error_report() is more appropriate for error situations. Replace fprintf with
error_report() and error_printf() as appropriate. Some improvement in error
reporting also happens as a part of this change. For example:

From:
$ ./qemu-system-x86_64 --accel kvm
Could not access KVM kernel module: No such file or directory

To:
$ ./qemu-system-x86_64 --accel kvm
qemu-system-x86_64: --accel kvm: Could not access KVM kernel module: No such file or directory

CC: qemu-trivial@nongnu.org
CC: zhao1.liu@intel.com
CC: armbru@redhat.com
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Ani Sinha <anisinha@redhat.com>
---
 accel/kvm/kvm-all.c | 40 ++++++++++++++++++----------------------
 1 file changed, 18 insertions(+), 22 deletions(-)

changelog:
v2: fix a bug.
v3: replace one instance of error_report() with error_printf(). added tags.
v4: changes suggested by Markus.
v5: more changes from Markus's comments on v4.
v6: commit message update as per suggestion from Markus. Tag added.

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 75d11a07b2..fcc157f0e6 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -2427,7 +2427,7 @@ static int kvm_init(MachineState *ms)
     QLIST_INIT(&s->kvm_parked_vcpus);
     s->fd = qemu_open_old(s->device ?: "/dev/kvm", O_RDWR);
     if (s->fd == -1) {
-        fprintf(stderr, "Could not access KVM kernel module: %m\n");
+        error_report("Could not access KVM kernel module: %m");
         ret = -errno;
         goto err;
     }
@@ -2437,13 +2437,13 @@ static int kvm_init(MachineState *ms)
         if (ret >= 0) {
             ret = -EINVAL;
         }
-        fprintf(stderr, "kvm version too old\n");
+        error_report("kvm version too old");
         goto err;
     }
 
     if (ret > KVM_API_VERSION) {
         ret = -EINVAL;
-        fprintf(stderr, "kvm version not supported\n");
+        error_report("kvm version not supported");
         goto err;
     }
 
@@ -2488,26 +2488,22 @@ static int kvm_init(MachineState *ms)
     } while (ret == -EINTR);
 
     if (ret < 0) {
-        fprintf(stderr, "ioctl(KVM_CREATE_VM) failed: %d %s\n", -ret,
-                strerror(-ret));
+        error_report("ioctl(KVM_CREATE_VM) failed: %s", strerror(-ret));
 
 #ifdef TARGET_S390X
         if (ret == -EINVAL) {
-            fprintf(stderr,
-                    "Host kernel setup problem detected. Please verify:\n");
-            fprintf(stderr, "- for kernels supporting the switch_amode or"
-                    " user_mode parameters, whether\n");
-            fprintf(stderr,
-                    "  user space is running in primary address space\n");
-            fprintf(stderr,
-                    "- for kernels supporting the vm.allocate_pgste sysctl, "
-                    "whether it is enabled\n");
+            error_printf("Host kernel setup problem detected."
+                         " Please verify:\n");
+            error_printf("- for kernels supporting the"
+                        " switch_amode or user_mode parameters, whether");
+            error_printf(" user space is running in primary address space\n");
+            error_printf("- for kernels supporting the vm.allocate_pgste"
+                         " sysctl, whether it is enabled\n");
         }
 #elif defined(TARGET_PPC)
         if (ret == -EINVAL) {
-            fprintf(stderr,
-                    "PPC KVM module is not loaded. Try modprobe kvm_%s.\n",
-                    (type == 2) ? "pr" : "hv");
+            error_printf("PPC KVM module is not loaded. Try modprobe kvm_%s.\n",
+                         (type == 2) ? "pr" : "hv");
         }
 #endif
         goto err;
@@ -2526,9 +2522,9 @@ static int kvm_init(MachineState *ms)
                         nc->name, nc->num, soft_vcpus_limit);
 
             if (nc->num > hard_vcpus_limit) {
-                fprintf(stderr, "Number of %s cpus requested (%d) exceeds "
-                        "the maximum cpus supported by KVM (%d)\n",
-                        nc->name, nc->num, hard_vcpus_limit);
+                error_report("Number of %s cpus requested (%d) exceeds "
+                             "the maximum cpus supported by KVM (%d)",
+                             nc->name, nc->num, hard_vcpus_limit);
                 exit(1);
             }
         }
@@ -2542,8 +2538,8 @@ static int kvm_init(MachineState *ms)
     }
     if (missing_cap) {
         ret = -EINVAL;
-        fprintf(stderr, "kvm does not support %s\n%s",
-                missing_cap->name, upgrade_note);
+        error_report("kvm does not support %s", missing_cap->name);
+        error_printf("%s", upgrade_note);
         goto err;
     }
 
-- 
2.42.0

Queued, thanks.

Paolo