[Qemu-devel] [PATCH 01/10] s390x/css: handle emw correctly for tsch

[Cornelia Huck <cornelia.huck@de.ibm.com>]

We should not try to store the emw portion of the irb if extended
measurements are not applicable. In particular, we should not surprise
the guest by storing a larger irb if it did not enable extended
measurements.

Cc: qemu-stable@nongnu.org
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
---
 hw/s390x/css.c |   24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/hw/s390x/css.c b/hw/s390x/css.c
index 2678e44..a813b23 100644
--- a/hw/s390x/css.c
+++ b/hw/s390x/css.c
@@ -779,9 +779,11 @@ out:
     return ret;
 }
 
-static void copy_irb_to_guest(IRB *dest, const IRB *src)
+static void copy_irb_to_guest(IRB *dest, const IRB *src, PMCW *pmcw)
 {
     int i;
+    uint16_t stctl = src->scsw.ctrl & SCSW_CTRL_MASK_STCTL;
+    uint16_t actl = src->scsw.ctrl & SCSW_CTRL_MASK_ACTL;
 
     copy_scsw_to_guest(&dest->scsw, &src->scsw);
 
@@ -791,8 +793,22 @@ static void copy_irb_to_guest(IRB *dest, const IRB *src)
     for (i = 0; i < ARRAY_SIZE(dest->ecw); i++) {
         dest->ecw[i] = cpu_to_be32(src->ecw[i]);
     }
-    for (i = 0; i < ARRAY_SIZE(dest->emw); i++) {
-        dest->emw[i] = cpu_to_be32(src->emw[i]);
+    /* extended measurements enabled? */
+    if ((src->scsw.flags & SCSW_FLAGS_MASK_ESWF) ||
+        !(pmcw->flags & PMCW_FLAGS_MASK_TF) ||
+        !(pmcw->chars & PMCW_CHARS_MASK_XMWME)) {
+        return;
+    }
+    /* extended measurements pending? */
+    if (!(stctl & SCSW_STCTL_STATUS_PEND)) {
+        return;
+    }
+    if ((stctl & SCSW_STCTL_PRIMARY) ||
+        (stctl == SCSW_STCTL_SECONDARY) ||
+        ((stctl & SCSW_STCTL_INTERMEDIATE) && (actl & SCSW_ACTL_SUSP))) {
+        for (i = 0; i < ARRAY_SIZE(dest->emw); i++) {
+            dest->emw[i] = cpu_to_be32(src->emw[i]);
+        }
     }
 }
 
@@ -838,7 +854,7 @@ int css_do_tsch(SubchDev *sch, IRB *target_irb)
         }
     }
     /* Store the irb to the guest. */
-    copy_irb_to_guest(target_irb, &irb);
+    copy_irb_to_guest(target_irb, &irb, p);
 
     /* Clear conditions on subchannel, if applicable. */
     if (stctl & SCSW_STCTL_STATUS_PEND) {
-- 
1.7.9.5