scsi: Fix SCSI bus reset

When the controller raises the SCSI reset line, we have to perform the
requested reset on all disks attached to the controller's bus. Moreover,
reset is edge triggered, so avoid repeating it if the line was already
high.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/lsi53c895a.c

@@ -1590,8 +1590,19 @@ static void lsi_reg_writeb(LSIState *s, int offset, uint8_t val)
             BADF("Immediate Arbritration not implemented\n");
         }
         if (val & LSI_SCNTL1_RST) {
-            s->sstat0 |= LSI_SSTAT0_RST;
-            lsi_script_scsi_interrupt(s, LSI_SIST0_RST, 0);
+            if (!(s->sstat0 & LSI_SSTAT0_RST)) {
+                DeviceState *dev;
+                int id;
+
+                for (id = 0; id < s->bus.ndev; id++) {
+                    if (s->bus.devs[id]) {
+                        dev = &s->bus.devs[id]->qdev;
+                        dev->info->reset(dev);
+                    }
+                }
+                s->sstat0 |= LSI_SSTAT0_RST;
+                lsi_script_scsi_interrupt(s, LSI_SIST0_RST, 0);
+            }
         } else {
             s->sstat0 &= ~LSI_SSTAT0_RST;
         }