Re: [kvm-unit-tests PATCH v11 8/9] s390x: css: msch, enable test

Cornelia Huck
2020-07-09T11:41:09Z

On Thu, 9 Jul 2020 10:07:47 +0200
Pierre Morel <pmorel@linux.ibm.com> wrote:

> A second step when testing the channel subsystem is to prepare a channel
> for use.
> This includes:
> - Get the current subchannel Information Block (SCHIB) using STSCH
> - Update it in memory to set the ENABLE bit and the specified ISC
> - Tell the CSS that the SCHIB has been modified using MSCH
> - Get the SCHIB from the CSS again to verify that the subchannel is
> enabled and uses the specified ISC.
> - If the command succeeds but subchannel is not enabled or the ISC
> field is not as expected, retry a predefined retries count.
> - If the command fails, report the failure and do not retry, even
> if cc indicates a busy/status pending as we do not expect this.
>
> This tests the MSCH instruction to enable a channel successfully.
> Retries are done and in case of error, and if the retries count
> is exceeded, a report is made.
>
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> Acked-by: Thomas Huth <thuth@redhat.com>
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
> ---
> lib/s390x/css.h | 8 +++--
> lib/s390x/css_lib.c | 72 +++++++++++++++++++++++++++++++++++++++++++++
> s390x/css.c | 15 ++++++++++
> 3 files changed, 92 insertions(+), 3 deletions(-)

(...)

> +/*
> + * css_msch: enable subchannel and set with specified ISC

"css_enable: enable the subchannel with the specified ISC"

?

> + * @schid: Subchannel Identifier
> + * @isc : number of the interruption subclass to use
> + * Return value:
> + * On success: 0
> + * On error the CC of the faulty instruction
> + * or -1 if the retry count is exceeded.
> + */
> +int css_enable(int schid, int isc)
> +{
> + struct pmcw *pmcw = &schib.pmcw;
> + int retry_count = 0;
> + uint16_t flags;
> + int cc;
> +
> + /* Read the SCHIB for this subchannel */
> + cc = stsch(schid, &schib);
> + if (cc) {
> + report_info("stsch: sch %08x failed with cc=%d", schid, cc);
> + return cc;
> + }
> +
> + flags = PMCW_ENABLE | (isc << PMCW_ISC_SHIFT);
> + if ((pmcw->flags & flags) == flags) {

I think you want (pmcw->flags & PMCW_ENABLE) == PMCW_ENABLE -- this
catches the case of "subchannel has been enabled before, but with a
different isc".

> + report_info("stsch: sch %08x already enabled", schid);
> + return 0;
> + }

(...)