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

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

[Ani Sinha]

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

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));
 
 #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

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

[Markus Armbruster]

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>

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

[Ani Sinha]

> On 28 Aug 2024, at 4:53 PM, Markus Armbruster <armbru@redhat.com> wrote:
> 
> 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

You got this backwards. This is what I have:

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

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


> 
> 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

Yes this seems correct.

> 
>> 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>

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

[Markus Armbruster]

Ani Sinha <anisinha@redhat.com> writes:

>> On 28 Aug 2024, at 4:53 PM, Markus Armbruster <armbru@redhat.com> wrote:
>> 
>> 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
>
> You got this backwards. This is what I have:

I do!  Sorry %-}

[...]

[PATCH v5 2/2] kvm: refactor core virtual machine creation into its own function

[Ani Sinha]

Refactoring the core logic around KVM_CREATE_VM into its own separate function
so that it can be called from other functions in future patches. There is
no functional change in this patch.

CC: pbonzini@redhat.com
CC: zhao1.liu@intel.com
CC: cfontana@suse.de
CC: armbru@redhat.com
CC: qemu-trivial@nongnu.org
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Claudio Fontana <cfontana@suse.de>
Signed-off-by: Ani Sinha <anisinha@redhat.com>
---
 accel/kvm/kvm-all.c | 86 ++++++++++++++++++++++++++++-----------------
 1 file changed, 53 insertions(+), 33 deletions(-)

v2: s/fprintf/warn_report as suggested by zhao
v3: s/warn_report/error_report. function names adjusted to conform to
other names. fprintf -> error_report() moved to its own patch.
v4: added tags and rebased.
v5: rebased.

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index fcc157f0e6..cf3d820b94 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -2385,6 +2385,57 @@ uint32_t kvm_dirty_ring_size(void)
     return kvm_state->kvm_dirty_ring_size;
 }
 
+static int kvm_create_vm(MachineState *ms, KVMState *s, int type)
+{
+    int ret;
+
+    do {
+        ret = kvm_ioctl(s, KVM_CREATE_VM, type);
+    } while (ret == -EINTR);
+
+    if (ret < 0) {
+        error_report("ioctl(KVM_CREATE_VM) failed: %s", strerror(-ret));
+
+#ifdef TARGET_S390X
+        if (ret == -EINVAL) {
+            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) {
+            error_printf("PPC KVM module is not loaded. Try modprobe kvm_%s.\n",
+                         (type == 2) ? "pr" : "hv");
+        }
+#endif
+    }
+
+    return ret;
+}
+
+static int kvm_machine_type(MachineState *ms)
+{
+    MachineClass *mc = MACHINE_GET_CLASS(ms);
+    int type;
+
+    if (object_property_find(OBJECT(current_machine), "kvm-type")) {
+        g_autofree char *kvm_type;
+        kvm_type = object_property_get_str(OBJECT(current_machine),
+                                           "kvm-type",
+                                           &error_abort);
+        type = mc->kvm_type(ms, kvm_type);
+    } else if (mc->kvm_type) {
+        type = mc->kvm_type(ms, NULL);
+    } else {
+        type = kvm_arch_get_default_type(ms);
+    }
+    return type;
+}
+
 static int kvm_init(MachineState *ms)
 {
     MachineClass *mc = MACHINE_GET_CLASS(ms);
@@ -2467,45 +2518,14 @@ static int kvm_init(MachineState *ms)
     }
     s->as = g_new0(struct KVMAs, s->nr_as);
 
-    if (object_property_find(OBJECT(current_machine), "kvm-type")) {
-        g_autofree char *kvm_type = object_property_get_str(OBJECT(current_machine),
-                                                            "kvm-type",
-                                                            &error_abort);
-        type = mc->kvm_type(ms, kvm_type);
-    } else if (mc->kvm_type) {
-        type = mc->kvm_type(ms, NULL);
-    } else {
-        type = kvm_arch_get_default_type(ms);
-    }
-
+    type = kvm_machine_type(ms);
     if (type < 0) {
         ret = -EINVAL;
         goto err;
     }
 
-    do {
-        ret = kvm_ioctl(s, KVM_CREATE_VM, type);
-    } while (ret == -EINTR);
-
+    ret = kvm_create_vm(ms, s, type);
     if (ret < 0) {
-        error_report("ioctl(KVM_CREATE_VM) failed: %s", strerror(-ret));
-
-#ifdef TARGET_S390X
-        if (ret == -EINVAL) {
-            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) {
-            error_printf("PPC KVM module is not loaded. Try modprobe kvm_%s.\n",
-                         (type == 2) ? "pr" : "hv");
-        }
-#endif
         goto err;
     }
 
-- 
2.42.0