Introduce condition to notify waiters of completed command

Introduce a lock and a condition to notify anyone waiting for the completion
of the execution of a TPM command by the backend (thread). The backend
uses the condition to signal anyone waiting for command completion.
We need to place the condition in two locations: one is invoked by the 
backend thread, the other by the bottom half thread.
We will use the signalling to wait for command completion before VM
suspend.

Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>

hw/tpm/tpm_int.h

@@ -30,6 +30,9 @@ struct TPMState {
     char *backend;
     TPMBackend *be_driver;
     TPMVersion be_tpm_version;
+
+    QemuMutex state_lock;
+    QemuCond cmd_complete;
 };
 
 #define TPM(obj) OBJECT_CHECK(TPMState, (obj), TYPE_TPM_TIS)

hw/tpm/tpm_tis.c

@@ -367,6 +367,8 @@ static void tpm_tis_receive_bh(void *opaque)
     TPMTISEmuState *tis = &s->s.tis;
     uint8_t locty = s->locty_number;
 
+    qemu_mutex_lock(&s->state_lock);
+
     tpm_tis_sts_set(&tis->loc[locty],
                     TPM_TIS_STS_VALID | TPM_TIS_STS_DATA_AVAILABLE);
     tis->loc[locty].state = TPM_TIS_STATE_COMPLETION;
@@ -383,6 +385,10 @@ static void tpm_tis_receive_bh(void *opaque)
     tpm_tis_raise_irq(s, locty,
                       TPM_TIS_INT_DATA_AVAILABLE | TPM_TIS_INT_STS_VALID);
 #endif
+
+    /* notify of completed command */
+    qemu_cond_signal(&s->cmd_complete);
+    qemu_mutex_unlock(&s->state_lock);
 }
 
 /*
@@ -402,6 +408,11 @@ static void tpm_tis_receive_cb(TPMState *s, uint8_t locty,
         }
     }
 
+    qemu_mutex_lock(&s->state_lock);
+    /* notify of completed command */
+    qemu_cond_signal(&s->cmd_complete);
+    qemu_mutex_unlock(&s->state_lock);
+
     qemu_bh_schedule(tis->bh);
 }
 
@@ -1071,6 +1082,9 @@ static void tpm_tis_initfn(Object *obj)
     memory_region_init_io(&s->mmio, OBJECT(s), &tpm_tis_memory_ops,
                           s, "tpm-tis-mmio",
                           TPM_TIS_NUM_LOCALITIES << TPM_TIS_LOCALITY_SHIFT);
+
+    qemu_mutex_init(&s->state_lock);
+    qemu_cond_init(&s->cmd_complete);
 }
 
 static void tpm_tis_class_init(ObjectClass *klass, void *data)