Re: [kvm-unit-tests PATCH v7 09/12] s390x: css: msch, enable test

[Cornelia Huck <cohuck@redhat.com>]

On Mon, 18 May 2020 18:07:28 +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
> - 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.
> - If the subchannel is not enabled retry a predefined retries count.
> 
> This tests the MSCH instruction to enable a channel succesfuly.
> This is NOT a routine to really enable the channel, no retry is done,
> in case of error, a report is made.

Hm... so you retry if the subchannel is not enabled after cc 0, but you
don't retry if the cc indicates busy/status pending? Makes sense, as we
don't expect the subchannel to be busy, but a more precise note in the
patch description would be good :)

> 
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> ---
>  s390x/css.c | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 67 insertions(+)
> 
> diff --git a/s390x/css.c b/s390x/css.c
> index d7989d8..1b60a47 100644
> --- a/s390x/css.c
> +++ b/s390x/css.c
> @@ -16,6 +16,7 @@
>  #include <string.h>
>  #include <interrupt.h>
>  #include <asm/arch_def.h>
> +#include <asm/time.h>
>  
>  #include <css.h>
>  
> @@ -65,11 +66,77 @@ out:
>  	       scn, scn_found, dev_found);
>  }
>  
> +#define MAX_ENABLE_RETRIES	5
> +static void test_enable(void)
> +{
> +	struct pmcw *pmcw = &schib.pmcw;
> +	int retry_count = 0;
> +	int cc;
> +
> +	if (!test_device_sid) {
> +		report_skip("No device");
> +		return;
> +	}
> +
> +	/* Read the SCHIB for this subchannel */
> +	cc = stsch(test_device_sid, &schib);
> +	if (cc) {
> +		report(0, "stsch cc=%d", cc);
> +		return;
> +	}
> +
> +	if (pmcw->flags & PMCW_ENABLE) {
> +		report(1, "stsch: sch %08x already enabled", test_device_sid);
> +		return;
> +	}
> +
> +retry:
> +	/* Update the SCHIB to enable the channel */
> +	pmcw->flags |= PMCW_ENABLE;
> +
> +	/* Tell the CSS we want to modify the subchannel */
> +	cc = msch(test_device_sid, &schib);
> +	if (cc) {
> +		/*
> +		 * If the subchannel is status pending or
> +		 * if a function is in progress,
> +		 * we consider both cases as errors.

Could also be cc 3, but that would be even more weird. Just logging the
cc seems fine, though.

> +		 */
> +		report(0, "msch cc=%d", cc);
> +		return;
> +	}
> +
> +	/*
> +	 * Read the SCHIB again to verify the enablement
> +	 */
> +	cc = stsch(test_device_sid, &schib);
> +	if (cc) {
> +		report(0, "stsch cc=%d", cc);
> +		return;
> +	}
> +
> +	if (pmcw->flags & PMCW_ENABLE) {
> +		report(1, "msch: sch %08x enabled after %d retries",
> +		       test_device_sid, retry_count);
> +		return;
> +	}
> +
> +	if (retry_count++ < MAX_ENABLE_RETRIES) {
> +		mdelay(10); /* the hardware was not ready, let it some time */

s/let/give/

> +		goto retry;
> +	}
> +
> +	report(0,
> +	       "msch: enabling sch %08x failed after %d retries. pmcw: %x",
> +	       test_device_sid, retry_count, pmcw->flags);
> +}
> +
>  static struct {
>  	const char *name;
>  	void (*func)(void);
>  } tests[] = {
>  	{ "enumerate (stsch)", test_enumerate },
> +	{ "enable (msch)", test_enable },
>  	{ NULL, NULL }
>  };
>  

Otherwise,
Reviewed-by: Cornelia Huck <cohuck@redhat.com>