Re: [Qemu-devel] [PATCH v3 8/9] vmstate: Add preallocation for migrating arrays (VMS_ALLOC flag)

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 06/03/2014 11:19 PM, Alexey Kardashevskiy wrote:
> On 05/30/2014 07:34 PM, Alexey Kardashevskiy wrote:
>> There are few helpers already to support array migration. However they all
>> require the destination side to preallocate arrays before migration which
>> is not always possible due to unknown array size as it might be some
>> sort of dynamic state. One of the examples is an array of MSIX-enabled
>> devices in SPAPR PHB - this array may vary from 0 to 65536 entries and
>> its size depends on guest's ability to enable MSIX or do PCI hotplug.
>>
>> This adds new VMSTATE_VARRAY_STRUCT_ALLOC macro which is pretty similar to
>> VMSTATE_STRUCT_VARRAY_POINTER_INT32 but it can alloc memory for migratign
>> array on the destination side.
>>
>> This defines VMS_ALLOC flag for a field.
>>
>> This changes vmstate_base_addr() to do the allocation when receiving
>> migration.
> 
> 
> 
> Juan, Peter? No hurry, just pinging in order not to forget :) Thanks!


Hi, anyone? :)



> 
> 
>>
>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>> ---
>>  include/migration/vmstate.h | 11 +++++++++++
>>  vmstate.c                   | 13 ++++++++++---
>>  2 files changed, 21 insertions(+), 3 deletions(-)
>>
>> diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
>> index 7e45048..e794694 100644
>> --- a/include/migration/vmstate.h
>> +++ b/include/migration/vmstate.h
>> @@ -101,6 +101,7 @@ enum VMStateFlags {
>>      VMS_VARRAY_UINT8     = 0x400,  /* Array with size in uint8_t field*/
>>      VMS_VARRAY_UINT32    = 0x800,  /* Array with size in uint32_t field*/
>>      VMS_MUST_EXIST       = 0x1000, /* Field must exist in input */
>> +    VMS_ALLOC            = 0x2000, /* Alloc a buffer on the destination */
>>  };
>>  
>>  typedef struct {
>> @@ -429,6 +430,16 @@ extern const VMStateInfo vmstate_info_bitmap;
>>      .offset     = offsetof(_state, _field),                          \
>>  }
>>  
>> +#define VMSTATE_STRUCT_VARRAY_ALLOC(_field, _state, _field_num, _version, _vmsd, _type) {\
>> +    .name       = (stringify(_field)),                               \
>> +    .version_id = (_version),                                        \
>> +    .vmsd       = &(_vmsd),                                          \
>> +    .num_offset = vmstate_offset_value(_state, _field_num, int32_t), \
>> +    .size       = sizeof(_type),                                     \
>> +    .flags      = VMS_STRUCT|VMS_VARRAY_INT32|VMS_ALLOC|VMS_POINTER, \
>> +    .offset     = vmstate_offset_pointer(_state, _field, _type),     \
>> +}
>> +
>>  #define VMSTATE_STATIC_BUFFER(_field, _state, _version, _test, _start, _size) { \
>>      .name         = (stringify(_field)),                             \
>>      .version_id   = (_version),                                      \
>> diff --git a/vmstate.c b/vmstate.c
>> index b5882fa..fb95e39 100644
>> --- a/vmstate.c
>> +++ b/vmstate.c
>> @@ -43,11 +43,18 @@ static int vmstate_size(void *opaque, VMStateField *field)
>>      return size;
>>  }
>>  
>> -static void *vmstate_base_addr(void *opaque, VMStateField *field)
>> +static void *vmstate_base_addr(void *opaque, VMStateField *field, bool alloc)
>>  {
>>      void *base_addr = opaque + field->offset;
>>  
>>      if (field->flags & VMS_POINTER) {
>> +        if (alloc && (field->flags & VMS_ALLOC)) {
>> +            int n_elems = vmstate_n_elems(opaque, field);
>> +            if (n_elems) {
>> +                *((void **)base_addr + field->start) = g_malloc_n(n_elems,
>> +                                                                  field->size);
>> +            }
>> +        }
>>          base_addr = *(void **)base_addr + field->start;
>>      }
>>  
>> @@ -81,7 +88,7 @@ int vmstate_load_state(QEMUFile *f, const VMStateDescription *vmsd,
>>               field->field_exists(opaque, version_id)) ||
>>              (!field->field_exists &&
>>               field->version_id <= version_id)) {
>> -            void *base_addr = vmstate_base_addr(opaque, field);
>> +            void *base_addr = vmstate_base_addr(opaque, field, true);
>>              int i, n_elems = vmstate_n_elems(opaque, field);
>>              int size = vmstate_size(opaque, field);
>>  
>> @@ -131,7 +138,7 @@ void vmstate_save_state(QEMUFile *f, const VMStateDescription *vmsd,
>>      while (field->name) {
>>          if (!field->field_exists ||
>>              field->field_exists(opaque, vmsd->version_id)) {
>> -            void *base_addr = vmstate_base_addr(opaque, field);
>> +            void *base_addr = vmstate_base_addr(opaque, field, false);
>>              int i, n_elems = vmstate_n_elems(opaque, field);
>>              int size = vmstate_size(opaque, field);
>>  
>>
> 
> 


-- 
Alexey