[Qemu-devel] [PATCH 2/3] s390/css: Fix subchannel detection

[Jens Freimann]

From: Christian Borntraeger <address@hidden>

We have to consider the m bit to find the real channel subsystem when
determining the last subchannel.

If we fail to take this into account, removal of a subchannel in
the middle of a big list of devices will stop device detection after
a reboot.

Signed-off-by: Christian Borntraeger <address@hidden>
Signed-off-by: Jens Freimann <address@hidden>
Reviewed-by: Cornelia Huck <address@hidden>
---
 hw/s390x/css.c        | 11 +++++++----
 target-s390x/cpu.h    |  2 +-
 target-s390x/ioinst.c |  2 +-
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/hw/s390x/css.c b/hw/s390x/css.c
index 3244201..8240e48 100644
--- a/hw/s390x/css.c
+++ b/hw/s390x/css.c
@@ -988,15 +988,18 @@ int css_do_rchp(uint8_t cssid, uint8_t chpid)
     return 0;
 }
 
-bool css_schid_final(uint8_t cssid, uint8_t ssid, uint16_t schid)
+bool css_schid_final(int m, uint8_t cssid, uint8_t ssid, uint16_t schid)
 {
     SubchSet *set;
+    uint8_t real_cssid;
 
-    if (cssid > MAX_CSSID || ssid > MAX_SSID || !channel_subsys->css[cssid] ||
-        !channel_subsys->css[cssid]->sch_set[ssid]) {
+    real_cssid = (!m && (cssid == 0)) ? channel_subsys->default_cssid : cssid;
+    if (real_cssid > MAX_CSSID || ssid > MAX_SSID ||
+        !channel_subsys->css[real_cssid] ||
+        !channel_subsys->css[real_cssid]->sch_set[ssid]) {
         return true;
     }
-    set = channel_subsys->css[cssid]->sch_set[ssid];
+    set = channel_subsys->css[real_cssid]->sch_set[ssid];
     return schid > find_last_bit(set->schids_used,
                                  (MAX_SCHID + 1) / sizeof(unsigned long));
 }
diff --git a/target-s390x/cpu.h b/target-s390x/cpu.h
index 01e59b9..670603a 100644
--- a/target-s390x/cpu.h
+++ b/target-s390x/cpu.h
@@ -405,7 +405,7 @@ SubchDev *css_find_subch(uint8_t m, uint8_t cssid, uint8_t 
ssid,
 bool css_subch_visible(SubchDev *sch);
 void css_conditional_io_interrupt(SubchDev *sch);
 int css_do_stsch(SubchDev *sch, SCHIB *schib);
-bool css_schid_final(uint8_t cssid, uint8_t ssid, uint16_t schid);
+bool css_schid_final(int m, uint8_t cssid, uint8_t ssid, uint16_t schid);
 int css_do_msch(SubchDev *sch, SCHIB *schib);
 int css_do_xsch(SubchDev *sch);
 int css_do_csch(SubchDev *sch);
diff --git a/target-s390x/ioinst.c b/target-s390x/ioinst.c
index e3531f3..28c508d 100644
--- a/target-s390x/ioinst.c
+++ b/target-s390x/ioinst.c
@@ -316,7 +316,7 @@ int ioinst_handle_stsch(CPUS390XState *env, uint64_t reg1, 
uint32_t ipb)
             cc = 3;
         }
     } else {
-        if (css_schid_final(cssid, ssid, schid)) {
+        if (css_schid_final(m, cssid, ssid, schid)) {
             cc = 3; /* No more subchannels in this css/ss */
         } else {
             /* Store an empty schib. */
-- 
1.7.12.4