Re: [PATCH v1 1/2] s390/cpacf: Rework cpacf_kma() to return condition code

[Heiko Carstens <hca@linux.ibm.com>]

On Tue, Oct 06, 2026 at 03:29:28PM +0200, Harald Freudenberger wrote:
> On 2026-10-06 10:30, Heiko Carstens wrote:
> > On Mon, Oct 05, 2026 at 04:14:15PM +0200, Harald Freudenberger wrote:
> > ...
> > > better readability. Additionally add an kmsan_unpoison_memory()
> > > statement to reflect the updated memory by hardware.
> > ...
> > > @@ -731,12 +739,16 @@ static inline void cpacf_kma(unsigned long
> > > func, void *param, u8 *dest,
> > >  		"	lgr	0,%[fc]\n"
> > >  		"	lgr	1,%[pba]\n"
> > >  		"0:	.insn	rrf,%[opc] << 16,%[dst],%[src],%[aad],0\n"
> > > -		"	brc	1,0b"	/* handle partial completion */
> > > -		: [dst] "+&d" (d.pair), [src] "+&d" (s.pair),
> > > +		"	brc	1,0b\n"	/* handle partial completion */
> > > +		CC_IPM(cc)
> > > +		: CC_OUT(cc, cc), [dst] "+&d" (d.pair), [src] "+&d" (s.pair),
> > >  		  [aad] "+&d" (a.pair)
> > >  		: [fc] "d" (func), [pba] "d" ((unsigned long)param),
> > >  		  [opc] "i" (CPACF_KMA)
> > > -		: "cc", "memory", "0", "1");
> > > +		: CC_CLOBBER_LIST("memory", "0", "1"));
> > > +
> > > +	kmsan_unpoison_memory(dest, src_len - s.odd);
> > 
> > Since you added explicit instrumentation here it would sense so add
> > kasan/kcsan instrumentation by adding an instrument_write() call.

That should have been "...it would make sense to..."

> I have no idea what you mean here...

See include/linux/instrumented.h - you can the kernel about
memory accesses also kasan and kcsan. Your patch only adds
that for kmsan. See arch/s390/include/asm/fpu-insn.h for many
examples. I'm aware that such annotations are currently missing
for many of our inline asms. But since you are at it.

Up to you if you want to add it or not. Just a suggestion.

> > Also, given that this is in-kernel crypto, shouldn't this series go
> > via the crypto tree?
> 
> Well, this is to be negotiated. I first wanted to collect an RB statement.

It would be helpful if you would add information like that in the
cover-letter. This saves both of us a bit of time.