[Qemu-devel] Re: [PATCH 1/6] Make fw_cfg interface 32-bit aware

[Glauber Costa]

On Thu, Nov 12, 2009 at 09:53:10PM +0100, Alexander Graf wrote:
> The fw_cfg interface can only handle up to 16 bits of data for its streams.
> While that isn't too much of a problem when handling integers, we would
> like to stream full kernel images over that interface!
> 
> So let's extend it to 32 bit length variables.
> 
> Signed-off-by: Alexander Graf <address@hidden>
> 
> ---
> 
> v1 -> v2:
> 
>   - add savevm compat code (untested!)
> ---
>  hw/fw_cfg.c |   30 ++++++++++++++++++++++++------
>  hw/fw_cfg.h |    2 +-
>  2 files changed, 25 insertions(+), 7 deletions(-)
> 
> diff --git a/hw/fw_cfg.c b/hw/fw_cfg.c
> index a6d811b..0cd6f68 100644
> --- a/hw/fw_cfg.c
> +++ b/hw/fw_cfg.c
> @@ -39,7 +39,7 @@
>  #define FW_CFG_SIZE 2
>  
>  typedef struct _FWCfgEntry {
> -    uint16_t len;
> +    uint32_t len;
>      uint8_t *data;
>      void *callback_opaque;
>      FWCfgCallback callback;
> @@ -48,7 +48,7 @@ typedef struct _FWCfgEntry {
>  typedef struct _FWCfgState {
>      FWCfgEntry entries[2][FW_CFG_MAX_ENTRY];
>      uint16_t cur_entry;
> -    uint16_t cur_offset;
> +    uint32_t cur_offset;
>  } FWCfgState;
>  
>  static void fw_cfg_write(FWCfgState *s, uint8_t value)
> @@ -164,19 +164,37 @@ static void fw_cfg_reset(void *opaque)
>      fw_cfg_select(s, 0);
>  }
>  
> +static int fw_cfg_load_old(QEMUFile *f, void *opaque, int version_id)
> +{
> +    FWCfgState *s = opaque;
> +    uint16_t cur_offset;
> +
> +    if (version_id != 1)
> +        return -EINVAL;
> +
> +    qemu_get_be16s(f, &s->cur_entry);
> +
> +    /* Convert old 16 bit value to new 32 bit width */
> +    qemu_get_be16s(f, &cur_offset);
> +    s->cur_offset = cur_offset;
> +
> +    return 0;
> +}
> +
>  static const VMStateDescription vmstate_fw_cfg = {
>      .name = "fw_cfg",
> -    .version_id = 1,
> -    .minimum_version_id = 1,
> +    .version_id = 2,
> +    .minimum_version_id = 2,
>      .minimum_version_id_old = 1,
> +    .load_state_old = fw_cfg_load_old,
>      .fields      = (VMStateField []) {
>          VMSTATE_UINT16(cur_entry, FWCfgState),
> -        VMSTATE_UINT16(cur_offset, FWCfgState),
> +        VMSTATE_UINT32(cur_offset, FWCfgState),
>          VMSTATE_END_OF_LIST()
>      }
>  };

Why don't we just add another field for the upper bits, and add it through
VMSTATE_UINT16_V ?