Currently the only difference between smp_parse and pc_smp_parse
is the support of dies parameter and the related error reporting.
With some arch compat variables like "bool dies_supported", we can
make smp_parse generic enough for all arches and the PC specific
one can be removed.

Making smp_parse() generic enough can reduce code duplication and
ease the code maintenance, and also allows extending the topology
with more arch specific members (e.g., clusters) in the future.

Suggested-by: Andrew Jones <drjones@redhat.com>
Suggested-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
---
 hw/core/machine.c   | 91 +++++++++++++++++++++++++++++++++++----------
 hw/i386/pc.c        | 84 +----------------------------------------
 include/hw/boards.h |  9 +++++
 3 files changed, 81 insertions(+), 103 deletions(-)

diff --git a/hw/core/machine.c b/hw/core/machine.c
index a21fcd7700..f5dadcbd78 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -746,20 +746,69 @@ void machine_set_cpu_numa_node(MachineState *machine,
     }
 }
 
+/*
+ * Report information of a machine's supported CPU topology hierarchy.
+ * Topology members will be ordered from the largest to the smallest
+ * in the string.
+ */
+static char *cpu_hierarchy_to_string(MachineState *ms)
+{
+    MachineClass *mc = MACHINE_GET_CLASS(ms);
+    GString *s = g_string_new(NULL);
+
+    g_string_append_printf(s, "sockets (%u)", ms->smp.sockets);
+
+    if (mc->smp_props.dies_supported) {
+        g_string_append_printf(s, " * dies (%u)", ms->smp.dies);
+    }
+
+    g_string_append_printf(s, " * cores (%u)", ms->smp.cores);
+    g_string_append_printf(s, " * threads (%u)", ms->smp.threads);
+
+    return g_string_free(s, false);
+}
+
+/*
+ * smp_parse - Generic function used to parse the given SMP configuration
+ *
+ * Any missing parameter in "cpus/maxcpus/sockets/cores/threads" will be
+ * automatically computed based on the provided ones.
+ *
+ * In the calculation of omitted sockets/cores/threads: we prefer sockets
+ * over cores over threads before 6.2, while preferring cores over sockets
+ * over threads since 6.2.
+ *
+ * In the calculation of cpus/maxcpus: When both maxcpus and cpus are omitted,
+ * maxcpus will be computed from the given parameters and cpus will be set
+ * equal to maxcpus. When only one of maxcpus and cpus is given then the
+ * omitted one will be set to its given counterpart's value. Both maxcpus and
+ * cpus may be specified, but maxcpus must be equal to or greater than cpus.
+ *
+ * For compatibility, apart from the parameters that will be computed, newly
+ * introduced topology members which are likely to be target specific should
+ * be directly set as 1 if they are omitted (e.g. dies for PC since 4.1).
+ */
 static void smp_parse(MachineState *ms, SMPConfiguration *config, Error **errp)
 {
     MachineClass *mc = MACHINE_GET_CLASS(ms);
     unsigned cpus    = config->has_cpus ? config->cpus : 0;
     unsigned sockets = config->has_sockets ? config->sockets : 0;
+    unsigned dies    = config->has_dies ? config->dies : 0;
     unsigned cores   = config->has_cores ? config->cores : 0;
     unsigned threads = config->has_threads ? config->threads : 0;
     unsigned maxcpus = config->has_maxcpus ? config->maxcpus : 0;
 
-    if (config->has_dies && config->dies > 1) {
+    /*
+     * If not supported by the machine, a topology parameter must be
+     * omitted or specified equal to 1.
+     */
+    if (!mc->smp_props.dies_supported && dies > 1) {
         error_setg(errp, "dies not supported by this machine's CPU topology");
         return;
     }
 
+    dies = dies > 0 ? dies : 1;
+
     /* compute missing values based on the provided ones */
     if (cpus == 0 && maxcpus == 0) {
         sockets = sockets > 0 ? sockets : 1;
@@ -773,55 +822,57 @@ static void smp_parse(MachineState *ms, SMPConfiguration *config, Error **errp)
             if (sockets == 0) {
                 cores = cores > 0 ? cores : 1;
                 threads = threads > 0 ? threads : 1;
-                sockets = maxcpus / (cores * threads);
+                sockets = maxcpus / (dies * cores * threads);
             } else if (cores == 0) {
                 threads = threads > 0 ? threads : 1;
-                cores = maxcpus / (sockets * threads);
+                cores = maxcpus / (sockets * dies * threads);
             }
         } else {
             /* prefer cores over sockets since 6.2 */
             if (cores == 0) {
                 sockets = sockets > 0 ? sockets : 1;
                 threads = threads > 0 ? threads : 1;
-                cores = maxcpus / (sockets * threads);
+                cores = maxcpus / (sockets * dies * threads);
             } else if (sockets == 0) {
                 threads = threads > 0 ? threads : 1;
-                sockets = maxcpus / (cores * threads);
+                sockets = maxcpus / (dies * cores * threads);
             }
         }
 
         /* try to calculate omitted threads at last */
         if (threads == 0) {
-            threads = maxcpus / (sockets * cores);
+            threads = maxcpus / (sockets * dies * cores);
         }
     }
 
-    maxcpus = maxcpus > 0 ? maxcpus : sockets * cores * threads;
+    maxcpus = maxcpus > 0 ? maxcpus : sockets * dies * cores * threads;
     cpus = cpus > 0 ? cpus : maxcpus;
 
-    if (sockets * cores * threads != maxcpus) {
+    ms->smp.cpus = cpus;
+    ms->smp.sockets = sockets;
+    ms->smp.dies = dies;
+    ms->smp.cores = cores;
+    ms->smp.threads = threads;
+    ms->smp.max_cpus = maxcpus;
+
+    /* sanity-check of the computed topology */
+    if (sockets * dies * cores * threads != maxcpus) {
+        g_autofree char *topo_msg = cpu_hierarchy_to_string(ms);
         error_setg(errp, "Invalid CPU topology: "
                    "product of the hierarchy must match maxcpus: "
-                   "sockets (%u) * cores (%u) * threads (%u) "
-                   "!= maxcpus (%u)",
-                   sockets, cores, threads, maxcpus);
+                   "%s != maxcpus (%u)",
+                   topo_msg, maxcpus);
         return;
     }
 
     if (maxcpus < cpus) {
+        g_autofree char *topo_msg = cpu_hierarchy_to_string(ms);
         error_setg(errp, "Invalid CPU topology: "
                    "maxcpus must be equal to or greater than smp: "
-                   "sockets (%u) * cores (%u) * threads (%u) "
-                   "== maxcpus (%u) < smp_cpus (%u)",
-                   sockets, cores, threads, maxcpus, cpus);
+                   "%s == maxcpus (%u) < smp_cpus (%u)",
+                   topo_msg, maxcpus, cpus);
         return;
     }
-
-    ms->smp.cpus = cpus;
-    ms->smp.sockets = sockets;
-    ms->smp.cores = cores;
-    ms->smp.threads = threads;
-    ms->smp.max_cpus = maxcpus;
 }
 
 static void machine_get_smp(Object *obj, Visitor *v, const char *name,
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 447114e57a..468fe8e0fb 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -710,88 +710,6 @@ void pc_acpi_smi_interrupt(void *opaque, int irq, int level)
     }
 }
 
-/*
- * This function is very similar to smp_parse()
- * in hw/core/machine.c but includes CPU die support.
- */
-static void pc_smp_parse(MachineState *ms, SMPConfiguration *config, Error **errp)
-{
-    MachineClass *mc = MACHINE_GET_CLASS(ms);
-    unsigned cpus    = config->has_cpus ? config->cpus : 0;
-    unsigned sockets = config->has_sockets ? config->sockets : 0;
-    unsigned dies    = config->has_dies ? config->dies : 0;
-    unsigned cores   = config->has_cores ? config->cores : 0;
-    unsigned threads = config->has_threads ? config->threads : 0;
-    unsigned maxcpus = config->has_maxcpus ? config->maxcpus : 0;
-
-    /* directly default dies to 1 if it's omitted */
-    dies = dies > 0 ? dies : 1;
-
-    /* compute missing values based on the provided ones */
-    if (cpus == 0 && maxcpus == 0) {
-        sockets = sockets > 0 ? sockets : 1;
-        cores = cores > 0 ? cores : 1;
-        threads = threads > 0 ? threads : 1;
-    } else {
-        maxcpus = maxcpus > 0 ? maxcpus : cpus;
-
-        if (mc->smp_prefer_sockets) {
-            /* prefer sockets over cores before 6.2 */
-            if (sockets == 0) {
-                cores = cores > 0 ? cores : 1;
-                threads = threads > 0 ? threads : 1;
-                sockets = maxcpus / (dies * cores * threads);
-            } else if (cores == 0) {
-                threads = threads > 0 ? threads : 1;
-                cores = maxcpus / (sockets * dies * threads);
-            }
-        } else {
-            /* prefer cores over sockets since 6.2 */
-            if (cores == 0) {
-                sockets = sockets > 0 ? sockets : 1;
-                threads = threads > 0 ? threads : 1;
-                cores = maxcpus / (sockets * dies * threads);
-            } else if (sockets == 0) {
-                threads = threads > 0 ? threads : 1;
-                sockets = maxcpus / (dies * cores * threads);
-            }
-        }
-
-        /* try to calculate omitted threads at last */
-        if (threads == 0) {
-            threads = maxcpus / (sockets * dies * cores);
-        }
-    }
-
-    maxcpus = maxcpus > 0 ? maxcpus : sockets * dies * cores * threads;
-    cpus = cpus > 0 ? cpus : maxcpus;
-
-    if (sockets * dies * cores * threads != maxcpus) {
-        error_setg(errp, "Invalid CPU topology: "
-                   "product of the hierarchy must match maxcpus: "
-                   "sockets (%u) * dies (%u) * cores (%u) * threads (%u) "
-                   "!= maxcpus (%u)",
-                   sockets, dies, cores, threads, maxcpus);
-        return;
-    }
-
-    if (maxcpus < cpus) {
-        error_setg(errp, "Invalid CPU topology: "
-                   "maxcpus must be equal to or greater than smp: "
-                   "sockets (%u) * dies (%u) * cores (%u) * threads (%u) "
-                   "== maxcpus (%u) < smp_cpus (%u)",
-                   sockets, dies, cores, threads, maxcpus, cpus);
-        return;
-    }
-
-    ms->smp.cpus = cpus;
-    ms->smp.sockets = sockets;
-    ms->smp.dies = dies;
-    ms->smp.cores = cores;
-    ms->smp.threads = threads;
-    ms->smp.max_cpus = maxcpus;
-}
-
 static
 void pc_machine_done(Notifier *notifier, void *data)
 {
@@ -1742,7 +1660,6 @@ static void pc_machine_class_init(ObjectClass *oc, void *data)
     mc->auto_enable_numa_with_memdev = true;
     mc->has_hotpluggable_cpus = true;
     mc->default_boot_order = "cad";
-    mc->smp_parse = pc_smp_parse;
     mc->block_default_type = IF_IDE;
     mc->max_cpus = 255;
     mc->reset = pc_machine_reset;
@@ -1753,6 +1670,7 @@ static void pc_machine_class_init(ObjectClass *oc, void *data)
     hc->unplug = pc_machine_device_unplug_cb;
     mc->default_cpu_type = TARGET_DEFAULT_CPU_TYPE;
     mc->nvdimm_supported = true;
+    mc->smp_props.dies_supported = true;
     mc->default_ram_id = "pc.ram";
 
     object_class_property_add(oc, PC_MACHINE_MAX_RAM_BELOW_4G, "size",
diff --git a/include/hw/boards.h b/include/hw/boards.h
index 2a1bba86c0..72a23e4e0f 100644
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -108,6 +108,14 @@ typedef struct {
     CPUArchId cpus[];
 } CPUArchIdList;
 
+/**
+ * SMPCompatProps:
+ * @dies_supported - whether dies are supported by the machine
+ */
+typedef struct {
+    bool dies_supported;
+} SMPCompatProps;
+
 /**
  * MachineClass:
  * @deprecation_reason: If set, the machine is marked as deprecated. The
@@ -248,6 +256,7 @@ struct MachineClass {
     bool numa_mem_supported;
     bool auto_enable_numa;
     bool smp_prefer_sockets;
+    SMPCompatProps smp_props;
     const char *default_ram_id;
 
     HotplugHandler *(*get_hotplug_handler)(MachineState *machine,
-- 
2.19.1

On Tue, Sep 28, 2021 at 11:57:52AM +0800, Yanan Wang wrote:
> Currently the only difference between smp_parse and pc_smp_parse
> is the support of dies parameter and the related error reporting.
> With some arch compat variables like "bool dies_supported", we can
> make smp_parse generic enough for all arches and the PC specific
> one can be removed.
> 
> Making smp_parse() generic enough can reduce code duplication and
> ease the code maintenance, and also allows extending the topology
> with more arch specific members (e.g., clusters) in the future.
> 
> Suggested-by: Andrew Jones <drjones@redhat.com>
> Suggested-by: Daniel P. Berrange <berrange@redhat.com>
> Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
> ---
>  hw/core/machine.c   | 91 +++++++++++++++++++++++++++++++++++----------
>  hw/i386/pc.c        | 84 +----------------------------------------
>  include/hw/boards.h |  9 +++++
>  3 files changed, 81 insertions(+), 103 deletions(-)

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

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 9/28/21 05:57, Yanan Wang wrote:
> Currently the only difference between smp_parse and pc_smp_parse
> is the support of dies parameter and the related error reporting.
> With some arch compat variables like "bool dies_supported", we can
> make smp_parse generic enough for all arches and the PC specific
> one can be removed.
> 
> Making smp_parse() generic enough can reduce code duplication and
> ease the code maintenance, and also allows extending the topology
> with more arch specific members (e.g., clusters) in the future.
> 
> Suggested-by: Andrew Jones <drjones@redhat.com>
> Suggested-by: Daniel P. Berrange <berrange@redhat.com>
> Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
> ---
>  hw/core/machine.c   | 91 +++++++++++++++++++++++++++++++++++----------
>  hw/i386/pc.c        | 84 +----------------------------------------
>  include/hw/boards.h |  9 +++++
>  3 files changed, 81 insertions(+), 103 deletions(-)

> +/*
> + * smp_parse - Generic function used to parse the given SMP configuration
> + *
> + * Any missing parameter in "cpus/maxcpus/sockets/cores/threads" will be
> + * automatically computed based on the provided ones.
> + *
> + * In the calculation of omitted sockets/cores/threads: we prefer sockets
> + * over cores over threads before 6.2, while preferring cores over sockets
> + * over threads since 6.2.
> + *
> + * In the calculation of cpus/maxcpus: When both maxcpus and cpus are omitted,
> + * maxcpus will be computed from the given parameters and cpus will be set
> + * equal to maxcpus. When only one of maxcpus and cpus is given then the
> + * omitted one will be set to its given counterpart's value. Both maxcpus and
> + * cpus may be specified, but maxcpus must be equal to or greater than cpus.
> + *
> + * For compatibility, apart from the parameters that will be computed, newly
> + * introduced topology members which are likely to be target specific should
> + * be directly set as 1 if they are omitted (e.g. dies for PC since 4.1).
> + */
>  static void smp_parse(MachineState *ms, SMPConfiguration *config, Error **errp)

Can we have it return a boolean instead?

On Tue, Sep 28, 2021 at 12:57:21PM +0200, Philippe Mathieu-Daudé wrote:
> On 9/28/21 05:57, Yanan Wang wrote:
> > Currently the only difference between smp_parse and pc_smp_parse
> > is the support of dies parameter and the related error reporting.
> > With some arch compat variables like "bool dies_supported", we can
> > make smp_parse generic enough for all arches and the PC specific
> > one can be removed.
> > 
> > Making smp_parse() generic enough can reduce code duplication and
> > ease the code maintenance, and also allows extending the topology
> > with more arch specific members (e.g., clusters) in the future.
> > 
> > Suggested-by: Andrew Jones <drjones@redhat.com>
> > Suggested-by: Daniel P. Berrange <berrange@redhat.com>
> > Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
> > ---
> >  hw/core/machine.c   | 91 +++++++++++++++++++++++++++++++++++----------
> >  hw/i386/pc.c        | 84 +----------------------------------------
> >  include/hw/boards.h |  9 +++++
> >  3 files changed, 81 insertions(+), 103 deletions(-)
> 
> > +/*
> > + * smp_parse - Generic function used to parse the given SMP configuration
> > + *
> > + * Any missing parameter in "cpus/maxcpus/sockets/cores/threads" will be
> > + * automatically computed based on the provided ones.
> > + *
> > + * In the calculation of omitted sockets/cores/threads: we prefer sockets
> > + * over cores over threads before 6.2, while preferring cores over sockets
> > + * over threads since 6.2.
> > + *
> > + * In the calculation of cpus/maxcpus: When both maxcpus and cpus are omitted,
> > + * maxcpus will be computed from the given parameters and cpus will be set
> > + * equal to maxcpus. When only one of maxcpus and cpus is given then the
> > + * omitted one will be set to its given counterpart's value. Both maxcpus and
> > + * cpus may be specified, but maxcpus must be equal to or greater than cpus.
> > + *
> > + * For compatibility, apart from the parameters that will be computed, newly
> > + * introduced topology members which are likely to be target specific should
> > + * be directly set as 1 if they are omitted (e.g. dies for PC since 4.1).
> > + */
> >  static void smp_parse(MachineState *ms, SMPConfiguration *config, Error **errp)
> 
> Can we have it return a boolean instead?

That's unrelated to this change, so ought to be a separate commit if
done.

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

On 9/28/21 12:58, Daniel P. Berrangé wrote:
> On Tue, Sep 28, 2021 at 12:57:21PM +0200, Philippe Mathieu-Daudé wrote:
>> On 9/28/21 05:57, Yanan Wang wrote:
>>> Currently the only difference between smp_parse and pc_smp_parse
>>> is the support of dies parameter and the related error reporting.
>>> With some arch compat variables like "bool dies_supported", we can
>>> make smp_parse generic enough for all arches and the PC specific
>>> one can be removed.
>>>
>>> Making smp_parse() generic enough can reduce code duplication and
>>> ease the code maintenance, and also allows extending the topology
>>> with more arch specific members (e.g., clusters) in the future.
>>>
>>> Suggested-by: Andrew Jones <drjones@redhat.com>
>>> Suggested-by: Daniel P. Berrange <berrange@redhat.com>
>>> Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
>>> ---
>>>  hw/core/machine.c   | 91 +++++++++++++++++++++++++++++++++++----------
>>>  hw/i386/pc.c        | 84 +----------------------------------------
>>>  include/hw/boards.h |  9 +++++
>>>  3 files changed, 81 insertions(+), 103 deletions(-)
>>
>>> +/*
>>> + * smp_parse - Generic function used to parse the given SMP configuration
>>> + *
>>> + * Any missing parameter in "cpus/maxcpus/sockets/cores/threads" will be
>>> + * automatically computed based on the provided ones.
>>> + *
>>> + * In the calculation of omitted sockets/cores/threads: we prefer sockets
>>> + * over cores over threads before 6.2, while preferring cores over sockets
>>> + * over threads since 6.2.
>>> + *
>>> + * In the calculation of cpus/maxcpus: When both maxcpus and cpus are omitted,
>>> + * maxcpus will be computed from the given parameters and cpus will be set
>>> + * equal to maxcpus. When only one of maxcpus and cpus is given then the
>>> + * omitted one will be set to its given counterpart's value. Both maxcpus and
>>> + * cpus may be specified, but maxcpus must be equal to or greater than cpus.
>>> + *
>>> + * For compatibility, apart from the parameters that will be computed, newly
>>> + * introduced topology members which are likely to be target specific should
>>> + * be directly set as 1 if they are omitted (e.g. dies for PC since 4.1).
>>> + */
>>>  static void smp_parse(MachineState *ms, SMPConfiguration *config, Error **errp)
>>
>> Can we have it return a boolean instead?
> 
> That's unrelated to this change, so ought to be a separate commit if
> done.

Sure, fine by me.

On 2021/9/28 18:58, Daniel P. Berrangé wrote:
> On Tue, Sep 28, 2021 at 12:57:21PM +0200, Philippe Mathieu-Daudé wrote:
>> On 9/28/21 05:57, Yanan Wang wrote:
>>> Currently the only difference between smp_parse and pc_smp_parse
>>> is the support of dies parameter and the related error reporting.
>>> With some arch compat variables like "bool dies_supported", we can
>>> make smp_parse generic enough for all arches and the PC specific
>>> one can be removed.
>>>
>>> Making smp_parse() generic enough can reduce code duplication and
>>> ease the code maintenance, and also allows extending the topology
>>> with more arch specific members (e.g., clusters) in the future.
>>>
>>> Suggested-by: Andrew Jones <drjones@redhat.com>
>>> Suggested-by: Daniel P. Berrange <berrange@redhat.com>
>>> Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
>>> ---
>>>   hw/core/machine.c   | 91 +++++++++++++++++++++++++++++++++++----------
>>>   hw/i386/pc.c        | 84 +----------------------------------------
>>>   include/hw/boards.h |  9 +++++
>>>   3 files changed, 81 insertions(+), 103 deletions(-)
>>> +/*
>>> + * smp_parse - Generic function used to parse the given SMP configuration
>>> + *
>>> + * Any missing parameter in "cpus/maxcpus/sockets/cores/threads" will be
>>> + * automatically computed based on the provided ones.
>>> + *
>>> + * In the calculation of omitted sockets/cores/threads: we prefer sockets
>>> + * over cores over threads before 6.2, while preferring cores over sockets
>>> + * over threads since 6.2.
>>> + *
>>> + * In the calculation of cpus/maxcpus: When both maxcpus and cpus are omitted,
>>> + * maxcpus will be computed from the given parameters and cpus will be set
>>> + * equal to maxcpus. When only one of maxcpus and cpus is given then the
>>> + * omitted one will be set to its given counterpart's value. Both maxcpus and
>>> + * cpus may be specified, but maxcpus must be equal to or greater than cpus.
>>> + *
>>> + * For compatibility, apart from the parameters that will be computed, newly
>>> + * introduced topology members which are likely to be target specific should
>>> + * be directly set as 1 if they are omitted (e.g. dies for PC since 4.1).
>>> + */
>>>   static void smp_parse(MachineState *ms, SMPConfiguration *config, Error **errp)
>> Can we have it return a boolean instead?
> That's unrelated to this change, so ought to be a separate commit if
> done.
>
I agree. I vaguely remember that there was a discussion about this before
with Paolo. But anyway, I think the suggested change can be in a separate
commit if necessary. :)

Thanks,
Yanan

Philippe Mathieu-Daudé <philmd@redhat.com> writes:

> On 9/28/21 05:57, Yanan Wang wrote:
>> Currently the only difference between smp_parse and pc_smp_parse
>> is the support of dies parameter and the related error reporting.
>> With some arch compat variables like "bool dies_supported", we can
>> make smp_parse generic enough for all arches and the PC specific
>> one can be removed.
>> 
>> Making smp_parse() generic enough can reduce code duplication and
>> ease the code maintenance, and also allows extending the topology
>> with more arch specific members (e.g., clusters) in the future.
>> 
>> Suggested-by: Andrew Jones <drjones@redhat.com>
>> Suggested-by: Daniel P. Berrange <berrange@redhat.com>
>> Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
>> ---
>>  hw/core/machine.c   | 91 +++++++++++++++++++++++++++++++++++----------
>>  hw/i386/pc.c        | 84 +----------------------------------------
>>  include/hw/boards.h |  9 +++++
>>  3 files changed, 81 insertions(+), 103 deletions(-)
>
>> +/*
>> + * smp_parse - Generic function used to parse the given SMP configuration
>> + *
>> + * Any missing parameter in "cpus/maxcpus/sockets/cores/threads" will be
>> + * automatically computed based on the provided ones.
>> + *
>> + * In the calculation of omitted sockets/cores/threads: we prefer sockets
>> + * over cores over threads before 6.2, while preferring cores over sockets
>> + * over threads since 6.2.
>> + *
>> + * In the calculation of cpus/maxcpus: When both maxcpus and cpus are omitted,
>> + * maxcpus will be computed from the given parameters and cpus will be set
>> + * equal to maxcpus. When only one of maxcpus and cpus is given then the
>> + * omitted one will be set to its given counterpart's value. Both maxcpus and
>> + * cpus may be specified, but maxcpus must be equal to or greater than cpus.
>> + *
>> + * For compatibility, apart from the parameters that will be computed, newly
>> + * introduced topology members which are likely to be target specific should
>> + * be directly set as 1 if they are omitted (e.g. dies for PC since 4.1).
>> + */
>>  static void smp_parse(MachineState *ms, SMPConfiguration *config, Error **errp)
>
> Can we have it return a boolean instead?

Yes, please.  From error.h's big comment:

 * = Rules =
[...]
 * - Whenever practical, also return a value that indicates success /
 *   failure.  This can make the error checking more concise, and can
 *   avoid useless error object creation and destruction.  Note that
 *   we still have many functions returning void.  We recommend
 *   • bool-valued functions return true on success / false on failure,
 *   • pointer-valued functions return non-null / null pointer, and
 *   • integer-valued functions return non-negative / negative.

On 2021/9/28 20:25, Markus Armbruster wrote:
> Philippe Mathieu-Daudé <philmd@redhat.com> writes:
>
>> On 9/28/21 05:57, Yanan Wang wrote:
>>> Currently the only difference between smp_parse and pc_smp_parse
>>> is the support of dies parameter and the related error reporting.
>>> With some arch compat variables like "bool dies_supported", we can
>>> make smp_parse generic enough for all arches and the PC specific
>>> one can be removed.
>>>
>>> Making smp_parse() generic enough can reduce code duplication and
>>> ease the code maintenance, and also allows extending the topology
>>> with more arch specific members (e.g., clusters) in the future.
>>>
>>> Suggested-by: Andrew Jones <drjones@redhat.com>
>>> Suggested-by: Daniel P. Berrange <berrange@redhat.com>
>>> Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
>>> ---
>>>   hw/core/machine.c   | 91 +++++++++++++++++++++++++++++++++++----------
>>>   hw/i386/pc.c        | 84 +----------------------------------------
>>>   include/hw/boards.h |  9 +++++
>>>   3 files changed, 81 insertions(+), 103 deletions(-)
>>> +/*
>>> + * smp_parse - Generic function used to parse the given SMP configuration
>>> + *
>>> + * Any missing parameter in "cpus/maxcpus/sockets/cores/threads" will be
>>> + * automatically computed based on the provided ones.
>>> + *
>>> + * In the calculation of omitted sockets/cores/threads: we prefer sockets
>>> + * over cores over threads before 6.2, while preferring cores over sockets
>>> + * over threads since 6.2.
>>> + *
>>> + * In the calculation of cpus/maxcpus: When both maxcpus and cpus are omitted,
>>> + * maxcpus will be computed from the given parameters and cpus will be set
>>> + * equal to maxcpus. When only one of maxcpus and cpus is given then the
>>> + * omitted one will be set to its given counterpart's value. Both maxcpus and
>>> + * cpus may be specified, but maxcpus must be equal to or greater than cpus.
>>> + *
>>> + * For compatibility, apart from the parameters that will be computed, newly
>>> + * introduced topology members which are likely to be target specific should
>>> + * be directly set as 1 if they are omitted (e.g. dies for PC since 4.1).
>>> + */
>>>   static void smp_parse(MachineState *ms, SMPConfiguration *config, Error **errp)
>> Can we have it return a boolean instead?
> Yes, please.  From error.h's big comment:
>
>   * = Rules =
> [...]
>   * - Whenever practical, also return a value that indicates success /
>   *   failure.  This can make the error checking more concise, and can
>   *   avoid useless error object creation and destruction.  Note that
>   *   we still have many functions returning void.  We recommend
>   *   • bool-valued functions return true on success / false on failure,
>   *   • pointer-valued functions return non-null / null pointer, and
>   *   • integer-valued functions return non-negative / negative.
Ok. I will add an extra patch to this series to do the change and respin.
In practice the boolean return value will also make a smp parsing unit
test more concise. (I'm planning to introduce one test).

Thanks,
Yanan