Re: [PATCH v3 06/17] hw/sd/sdcard: Do not store vendor data on block drive (CMD56)

[Fabiano Rosas]

Philippe Mathieu-Daudé <philmd@linaro.org> writes:

> "General command" (GEN_CMD, CMD56) is described as:
>
>   GEN_CMD is the same as the single block read or write
>   commands (CMD24 or CMD17). The difference is that [...]
>   the data block is not a memory payload data but has a
>   vendor specific format and meaning.
>
> Thus this block must not be stored overwriting data block
> on underlying storage drive. Keep it in a dedicated
> 'vendor_data[]' array.
>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> Tested-by: Cédric Le Goater <clg@redhat.com>
> ---
> RFC: Is it safe to reuse VMSTATE_UNUSED_V() (which happens
> to be the same size)?

Hi, sorry it took some time to get to this, I had just left for vacation
when you first posted.

I think it's ok:

{
  "field": "unused",
  "version_id": 1,
  "field_exists": false,
  "size": 512
},

vs.

{
  "field": "vendor_data",
  "version_id": 0,
  "field_exists": false,
  "num": 512,
  "size": 1
},

The unused field was introduced in 2016 so there's no chance of
migrating a QEMU that old to/from 9.1.