s390: Fix handling of iscs.

There are two ways to express an interruption subclass:
- As a bitmask, as used in cr6.
- As a number, as used in the I/O interruption word.

Unfortunately, we have treated to I/O interruption word as if it
contained the bitmask as well, which went unnoticed so far as
- (queued-for-next) kvm made the same mistake, and
- Linux guest kernels don't check the isc value in the I/O interruption
  word for subchannel interrupts.

Make sure that we treat the I/O interruption word correctly.

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

1 files changed, 4 insertions, 1 deletions

diff --git a/target-s390x/helper.c b/target-s390x/helper.c
index 9f9088b040..76268317a3 100644
--- a/target-s390x/helper.c
+++ b/target-s390x/helper.c
@@ -628,6 +628,8 @@ static void do_io_interrupt(CPUS390XState *env)
     }
 
     for (isc = 0; isc < ARRAY_SIZE(env->io_index); isc++) {
+        uint64_t isc_bits;
+
         if (env->io_index[isc] < 0) {
             continue;
         }
@@ -637,7 +639,8 @@ static void do_io_interrupt(CPUS390XState *env)
         }
 
         q = &env->io_queue[env->io_index[isc]][isc];
-        if (!(env->cregs[6] & q->word)) {
+        isc_bits = ISC_TO_ISC_BITS(IO_INT_WORD_ISC(q->word));
+        if (!(env->cregs[6] & isc_bits)) {
             disable = 0;
             continue;
         }