diff --git a/linux-user/alpha/cpu_loop.c b/linux-user/alpha/cpu_loop.c
index b87fcaea87..c1a98c8cbf 100644
--- a/linux-user/alpha/cpu_loop.c
+++ b/linux-user/alpha/cpu_loop.c
@@ -196,7 +196,7 @@ void cpu_loop(CPUAlphaState *env)
             arch_interrupt = false;
             break;
         default:
-            printf ("Unhandled trap: 0x%x\n", trapnr);
+            fprintf(stderr, "Unhandled trap: 0x%x\n", trapnr);
             cpu_dump_state(cs, stderr, fprintf, 0);
             exit(EXIT_FAILURE);
         }
diff --git a/linux-user/cris/cpu_loop.c b/linux-user/cris/cpu_loop.c
index 1c5eca9f83..37bdcfa8cc 100644
--- a/linux-user/cris/cpu_loop.c
+++ b/linux-user/cris/cpu_loop.c
@@ -81,7 +81,7 @@ void cpu_loop(CPUCRISState *env)
             cpu_exec_step_atomic(cs);
             break;
         default:
-            printf ("Unhandled trap: 0x%x\n", trapnr);
+            fprintf(stderr, "Unhandled trap: 0x%x\n", trapnr);
             cpu_dump_state(cs, stderr, fprintf, 0);
             exit(EXIT_FAILURE);
         }
diff --git a/linux-user/cris/signal.c b/linux-user/cris/signal.c
index 0b405247cf..1e02194377 100644
--- a/linux-user/cris/signal.c
+++ b/linux-user/cris/signal.c
@@ -146,7 +146,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
                     target_siginfo_t *info,
                      target_sigset_t *set, CPUCRISState *env)
 {
-    fprintf(stderr, "CRIS setup_rt_frame: not implemented\n");
+    qemu_log_mask(LOG_UNIMP, "setup_rt_frame: not implemented\n");
 }
 
 long do_sigreturn(CPUCRISState *env)
@@ -183,6 +183,6 @@ badframe:
 long do_rt_sigreturn(CPUCRISState *env)
 {
     trace_user_do_rt_sigreturn(env, 0);
-    fprintf(stderr, "CRIS do_rt_sigreturn: not implemented\n");
+    qemu_log_mask(LOG_UNIMP, "do_rt_sigreturn: not implemented\n");
     return -TARGET_ENOSYS;
 }
diff --git a/linux-user/microblaze/cpu_loop.c b/linux-user/microblaze/cpu_loop.c
index 5af12d5b21..2af93eb39a 100644
--- a/linux-user/microblaze/cpu_loop.c
+++ b/linux-user/microblaze/cpu_loop.c
@@ -105,8 +105,8 @@ void cpu_loop(CPUMBState *env)
                     queue_signal(env, info.si_signo, QEMU_SI_FAULT, &info);
                     break;
                 default:
-                    printf("Unhandled hw-exception: 0x%" PRIx64 "\n",
-                           env->sregs[SR_ESR] & ESR_EC_MASK);
+                    fprintf(stderr, "Unhandled hw-exception: 0x%" PRIx64 "\n",
+                            env->sregs[SR_ESR] & ESR_EC_MASK);
                     cpu_dump_state(cs, stderr, fprintf, 0);
                     exit(EXIT_FAILURE);
                     break;
@@ -130,7 +130,7 @@ void cpu_loop(CPUMBState *env)
             cpu_exec_step_atomic(cs);
             break;
         default:
-            printf ("Unhandled trap: 0x%x\n", trapnr);
+            fprintf(stderr, "Unhandled trap: 0x%x\n", trapnr);
             cpu_dump_state(cs, stderr, fprintf, 0);
             exit(EXIT_FAILURE);
         }
diff --git a/linux-user/microblaze/signal.c b/linux-user/microblaze/signal.c
index 712ee522b2..80950c2181 100644
--- a/linux-user/microblaze/signal.c
+++ b/linux-user/microblaze/signal.c
@@ -200,7 +200,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
                     target_siginfo_t *info,
                     target_sigset_t *set, CPUMBState *env)
 {
-    fprintf(stderr, "Microblaze setup_rt_frame: not implemented\n");
+    qemu_log_mask(LOG_UNIMP, "setup_rt_frame: not implemented\n");
 }
 
 long do_sigreturn(CPUMBState *env)
@@ -240,6 +240,6 @@ badframe:
 long do_rt_sigreturn(CPUMBState *env)
 {
     trace_user_do_rt_sigreturn(env, 0);
-    fprintf(stderr, "Microblaze do_rt_sigreturn: not implemented\n");
+    qemu_log_mask(LOG_UNIMP, "do_rt_sigreturn: not implemented\n");
     return -TARGET_ENOSYS;
 }
diff --git a/linux-user/nios2/signal.c b/linux-user/nios2/signal.c
index 4985dc2212..7d535065ed 100644
--- a/linux-user/nios2/signal.c
+++ b/linux-user/nios2/signal.c
@@ -203,7 +203,7 @@ give_sigsegv:
 long do_sigreturn(CPUNios2State *env)
 {
     trace_user_do_sigreturn(env, 0);
-    fprintf(stderr, "do_sigreturn: not implemented\n");
+    qemu_log_mask(LOG_UNIMP, "do_sigreturn: not implemented\n");
     return -TARGET_ENOSYS;
 }
 
diff --git a/linux-user/sh4/cpu_loop.c b/linux-user/sh4/cpu_loop.c
index 418833ea25..fdd348170b 100644
--- a/linux-user/sh4/cpu_loop.c
+++ b/linux-user/sh4/cpu_loop.c
@@ -84,7 +84,7 @@ void cpu_loop(CPUSH4State *env)
             arch_interrupt = false;
             break;
         default:
-            printf ("Unhandled trap: 0x%x\n", trapnr);
+            fprintf(stderr, "Unhandled trap: 0x%x\n", trapnr);
             cpu_dump_state(cs, stderr, fprintf, 0);
             exit(EXIT_FAILURE);
         }
diff --git a/linux-user/sparc/cpu_loop.c b/linux-user/sparc/cpu_loop.c
index 7c4796ca23..91f714afc6 100644
--- a/linux-user/sparc/cpu_loop.c
+++ b/linux-user/sparc/cpu_loop.c
@@ -285,7 +285,7 @@ void cpu_loop (CPUSPARCState *env)
             cpu_exec_step_atomic(cs);
             break;
         default:
-            printf ("Unhandled trap: 0x%x\n", trapnr);
+            fprintf(stderr, "Unhandled trap: 0x%x\n", trapnr);
             cpu_dump_state(cs, stderr, fprintf, 0);
             exit(EXIT_FAILURE);
         }
diff --git a/linux-user/sparc/signal.c b/linux-user/sparc/signal.c
index 55e9d6f9b2..b4c60aa446 100644
--- a/linux-user/sparc/signal.c
+++ b/linux-user/sparc/signal.c
@@ -278,7 +278,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
                     target_siginfo_t *info,
                     target_sigset_t *set, CPUSPARCState *env)
 {
-    fprintf(stderr, "setup_rt_frame: not implemented\n");
+    qemu_log_mask(LOG_UNIMP, "setup_rt_frame: not implemented\n");
 }
 
 long do_sigreturn(CPUSPARCState *env)
@@ -357,7 +357,7 @@ segv_and_exit:
 long do_rt_sigreturn(CPUSPARCState *env)
 {
     trace_user_do_rt_sigreturn(env, 0);
-    fprintf(stderr, "do_rt_sigreturn: not implemented\n");
+    qemu_log_mask(LOG_UNIMP, "do_rt_sigreturn: not implemented\n");
     return -TARGET_ENOSYS;
 }
 
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 5822e03e28..e4b1b7d7da 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -12757,7 +12757,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
 
     default:
     unimplemented:
-        gemu_log("qemu: Unsupported syscall: %d\n", num);
+        qemu_log_mask(LOG_UNIMP, "Unsupported syscall: %d\n", num);
 #if defined(TARGET_NR_setxattr) || defined(TARGET_NR_get_thread_area) || defined(TARGET_NR_getdomainname) || defined(TARGET_NR_set_robust_list)
     unimplemented_nowarn:
 #endif