Re: [PATCH V1 01/32] savevm: add vmstate handler iterators

[Steven Sistare]

On 9/11/2020 12:24 PM, Dr. David Alan Gilbert wrote:
> Apologies for taking a while to get around to this, 
> 
> * Steve Sistare (steven.sistare@oracle.com) wrote:
>> Provide the SAVEVM_FOREACH and SAVEVM_FORALL macros to loop over all save
>> VM state handlers.  The former will filter handlers based on the operation
>> in the later patch "savevm: VM handlers mode mask".  The latter loops over
>> all handlers.
>>
>> No functional change.
>>
>> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
>> ---
>>  migration/savevm.c | 57 
>> ++++++++++++++++++++++++++++++++++++------------------
>>  1 file changed, 38 insertions(+), 19 deletions(-)
>>
>> diff --git a/migration/savevm.c b/migration/savevm.c
>> index 45c9dd9..a07fcad 100644
>> --- a/migration/savevm.c
>> +++ b/migration/savevm.c
>> @@ -266,6 +266,25 @@ static SaveState savevm_state = {
>>      .global_section_id = 0,
>>  };
>>  
>> +/*
>> + * The FOREACH macros will filter handlers based on the current operation 
>> when
>> + * additional conditions are added in a subsequent patch.
>> + */
>> +
>> +#define SAVEVM_FOREACH(se, entry)                                    \
>> +    QTAILQ_FOREACH(se, &savevm_state.handlers, entry)                \
>> +
>> +#define SAVEVM_FOREACH_SAFE(se, entry, new_se)                       \
>> +    QTAILQ_FOREACH_SAFE(se, &savevm_state.handlers, entry, new_se)   \
>> +
>> +/* The FORALL macros unconditionally loop over all handlers. */
>> +
>> +#define SAVEVM_FORALL(se, entry)                                     \
>> +    QTAILQ_FOREACH(se, &savevm_state.handlers, entry)
>> +
>> +#define SAVEVM_FORALL_SAFE(se, entry, new_se)                        \
>> +    QTAILQ_FOREACH_SAFE(se, &savevm_state.handlers, entry, new_se)
>> +
> 
> OK, can I ask you to merge this with the next patch but to spin it the
> other way, so that we have:
> 
>   SAVEVM_FOR(se, entry, mask)
> 
> and the places you use SAVEVM_FORALL_SAFE would become
> 
>   SAVEVM_FOR(se, entry, VMS_MODE_ALL)
> 
> I'm thinking at some point in the future we could merge a bunch of the
> other flag checks in there.

Sure.  Is this what you have in mind?

#define SAVEVM_FOR(se, entry, mask)                    \
    QTAILQ_FOREACH(se, &savevm_state.handlers, entry)  \
        if (savevm_state.mode & mask)

#define SAVEVM_FOR_SAFE(se, entry, new_se, mask)                    \
    QTAILQ_FOREACH_SAFE(se, &savevm_state.handlers, entry, new_se)  \
        if (savevm_state.mode & mask)

Callers:
  SAVEVM_FOR(se, entry, mode_mask(se))
  SAVEVM_FOR(se, entry, VMS_MODE_ALL)
  SAVEVM_FOR_SAFE(se, entry, mode_mask(se))
  SAVEVM_FOR_SAFE(se, entry, VMS_MODE_ALL)

- Steve

>>  static bool should_validate_capability(int capability)
>>  {
>>      assert(capability >= 0 && capability < MIGRATION_CAPABILITY__MAX);
>> @@ -673,7 +692,7 @@ static uint32_t calculate_new_instance_id(const char 
>> *idstr)
>>      SaveStateEntry *se;
>>      uint32_t instance_id = 0;
>>  
>> -    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>> +    SAVEVM_FORALL(se, entry) {
>>          if (strcmp(idstr, se->idstr) == 0
>>              && instance_id <= se->instance_id) {
>>              instance_id = se->instance_id + 1;
>> @@ -689,7 +708,7 @@ static int calculate_compat_instance_id(const char 
>> *idstr)
>>      SaveStateEntry *se;
>>      int instance_id = 0;
>>  
>> -    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>> +    SAVEVM_FORALL(se, entry) {
>>          if (!se->compat) {
>>              continue;
>>          }
>> @@ -803,7 +822,7 @@ void unregister_savevm(VMStateIf *obj, const char 
>> *idstr, void *opaque)
>>      }
>>      pstrcat(id, sizeof(id), idstr);
>>  
>> -    QTAILQ_FOREACH_SAFE(se, &savevm_state.handlers, entry, new_se) {
>> +    SAVEVM_FORALL_SAFE(se, entry, new_se) {
>>          if (strcmp(se->idstr, id) == 0 && se->opaque == opaque) {
>>              savevm_state_handler_remove(se);
>>              g_free(se->compat);
>> @@ -867,7 +886,7 @@ void vmstate_unregister(VMStateIf *obj, const 
>> VMStateDescription *vmsd,
>>  {
>>      SaveStateEntry *se, *new_se;
>>  
>> -    QTAILQ_FOREACH_SAFE(se, &savevm_state.handlers, entry, new_se) {
>> +    SAVEVM_FORALL_SAFE(se, entry, new_se) {
>>          if (se->vmsd == vmsd && se->opaque == opaque) {
>>              savevm_state_handler_remove(se);
>>              g_free(se->compat);
>> @@ -1119,7 +1138,7 @@ bool qemu_savevm_state_blocked(Error **errp)
>>  {
>>      SaveStateEntry *se;
>>  
>> -    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>> +    SAVEVM_FORALL(se, entry) {
>>          if (se->vmsd && se->vmsd->unmigratable) {
>>              error_setg(errp, "State blocked by non-migratable device '%s'",
>>                         se->idstr);
>> @@ -1145,7 +1164,7 @@ bool qemu_savevm_state_guest_unplug_pending(void)
>>  {
>>      SaveStateEntry *se;
>>  
>> -    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>> +    SAVEVM_FOREACH(se, entry) {
>>          if (se->vmsd && se->vmsd->dev_unplug_pending &&
>>              se->vmsd->dev_unplug_pending(se->opaque)) {
>>              return true;
>> @@ -1162,7 +1181,7 @@ void qemu_savevm_state_setup(QEMUFile *f)
>>      int ret;
>>  
>>      trace_savevm_state_setup();
>> -    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>> +    SAVEVM_FOREACH(se, entry) {
>>          if (!se->ops || !se->ops->save_setup) {
>>              continue;
>>          }
>> @@ -1193,7 +1212,7 @@ int qemu_savevm_state_resume_prepare(MigrationState *s)
>>  
>>      trace_savevm_state_resume_prepare();
>>  
>> -    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>> +    SAVEVM_FOREACH(se, entry) {
>>          if (!se->ops || !se->ops->resume_prepare) {
>>              continue;
>>          }
>> @@ -1223,7 +1242,7 @@ int qemu_savevm_state_iterate(QEMUFile *f, bool 
>> postcopy)
>>      int ret = 1;
>>  
>>      trace_savevm_state_iterate();
>> -    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>> +    SAVEVM_FOREACH(se, entry) {
>>          if (!se->ops || !se->ops->save_live_iterate) {
>>              continue;
>>          }
>> @@ -1291,7 +1310,7 @@ void qemu_savevm_state_complete_postcopy(QEMUFile *f)
>>      SaveStateEntry *se;
>>      int ret;
>>  
>> -    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>> +    SAVEVM_FOREACH(se, entry) {
>>          if (!se->ops || !se->ops->save_live_complete_postcopy) {
>>              continue;
>>          }
>> @@ -1324,7 +1343,7 @@ int 
>> qemu_savevm_state_complete_precopy_iterable(QEMUFile *f, bool in_postcopy)
>>      SaveStateEntry *se;
>>      int ret;
>>  
>> -    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>> +    SAVEVM_FOREACH(se, entry) {
>>          if (!se->ops ||
>>              (in_postcopy && se->ops->has_postcopy &&
>>               se->ops->has_postcopy(se->opaque)) ||
>> @@ -1366,7 +1385,7 @@ int 
>> qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f,
>>      vmdesc = qjson_new();
>>      json_prop_int(vmdesc, "page_size", qemu_target_page_size());
>>      json_start_array(vmdesc, "devices");
>> -    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>> +    SAVEVM_FOREACH(se, entry) {
>>  
>>          if ((!se->ops || !se->ops->save_state) && !se->vmsd) {
>>              continue;
>> @@ -1476,7 +1495,7 @@ void qemu_savevm_state_pending(QEMUFile *f, uint64_t 
>> threshold_size,
>>      *res_postcopy_only = 0;
>>  
>>  
>> -    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>> +    SAVEVM_FOREACH(se, entry) {
>>          if (!se->ops || !se->ops->save_live_pending) {
>>              continue;
>>          }
>> @@ -1501,7 +1520,7 @@ void qemu_savevm_state_cleanup(void)
>>      }
>>  
>>      trace_savevm_state_cleanup();
>> -    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>> +    SAVEVM_FOREACH(se, entry) {
>>          if (se->ops && se->ops->save_cleanup) {
>>              se->ops->save_cleanup(se->opaque);
>>          }
>> @@ -1580,7 +1599,7 @@ int qemu_save_device_state(QEMUFile *f)
>>      }
>>      cpu_synchronize_all_states();
>>  
>> -    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>> +    SAVEVM_FOREACH(se, entry) {
>>          int ret;
>>  
>>          if (se->is_ram) {
>> @@ -1612,7 +1631,7 @@ static SaveStateEntry *find_se(const char *idstr, 
>> uint32_t instance_id)
>>  {
>>      SaveStateEntry *se;
>>  
>> -    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>> +    SAVEVM_FORALL(se, entry) {
>>          if (!strcmp(se->idstr, idstr) &&
>>              (instance_id == se->instance_id ||
>>               instance_id == se->alias_id))
>> @@ -2334,7 +2353,7 @@ qemu_loadvm_section_part_end(QEMUFile *f, 
>> MigrationIncomingState *mis)
>>      }
>>  
>>      trace_qemu_loadvm_state_section_partend(section_id);
>> -    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>> +    SAVEVM_FOREACH(se, entry) {
>>          if (se->load_section_id == section_id) {
>>              break;
>>          }
>> @@ -2400,7 +2419,7 @@ static int qemu_loadvm_state_setup(QEMUFile *f)
>>      int ret;
>>  
>>      trace_loadvm_state_setup();
>> -    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>> +    SAVEVM_FOREACH(se, entry) {
>>          if (!se->ops || !se->ops->load_setup) {
>>              continue;
>>          }
>> @@ -2425,7 +2444,7 @@ void qemu_loadvm_state_cleanup(void)
>>      SaveStateEntry *se;
>>  
>>      trace_loadvm_state_cleanup();
>> -    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>> +    SAVEVM_FOREACH(se, entry) {
>>          if (se->ops && se->ops->load_cleanup) {
>>              se->ops->load_cleanup(se->opaque);
>>          }
>> -- 
>> 1.8.3.1
>>