s390x: fix generation of event information crw

Only one channel report word (crw) may be pending if there is
event-information pending.

This patch introduces a bool-type field 'sei_pending' for the
channel subsystem, which indicates whether there are pending events.
It is set when event information is made pending and the crw
generated, and cleared after the guest has collected all pending
event information. A crw is not generated if this flag had already
been set.

Signed-off-by: Song Shan Gong <gongss@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>

hw/s390x/css.c

@@ -49,6 +49,7 @@ typedef struct IoAdapter {
 
 typedef struct ChannelSubSys {
     QTAILQ_HEAD(, CrwContainer) pending_crws;
+    bool sei_pending;
     bool do_crw_mchk;
     bool crws_lost;
     uint8_t max_cssid;
@@ -1359,7 +1360,15 @@ void css_generate_chp_crws(uint8_t cssid, uint8_t chpid)
 
 void css_generate_css_crws(uint8_t cssid)
 {
-    css_queue_crw(CRW_RSC_CSS, 0, 0, cssid);
+    if (!channel_subsys->sei_pending) {
+        css_queue_crw(CRW_RSC_CSS, 0, 0, cssid);
+    }
+    channel_subsys->sei_pending = true;
+}
+
+void css_clear_sei_pending(void)
+{
+    channel_subsys->sei_pending = false;
 }
 
 int css_enable_mcsse(void)
@@ -1509,6 +1518,7 @@ static void css_init(void)
 {
     channel_subsys = g_malloc0(sizeof(*channel_subsys));
     QTAILQ_INIT(&channel_subsys->pending_crws);
+    channel_subsys->sei_pending = false;
     channel_subsys->do_crw_mchk = true;
     channel_subsys->crws_lost = false;
     channel_subsys->chnmon_active = false;
@@ -1561,6 +1571,7 @@ void css_reset(void)
         QTAILQ_REMOVE(&channel_subsys->pending_crws, crw_cont, sibling);
         g_free(crw_cont);
     }
+    channel_subsys->sei_pending = false;
     channel_subsys->do_crw_mchk = true;
     channel_subsys->crws_lost = false;
 

hw/s390x/css.h

@@ -103,6 +103,7 @@ void css_generate_sch_crws(uint8_t cssid, uint8_t ssid, uint16_t schid,
                            int hotplugged, int add);
 void css_generate_chp_crws(uint8_t cssid, uint8_t chpid);
 void css_generate_css_crws(uint8_t cssid);
+void css_clear_sei_pending(void);
 void css_adapter_interrupt(uint8_t isc);
 
 #define CSS_IO_ADAPTER_VIRTIO 1

target-s390x/ioinst.c

@@ -614,6 +614,7 @@ static void ioinst_handle_chsc_sei(ChscReq *req, ChscResp *res)
             (*res_flags) |= 0x80;
         } else {
             (*res_flags) &= ~0x80;
+            css_clear_sei_pending();
         }
     } else {
         res->code = cpu_to_be16(0x0005);