Re: [kvm-unit-tests PATCH 8/9] s390x: Add sthyi cc==0 r2+1 verification

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

On Wed, 22 Sep 2021 07:18:10 +0000
Janosch Frank <frankja@linux.ibm.com> wrote:

> On success r2 + 1 should be 0, let's also check for that.
> 
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>

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

but see comment below

> ---
>  s390x/sthyi.c | 20 +++++++++++---------
>  1 file changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/s390x/sthyi.c b/s390x/sthyi.c
> index db90b56f..4b153bf4 100644
> --- a/s390x/sthyi.c
> +++ b/s390x/sthyi.c
> @@ -24,16 +24,16 @@ static inline int sthyi(uint64_t vaddr, uint64_t fcode, uint64_t *rc,
>  {
>  	register uint64_t code asm("0") = fcode;
>  	register uint64_t addr asm("2") = vaddr;
> -	register uint64_t rc3 asm("3") = 0;
> +	register uint64_t rc3 asm("3") = 42;

I am not a big fan of the asm constraints, in the kernel we are
trying to move away from them, but I guess as long as it works it's ok

>  	int cc = 0;
>  
> -	asm volatile(".insn rre,0xB2560000,%[r1],%[r2]\n"
> -		     "ipm	 %[cc]\n"
> -		     "srl	 %[cc],28\n"
> -		     : [cc] "=d" (cc)
> -		     : [code] "d" (code), [addr] "a" (addr), [r1] "i" (r1),
> -		       [r2] "i" (r2)
> -		     : "memory", "cc", "r3");
> +	asm volatile(
> +		".insn   rre,0xB2560000,%[r1],%[r2]\n"
> +		"ipm     %[cc]\n"
> +		"srl     %[cc],28\n"
> +		: [cc] "=d" (cc), "+d" (rc3)
> +		: [code] "d" (code), [addr] "a" (addr), [r1] "i" (r1), [r2] "i" (r2)
> +		: "memory", "cc");
>  	if (rc)
>  		*rc = rc3;
>  	return cc;
> @@ -139,16 +139,18 @@ static void test_fcode0(void)
>  	struct sthyi_hdr_sctn *hdr;
>  	struct sthyi_mach_sctn *mach;
>  	struct sthyi_par_sctn *par;
> +	uint64_t rc = 42;
>  
>  	/* Zero destination memory. */
>  	memset(pagebuf, 0, PAGE_SIZE);
>  
>  	report_prefix_push("fcode 0");
> -	sthyi((uint64_t)pagebuf, 0, NULL, 0, 2);
> +	sthyi((uint64_t)pagebuf, 0, &rc, 0, 2);
>  	hdr = (void *)pagebuf;
>  	mach = (void *)pagebuf + hdr->INFMOFF;
>  	par = (void *)pagebuf + hdr->INFPOFF;
>  
> +	report(!rc, "r2 + 1 == 0");
>  	test_fcode0_hdr(hdr);
>  	test_fcode0_mach(mach);
>  	test_fcode0_par(par);