Re: [PATCH v3 1/4] s390x/css: Introduce an ESW struct

[Cornelia Huck <cohuck@redhat.com>]

On Wed, Jun 16 2021, Eric Farman <farman@linux.ibm.com> wrote:

> The Interrupt Response Block is comprised of several other
> structures concatenated together, but only the 12-byte
> Subchannel-Status Word (SCSW) is defined as a proper struct.
> Everything else is a simple array of 32-bit words.
>
> Let's define a proper struct for the 20-byte Extended-Status
> Word (ESW) so that we can make good decisions about the sense
> data that would go into the ECW area for virtual vs
> passthrough devices.
>
> Signed-off-by: Eric Farman <farman@linux.ibm.com>
> ---
>  hw/s390x/css.c            | 19 +++++++++++++------
>  include/hw/s390x/ioinst.h | 12 +++++++++++-
>  2 files changed, 24 insertions(+), 7 deletions(-)
>

(...)

> diff --git a/include/hw/s390x/ioinst.h b/include/hw/s390x/ioinst.h
> index c6737a30d4..9613e0ccbb 100644
> --- a/include/hw/s390x/ioinst.h
> +++ b/include/hw/s390x/ioinst.h
> @@ -123,10 +123,20 @@ typedef struct SCHIB {
>      uint8_t mda[4];
>  } QEMU_PACKED SCHIB;
>  
> +/* extended-status word */
> +typedef struct ESW {
> +   uint32_t sublog;
> +   uint32_t erw;
> +   uint64_t f_addr;
> +   uint32_t s_addr;
> +} QEMU_PACKED ESW;

Strictly speaking, that's a format 0 esw. Doesn't matter too much in the
end, I think:
- erw is always the same
- f_addr and s_addr are always 0 for the other formats
- 'sublog' is always a u32 with the lpum in the same place (which we
  always set to 0x80 for virtual subchannels, as they have only one path)

> +
> +#define ESW_ERW_SENSE 0x01000000
> +
>  /* interruption response block */
>  typedef struct IRB {
>      SCSW scsw;
> -    uint32_t esw[5];
> +    ESW esw;
>      uint32_t ecw[8];
>      uint32_t emw[8];
>  } IRB;