Re: [Qemu-devel] [PATCH v2 2/8] s390x/css: IO instr handler ending control

[Thomas Huth <thuth@redhat.com>]

On 04.10.2017 17:41, Halil Pasic wrote:
> CSS code needs to tell the IO instruction handlers located in how should

located in how?

> the emulated instruction be ended. Currently this is done by returning
> generic (POSIX) error codes, and mapping them to outcomes like condition
> codes. This makes bugs easy to create and hard to recognise.
> 
> As a preparation for moving a way form (mis)using generic error codes for
> flow control let us introduce a struct which tells the instruction
> handler function how to end the instruction, in a more straight-forward
> and less ambiguous way.
> 
> Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com>
> ---
>  include/hw/s390x/css.h | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/include/hw/s390x/css.h b/include/hw/s390x/css.h
> index 0653d3c9be..66916b6546 100644
> --- a/include/hw/s390x/css.h
> +++ b/include/hw/s390x/css.h
> @@ -75,6 +75,18 @@ typedef struct CMBE {
>      uint32_t reserved[7];
>  } QEMU_PACKED CMBE;
>  
> +/* IO instructions conclude according this */
> +typedef struct IOInstEnding {
> +        /*
> +         * General semantic of cc codes of IO instructions is (brief):
> +         * 0 -- produced expected result
> +         * 1 --  status conditions were present or produced alternate result
> +         * 2 -- ineffective, because busy with previously initiated function
> +         * 3 -- ineffective, not operational
> +         */
> +        int cc;
> +} IOInstEnding;

Why do you need a struct for this? Do you plan to extend it later? If
so, I think you should mention that in the patch description. If not,
please use a named enum or a "typedef unsigned int IOInstEnding" instead.

 Thomas