Re: [kvm-unit-tests PATCH v3 14/16] s390x: css: issuing SSCH when the channel is status pending

[Cornelia Huck <cohuck@redhat.com>]

On Tue,  6 Apr 2021 09:40:51 +0200
Pierre Morel <pmorel@linux.ibm.com> wrote:

> We await CC=1 when we issue a SSCH on a channel with status pending.
> 
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> ---
>  lib/s390x/css.h |  2 ++
>  s390x/css.c     | 10 ++++++++++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/lib/s390x/css.h b/lib/s390x/css.h
> index 08b2974..3eb6957 100644
> --- a/lib/s390x/css.h
> +++ b/lib/s390x/css.h
> @@ -90,6 +90,8 @@ struct scsw {
>  #define SCSW_ESW_FORMAT		0x04000000
>  #define SCSW_SUSPEND_CTRL	0x08000000
>  #define SCSW_KEY		0xf0000000
> +#define SCSW_SSCH_COMPLETED	(SCSW_CCW_FORMAT | SCSW_FC_START | SCSW_SC_PENDING | SCSW_SC_SECONDARY | \
> +				 SCSW_SC_PRIMARY)
>  	uint32_t ctrl;
>  	uint32_t ccw_addr;
>  #define SCSW_DEVS_DEV_END	0x04
> diff --git a/s390x/css.c b/s390x/css.c
> index f8c6688..52264f2 100644
> --- a/s390x/css.c
> +++ b/s390x/css.c
> @@ -258,6 +258,15 @@ static void ssch_orb_fcx(void)
>  	orb->ctrl = tmp;
>  }
>  
> +static void ssch_status_pending(void)
> +{
> +	assert(ssch(test_device_sid, orb) == 0);
> +	report(ssch(test_device_sid, orb) == 1, "CC = 1");

I don't think that's correct in the general case (although it will work
for QEMU).

The PoP has a note about some models discarding the status pending, if
we have secondary status only (although I don't think that would happen
with this sequence.) You might also end up with cc 2 here, I think. In
theory, you could also get a cc 3 on real hardware, but that would be a
real edge case, and subsequent tests would fail anyway.

> +	/* now we clear the status */
> +	assert(tsch(test_device_sid, &irb) == 0);
> +	check_io_completion(test_device_sid, SCSW_SSCH_COMPLETED);
> +}
> +
>  static struct tests ssh_tests[] = {
>  	{ "privilege", ssch_privilege },
>  	{ "orb cpa zero", ssch_orb_cpa_zero },
> @@ -269,6 +278,7 @@ static struct tests ssh_tests[] = {
>  	{ "ORB reserved CTRL bits", ssch_orb_ctrl },
>  	{ "ORB extensions", ssch_orb_extension},
>  	{ "FC extensions", ssch_orb_fcx},
> +	{ "status pending before ssch", ssch_status_pending},
>  	{ NULL, NULL }
>  };
>