In the SMP configuration, we should either provide a topology
parameter with a reasonable value (greater than zero) or just
omit it and QEMU will compute the missing value.

The users shouldn't provide a configuration with any parameter
of it specified as zero (e.g. -smp 8,sockets=0) which could
possibly cause unexpected results in the -smp parsing. So we
deprecate this kind of configurations since 6.2 by adding the
explicit sanity check.

Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
---
 docs/about/deprecated.rst | 15 +++++++++++++++
 hw/core/machine.c         | 14 ++++++++++++++
 qapi/machine.json         |  2 +-
 qemu-options.hx           | 12 +++++++-----
 4 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
index 3c2be84d80..97415dbecd 100644
--- a/docs/about/deprecated.rst
+++ b/docs/about/deprecated.rst
@@ -160,6 +160,21 @@ Use ``-display sdl`` instead.
 
 Use ``-display curses`` instead.
 
+``-smp`` ("parameter=0" SMP configurations) (since 6.2)
+'''''''''''''''''''''''''''''''''''''''''''''''''''''''
+
+Specified CPU topology parameters must be greater than zero.
+
+In the SMP configuration, users should either provide a CPU topology
+parameter with a reasonable value (greater than zero) or just omit it
+and QEMU will compute the missing value.
+
+However, historically it was implicitly allowed for users to provide
+a parameter with zero value, which is meaningless and could also possibly
+cause unexpected results in the -smp parsing. So support for this kind of
+configurations (e.g. -smp 8,sockets=0) is deprecated since 6.2 and will
+be removed in the near future, users have to ensure that all the topology
+members described with -smp are greater than zero.
 
 Plugin argument passing through ``arg=<string>`` (since 6.1)
 ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
diff --git a/hw/core/machine.c b/hw/core/machine.c
index 067f42b528..711e83db54 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -835,6 +835,20 @@ static void machine_set_smp(Object *obj, Visitor *v, const char *name,
         return;
     }
 
+    /*
+     * Specified CPU topology parameters must be greater than zero,
+     * explicit configuration like "cpus=0" is not allowed.
+     */
+    if ((config->has_cpus && config->cpus == 0) ||
+        (config->has_sockets && config->sockets == 0) ||
+        (config->has_dies && config->dies == 0) ||
+        (config->has_cores && config->cores == 0) ||
+        (config->has_threads && config->threads == 0) ||
+        (config->has_maxcpus && config->maxcpus == 0)) {
+        warn_report("Invalid CPU topology deprecated: "
+                    "CPU topology parameters must be greater than zero");
+    }
+
     mc->smp_parse(ms, config, errp);
     if (*errp) {
         goto out_free;
diff --git a/qapi/machine.json b/qapi/machine.json
index 32d47f4e35..227e75d8af 100644
--- a/qapi/machine.json
+++ b/qapi/machine.json
@@ -1331,7 +1331,7 @@
 #
 # @dies: number of dies per socket in the CPU topology
 #
-# @cores: number of cores per thread in the CPU topology
+# @cores: number of cores per die in the CPU topology
 #
 # @threads: number of threads per core in the CPU topology
 #
diff --git a/qemu-options.hx b/qemu-options.hx
index 8f603cc7e6..91d859aa29 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -227,11 +227,13 @@ SRST
     of computing the CPU maximum count.
 
     Either the initial CPU count, or at least one of the topology parameters
-    must be specified. Values for any omitted parameters will be computed
-    from those which are given. Historically preference was given to the
-    coarsest topology parameters when computing missing values (ie sockets
-    preferred over cores, which were preferred over threads), however, this
-    behaviour is considered liable to change.
+    must be specified. The specified parameters must be greater than zero,
+    explicit configuration like "cpus=0" is not allowed. Values for any
+    omitted parameters will be computed from those which are given.
+    Historically preference was given to the coarsest topology parameters
+    when computing missing values (ie sockets preferred over cores, which
+    were preferred over threads), however, this behaviour is considered
+    liable to change.
 ERST
 
 DEF("numa", HAS_ARG, QEMU_OPTION_numa,
-- 
2.19.1

On Tue, Sep 28, 2021 at 11:57:42AM +0800, Yanan Wang wrote:
> In the SMP configuration, we should either provide a topology
> parameter with a reasonable value (greater than zero) or just
> omit it and QEMU will compute the missing value.
> 
> The users shouldn't provide a configuration with any parameter
> of it specified as zero (e.g. -smp 8,sockets=0) which could
> possibly cause unexpected results in the -smp parsing. So we
> deprecate this kind of configurations since 6.2 by adding the
> explicit sanity check.
> 
> Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
> ---
>  docs/about/deprecated.rst | 15 +++++++++++++++
>  hw/core/machine.c         | 14 ++++++++++++++
>  qapi/machine.json         |  2 +-
>  qemu-options.hx           | 12 +++++++-----
>  4 files changed, 37 insertions(+), 6 deletions(-)
> 
> diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
> index 3c2be84d80..97415dbecd 100644
> --- a/docs/about/deprecated.rst
> +++ b/docs/about/deprecated.rst
> @@ -160,6 +160,21 @@ Use ``-display sdl`` instead.
>  
>  Use ``-display curses`` instead.
>  
> +``-smp`` ("parameter=0" SMP configurations) (since 6.2)
> +'''''''''''''''''''''''''''''''''''''''''''''''''''''''
> +
> +Specified CPU topology parameters must be greater than zero.
> +
> +In the SMP configuration, users should either provide a CPU topology
> +parameter with a reasonable value (greater than zero) or just omit it
> +and QEMU will compute the missing value.
> +
> +However, historically it was implicitly allowed for users to provide
> +a parameter with zero value, which is meaningless and could also possibly
> +cause unexpected results in the -smp parsing. So support for this kind of
> +configurations (e.g. -smp 8,sockets=0) is deprecated since 6.2 and will
> +be removed in the near future, users have to ensure that all the topology
> +members described with -smp are greater than zero.
>  
>  Plugin argument passing through ``arg=<string>`` (since 6.1)
>  ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index 067f42b528..711e83db54 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -835,6 +835,20 @@ static void machine_set_smp(Object *obj, Visitor *v, const char *name,
>          return;
>      }
>  
> +    /*
> +     * Specified CPU topology parameters must be greater than zero,
> +     * explicit configuration like "cpus=0" is not allowed.
> +     */
> +    if ((config->has_cpus && config->cpus == 0) ||
> +        (config->has_sockets && config->sockets == 0) ||
> +        (config->has_dies && config->dies == 0) ||
> +        (config->has_cores && config->cores == 0) ||
> +        (config->has_threads && config->threads == 0) ||
> +        (config->has_maxcpus && config->maxcpus == 0)) {
> +        warn_report("Invalid CPU topology deprecated: "
> +                    "CPU topology parameters must be greater than zero");
> +    }
> +
>      mc->smp_parse(ms, config, errp);
>      if (*errp) {
>          goto out_free;
> diff --git a/qapi/machine.json b/qapi/machine.json
> index 32d47f4e35..227e75d8af 100644
> --- a/qapi/machine.json
> +++ b/qapi/machine.json
> @@ -1331,7 +1331,7 @@
>  #
>  # @dies: number of dies per socket in the CPU topology
>  #
> -# @cores: number of cores per thread in the CPU topology
> +# @cores: number of cores per die in the CPU topology
>  #
>  # @threads: number of threads per core in the CPU topology
>  #

This change is unrelated to the rest of this commit.

It just looks like a simple bug fix and should just be
spun out into its own patch.

> diff --git a/qemu-options.hx b/qemu-options.hx
> index 8f603cc7e6..91d859aa29 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -227,11 +227,13 @@ SRST
>      of computing the CPU maximum count.
>  
>      Either the initial CPU count, or at least one of the topology parameters
> -    must be specified. Values for any omitted parameters will be computed
> -    from those which are given. Historically preference was given to the
> -    coarsest topology parameters when computing missing values (ie sockets
> -    preferred over cores, which were preferred over threads), however, this
> -    behaviour is considered liable to change.
> +    must be specified. The specified parameters must be greater than zero,
> +    explicit configuration like "cpus=0" is not allowed. Values for any
> +    omitted parameters will be computed from those which are given.
> +    Historically preference was given to the coarsest topology parameters
> +    when computing missing values (ie sockets preferred over cores, which
> +    were preferred over threads), however, this behaviour is considered
> +    liable to change.
>  ERST
>  
>  DEF("numa", HAS_ARG, QEMU_OPTION_numa,

If you split the docs fix out into its own patch then you can add

  Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

to both this patch and the new patch.

Regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|

On 2021/9/28 17:58, Daniel P. Berrangé wrote:
> On Tue, Sep 28, 2021 at 11:57:42AM +0800, Yanan Wang wrote:
>> In the SMP configuration, we should either provide a topology
>> parameter with a reasonable value (greater than zero) or just
>> omit it and QEMU will compute the missing value.
>>
>> The users shouldn't provide a configuration with any parameter
>> of it specified as zero (e.g. -smp 8,sockets=0) which could
>> possibly cause unexpected results in the -smp parsing. So we
>> deprecate this kind of configurations since 6.2 by adding the
>> explicit sanity check.
>>
>> Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
>> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
>> ---
>>   docs/about/deprecated.rst | 15 +++++++++++++++
>>   hw/core/machine.c         | 14 ++++++++++++++
>>   qapi/machine.json         |  2 +-
>>   qemu-options.hx           | 12 +++++++-----
>>   4 files changed, 37 insertions(+), 6 deletions(-)
>>
>> diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
>> index 3c2be84d80..97415dbecd 100644
>> --- a/docs/about/deprecated.rst
>> +++ b/docs/about/deprecated.rst
>> @@ -160,6 +160,21 @@ Use ``-display sdl`` instead.
>>   
>>   Use ``-display curses`` instead.
>>   
>> +``-smp`` ("parameter=0" SMP configurations) (since 6.2)
>> +'''''''''''''''''''''''''''''''''''''''''''''''''''''''
>> +
>> +Specified CPU topology parameters must be greater than zero.
>> +
>> +In the SMP configuration, users should either provide a CPU topology
>> +parameter with a reasonable value (greater than zero) or just omit it
>> +and QEMU will compute the missing value.
>> +
>> +However, historically it was implicitly allowed for users to provide
>> +a parameter with zero value, which is meaningless and could also possibly
>> +cause unexpected results in the -smp parsing. So support for this kind of
>> +configurations (e.g. -smp 8,sockets=0) is deprecated since 6.2 and will
>> +be removed in the near future, users have to ensure that all the topology
>> +members described with -smp are greater than zero.
>>   
>>   Plugin argument passing through ``arg=<string>`` (since 6.1)
>>   ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
>> diff --git a/hw/core/machine.c b/hw/core/machine.c
>> index 067f42b528..711e83db54 100644
>> --- a/hw/core/machine.c
>> +++ b/hw/core/machine.c
>> @@ -835,6 +835,20 @@ static void machine_set_smp(Object *obj, Visitor *v, const char *name,
>>           return;
>>       }
>>   
>> +    /*
>> +     * Specified CPU topology parameters must be greater than zero,
>> +     * explicit configuration like "cpus=0" is not allowed.
>> +     */
>> +    if ((config->has_cpus && config->cpus == 0) ||
>> +        (config->has_sockets && config->sockets == 0) ||
>> +        (config->has_dies && config->dies == 0) ||
>> +        (config->has_cores && config->cores == 0) ||
>> +        (config->has_threads && config->threads == 0) ||
>> +        (config->has_maxcpus && config->maxcpus == 0)) {
>> +        warn_report("Invalid CPU topology deprecated: "
>> +                    "CPU topology parameters must be greater than zero");
>> +    }
>> +
>>       mc->smp_parse(ms, config, errp);
>>       if (*errp) {
>>           goto out_free;
>> diff --git a/qapi/machine.json b/qapi/machine.json
>> index 32d47f4e35..227e75d8af 100644
>> --- a/qapi/machine.json
>> +++ b/qapi/machine.json
>> @@ -1331,7 +1331,7 @@
>>   #
>>   # @dies: number of dies per socket in the CPU topology
>>   #
>> -# @cores: number of cores per thread in the CPU topology
>> +# @cores: number of cores per die in the CPU topology
>>   #
>>   # @threads: number of threads per core in the CPU topology
>>   #
> This change is unrelated to the rest of this commit.
>
> It just looks like a simple bug fix and should just be
> spun out into its own patch.
>
>> diff --git a/qemu-options.hx b/qemu-options.hx
>> index 8f603cc7e6..91d859aa29 100644
>> --- a/qemu-options.hx
>> +++ b/qemu-options.hx
>> @@ -227,11 +227,13 @@ SRST
>>       of computing the CPU maximum count.
>>   
>>       Either the initial CPU count, or at least one of the topology parameters
>> -    must be specified. Values for any omitted parameters will be computed
>> -    from those which are given. Historically preference was given to the
>> -    coarsest topology parameters when computing missing values (ie sockets
>> -    preferred over cores, which were preferred over threads), however, this
>> -    behaviour is considered liable to change.
>> +    must be specified. The specified parameters must be greater than zero,
>> +    explicit configuration like "cpus=0" is not allowed. Values for any
>> +    omitted parameters will be computed from those which are given.
>> +    Historically preference was given to the coarsest topology parameters
>> +    when computing missing values (ie sockets preferred over cores, which
>> +    were preferred over threads), however, this behaviour is considered
>> +    liable to change.
>>   ERST
>>   
>>   DEF("numa", HAS_ARG, QEMU_OPTION_numa,
> If you split the docs fix out into its own patch then you can add
Ok, I will split it out. Thanks for the review of this series.

Thanks,
Yanan
>
>    Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
>
> to both this patch and the new patch.
>
> Regards,
> Daniel