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

[Alexey Kardashevskiy <aik@ozlabs.ru>]

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!


> 
> 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