Re: [kvm-unit-tests PATCH 5/9] lib: s390x: uv: Add UVC_ERR_DEBUG switch

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Wed, 22 Sep 2021 07:18:07 +0000
Janosch Frank <frankja@linux.ibm.com> wrote:

> Every time something goes wrong in a way we don't expect, we need to
> add debug prints to some UVC to get the unexpected return code.
> 
> Let's just put the printing behind a macro so we can enable it if
> needed via a simple switch.
> 
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

but see a nit below

> ---
>  lib/s390x/asm/uv.h | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/lib/s390x/asm/uv.h b/lib/s390x/asm/uv.h
> index 2f099553..0e958ad7 100644
> --- a/lib/s390x/asm/uv.h
> +++ b/lib/s390x/asm/uv.h
> @@ -12,6 +12,9 @@
>  #ifndef _ASMS390X_UV_H_
>  #define _ASMS390X_UV_H_
>  
> +/* Enables printing of command code and return codes for failed UVCs
> */ +#define UVC_ERR_DEBUG	0
> +
>  #define UVC_RC_EXECUTED		0x0001
>  #define UVC_RC_INV_CMD		0x0002
>  #define UVC_RC_INV_STATE	0x0003
> @@ -194,6 +197,15 @@ static inline int uv_call_once(unsigned long r1,
> unsigned long r2) : [cc] "=d" (cc)
>  		: [r1] "a" (r1), [r2] "a" (r2)
>  		: "memory", "cc");
> +
> +#if UVC_ERR_DEBUG
> +	if (cc)

it probably looks cleaner like this:

	if (UVC_ERR_DEBUG && cc)

and without the #if; the compiler should be smart enough to remove the
dead code. In practice it doesn't really matter in the end, so feel free
to ignore this comment :)

> +		printf("UV call error: call %x rc %x rrc %x\n",
> +		       ((struct uv_cb_header *)r2)->cmd,
> +		       ((struct uv_cb_header *)r2)->rc,
> +		       ((struct uv_cb_header *)r2)->rrc);
> +#endif
> +
>  	return cc;
>  }
>