Re: [kvm-unit-tests PATCH v5 1/2] s390x: Add specification exception test

[Janis Schoetterl-Glausch <scgl@linux.ibm.com>]

On Wed, 2022-08-24 at 11:35 +0200, Janosch Frank wrote:
> On 7/20/22 16:25, Janis Schoetterl-Glausch wrote:
> > Generate specification exceptions and check that they occur.
> > 
> > Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
> > ---
> >   s390x/Makefile           |   1 +
> >   lib/s390x/asm/arch_def.h |   5 ++
> >   s390x/spec_ex.c          | 180 +++++++++++++++++++++++++++++++++++++++
> >   s390x/unittests.cfg      |   3 +
> >   4 files changed, 189 insertions(+)
> >   create mode 100644 s390x/spec_ex.c
> > 
> > 
> > +
> > +/*
> > + * Load possibly invalid psw, but setup fixup_psw before,
> > + * so that fixup_invalid_psw() can bring us back onto the right track.
> > + * Also acts as compiler barrier, -> none required in expect/check_invalid_psw
> > + */
> > +static void load_psw(struct psw psw)
> > +{
> > +	uint64_t scratch;
> > +

[...]

> /*
> Store a valid mask and the address of the nop into the fixup PSW.
> Then load the possibly invalid PSW.
> */

This seems a bit redundant given the function comment, but I can
drop a comment in here describing how the fixup psw is computed.

> 
> > +	fixup_psw.mask = extract_psw_mask();
> > +	asm volatile ( "larl	%[scratch],0f\n"
> > +		"	stg	%[scratch],%[addr]\n"
> > +		"	lpswe	%[psw]\n"
> > +		"0:	nop\n"
> > +		: [scratch] "=&d"(scratch),
> > +		  [addr] "=&T"(fixup_psw.addr)
> 
> s/addr/psw_addr/ ?
> 
> > +		: [psw] "Q"(psw)
> > +		: "cc", "memory"
> > +	);
> > +}
> > +
> > +static void load_short_psw(struct short_psw psw)
> > +{
> > +	uint64_t scratch;
> > +
> > +	fixup_psw.mask = extract_psw_mask();
> > +	asm volatile ( "larl	%[scratch],0f\n"
> > +		"	stg	%[scratch],%[addr]\n"
> > +		"	lpsw	%[psw]\n"
> > +		"0:	nop\n"
> > +		: [scratch] "=&d"(scratch),
> > +		  [addr] "=&T"(fixup_psw.addr)
> > +		: [psw] "Q"(psw)
> > +		: "cc", "memory"
> > +	);
> 
> Same story.

Do you want me to repeat the comments here or just rename addr?

[...]

> > +static int not_even(void)
> > +{
> > +	uint64_t quad[2] __attribute__((aligned(16))) = {0};
> > +
> > +	asm volatile (".insn	rxy,0xe3000000008f,%%r7,%[quad]" /* lpq %%r7,%[quad] */
> > +		      : : [quad] "T"(quad)
> 
> Is there a reason you never put a space after the constraint?

TBH I never noticed I'm unusual in that regard. I guess I tend to think
of the operand and constraint as one entity.
I'll add the spaces.

> 
> > +		      : "%r7", "%r8"
> > +	);
> > +	return 0;
> > +}
> > +

[...]