hw/tpm: Make TRACE_TPM_UTIL_SHOW_BUFFER check local to tpm_util.c

The trace_event_get_state_backends() call is useful to avoid
making extensive calls (usually preparing arguments passed to
the tracing framework. In this case, the extensive work is
done in tpm_util_show_buffer(), and the arguments used to
call it don't involve extra processing. Simplify by moving
the TRACE_TPM_UTIL_SHOW_BUFFER check to tpm_util_show_buffer.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Message-id: 20200612085444.8362-9-philmd@redhat.com
Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>

hw/tpm/tpm_tis_common.c

@@ -78,9 +78,7 @@ static void tpm_tis_sts_set(TPMLocality *l, uint32_t flags)
  */
 static void tpm_tis_tpm_send(TPMState *s, uint8_t locty)
 {
-    if (trace_event_get_state_backends(TRACE_TPM_UTIL_SHOW_BUFFER)) {
-        tpm_util_show_buffer(s->buffer, s->be_buffer_size, "To TPM");
-    }
+    tpm_util_show_buffer(s->buffer, s->be_buffer_size, "To TPM");
 
     /*
      * rw_offset serves as length indicator for length of data;
@@ -246,9 +244,7 @@ void tpm_tis_request_completed(TPMState *s, int ret)
     s->loc[locty].state = TPM_TIS_STATE_COMPLETION;
     s->rw_offset = 0;
 
-    if (trace_event_get_state_backends(TRACE_TPM_UTIL_SHOW_BUFFER)) {
-        tpm_util_show_buffer(s->buffer, s->be_buffer_size, "From TPM");
-    }
+    tpm_util_show_buffer(s->buffer, s->be_buffer_size, "From TPM");
 
     if (TPM_TIS_IS_VALID_LOCTY(s->next_locty)) {
         tpm_tis_abort(s);

hw/tpm/tpm_util.c

@@ -357,6 +357,9 @@ void tpm_util_show_buffer(const unsigned char *buffer,
     size_t len, i;
     char *line_buffer, *p;
 
+    if (!trace_event_get_state_backends(TRACE_TPM_UTIL_SHOW_BUFFER)) {
+        return;
+    }
     len = MIN(tpm_cmd_get_size(buffer), buffer_size);
 
     /*