[Skiboot] [PATCH v8 20/24] MPIPL: Add OPAL API to query saved tags

[Nicholas Piggin]

Vasant Hegde's on June 17, 2019 3:10 am:
> Pre-MPIPL kernel saves various information required to create vmcore in
> metadata area and passes metadata area pointer to OPAL. OPAL will preserve
> this pointer across MPIPL. Post MPIPL kernel will request for saved tags
> via this API. Kernel also needs below tags:
>   - Saved CPU registers data to access CPU registers
>   - OPAL metadata area to create opalcore
> 
> Format:
>   opal_mpipl_query_tag(uint32_t idx, uint64_t *tag)
> 
>   idx : tag index (0..n)
>   tag : OPAL will pass saved tag
> 
>   Kernel will make this call with increased `index` until OPAL returns
>   OPAL_EMPTY.
> 
> Return values:
>   OPAL_SUCCESS   : Operation success
>   OPAL_PARAMETER : Invalid parameter
>   OPAL_EMPTY	 : OPAL completed sending all tags to kernel

Thanks for doing this API as well. I like giving the client the
ability to just define their own metadata in preserved memory.

Thanks,
Nick