Re: [kvm-unit-tests PATCH v2 6/9] s390x: css: stsch, enumeration test

Cornelia Huck
2019-12-02T18:16:12Z

On Mon, 2 Dec 2019 18:53:16 +0100
Pierre Morel <pmorel@linux.ibm.com> wrote:

> On 2019-12-02 15:22, Cornelia Huck wrote:
> > On Thu, 28 Nov 2019 13:46:04 +0100
> > Pierre Morel <pmorel@linux.ibm.com> wrote:

> >> +static int test_device_sid;
> >> +
> >> +static void test_enumerate(void)
> >> +{
> >> + struct pmcw *pmcw = &schib.pmcw;
> >> + int sid;
> >> + int ret, i;
> >> + int found = 0;
> >> +
> >> + for (sid = 0; sid < 0xffff; sid++) {
> >> + ret = stsch(sid|SID_ONE, &schib);
> >
> > This seems a bit odd. You are basically putting the subchannel number
> > into sid, OR in the one, and then use the resulting value as the sid
> > (subchannel identifier).
> >
> >> + if (!ret && (pmcw->flags & PMCW_DNV)) {
> >> + report_info("SID %04x Type %s PIM %x", sid,
> >
> > That's not a sid, but the subchannel number (see above).
> >
> >> + Channel_type[pmcw->st], pmcw->pim);
> >> + for (i = 0; i < 8; i++) {
> >> + if ((pmcw->pim << i) & 0x80) {
> >> + report_info("CHPID[%d]: %02x", i,
> >> + pmcw->chpid[i]);
> >> + break;
> >> + }
> >> + }
> >> + found++;
> >> +
> >> + }
> >
> > Here, you iterate over the 0-0xffff range, even if you got a condition
> > code 3 (indicating no more subchannels in that set). Is that
> > intentional?
>
> I thought there could be more subchannels.
> I need then a break in the loop when this happens.
> I will reread the PoP to see how to find that no more subchannel are in
> that set.

The fact that cc 3 for stsch == no more subchannels is unfortunately a
bit scattered across the PoP :/ Dug it out some time ago, maybe it's
still in the archives somewhere...

>
> >
> >> + if (found && !test_device_sid)
> >> + test_device_sid = sid|SID_ONE;
> >
> > You set test_device_sid to the last valid subchannel? Why?
>
> The last ? I wanted the first one

It is indeed the first one, -ENOCOFFEE.

>
> I wanted something easy but I should have explain.
>
> To avoid doing complicated things like doing a sense on each valid
> subchannel I just take the first one.
> Should be enough as we do not go to the device in this test.

Yes; but you plan to reuse that code, don't you?

>
> >
> >> + }
> >> + if (!found) {
> >> + report("Found %d devices", 0, found);

Now that I look at this again: If you got here, you always found 0
devices, so that message is not super helpful :)

> >> + return;
> >> + }
> >> + ret = stsch(test_device_sid, &schib);
> >
> > Why do you do a stsch() again?
>
> right, no need.
> In an internal version I used to print some informations from the SCHIB.
> Since in between I overwrote the SHIB, I did it again.
> But in this version; no need.

You could copy the schib of the subchannel to be tested to a different
place, but I'm not sure it's worth it.

>
> >
> >> + if (ret) {
> >> + report("Err %d on stsch on sid %08x", 0, ret, test_device_sid);
> >> + return;
> >> + }
> >> + report("Tested", 1);
> >> + return;
> >
> > I don't think you need this return statement.
>
> right I have enough work. :)
>
> >
> > Your test only enumerates devices in the first subchannel set. Do you
> > plan to enhance the test to enable the MSS facility and iterate over
> > all subchannel sets?
>
> Yes, it is something we can do in a following series

Sure, just asked out of interest :)