Re: [PATCH v5 1/2] kvm: replace fprintf with error_report()/printf() in kvm_init()

[Markus Armbruster <armbru@redhat.com>]

Ani Sinha <anisinha@redhat.com> writes:

> error_report() is more appropriate for error situations. Replace fprintf with
> error_report() and error_printf() as appropriate. Cosmetic. No functional
> change.

Uh, I missed this last time around: the change is more than just
cosmetics!  The error messages change, e.g. from

    $ qemu-system-x86_64 -nodefaults -S -display none --accel kvm
    qemu-system-x86_64: --accel kvm: Could not access KVM kernel module: Permission denied
    qemu-system-x86_64: --accel kvm: failed to initialize kvm: Permission denied

to

    $ qemu-system-x86_64 -nodefaults -S -display none --accel kvm
    Could not access KVM kernel module: Permission denied
    qemu-system-x86_64: --accel kvm: failed to initialize kvm: Permission denied

Note: the second message is from kvm_init()'s caller.  Reporting the
same error twice is wrong, but not this patch's problem.

Moreover, the patch tweaks an error message at [*].

Suggest something like

  Replace fprintf() with error_report() and error_printf() where
  appropriate.  Error messages improve, e.g. from

      Could not access KVM kernel module: Permission denied

  to

      qemu-system-x86_64: --accel kvm: Could not access KVM kernel module: Permission denied

> CC: qemu-trivial@nongnu.org
> CC: zhao1.liu@intel.com
> CC: armbru@redhat.com
> Reviewed-by: Zhao Liu <zhao1.liu@intel.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.
>
> 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));

[*] This is where you change an error message.

>  
>  #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;
>      }

With the commit message corrected:
Reviewed-by: Markus Armbruster <armbru@redhat.com>