             ALL      |    0     |     0
           SINGLE     |    1     |     0
             NO       |    1     |     1

Besides, add tracepoint to track AIS mode transitions.

Co-Authored-By: Yi Min Zhao <zyimin@linux.vnet.ibm.com>
Signed-off-by: Yi Min Zhao <zyimin@linux.vnet.ibm.com>
Signed-off-by: Fei Li <sherrylf@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

1 files changed, 31 insertions, 0 deletions

diff --git a/arch/s390/kvm/trace-s390.h b/arch/s390/kvm/trace-s390.h
index 396485bca191..b32994d1546a 100644
--- a/arch/s390/kvm/trace-s390.h
+++ b/arch/s390/kvm/trace-s390.h
@@ -280,6 +280,37 @@ TRACE_EVENT(kvm_s390_enable_disable_ibs,
 		      __entry->state ? "enabling" : "disabling", __entry->id)
 	);
 
+/*
+ * Trace point for modifying ais mode for a given isc.
+ */
+TRACE_EVENT(kvm_s390_modify_ais_mode,
+	    TP_PROTO(__u8 isc, __u16 from, __u16 to),
+	    TP_ARGS(isc, from, to),
+
+	    TP_STRUCT__entry(
+		    __field(__u8, isc)
+		    __field(__u16, from)
+		    __field(__u16, to)
+		    ),
+
+	    TP_fast_assign(
+		    __entry->isc = isc;
+		    __entry->from = from;
+		    __entry->to = to;
+		    ),
+
+	    TP_printk("for isc %x, modifying interruption mode from %s to %s",
+		      __entry->isc,
+		      (__entry->from == KVM_S390_AIS_MODE_ALL) ?
+		      "ALL-Interruptions Mode" :
+		      (__entry->from == KVM_S390_AIS_MODE_SINGLE) ?
+		      "Single-Interruption Mode" : "No-Interruptions Mode",
+		      (__entry->to == KVM_S390_AIS_MODE_ALL) ?
+		      "ALL-Interruptions Mode" :
+		      (__entry->to == KVM_S390_AIS_MODE_SINGLE) ?
+		      "Single-Interruption Mode" : "No-Interruptions Mode")
+	);
+
 
 #endif /* _TRACE_KVMS390_H */