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

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On 2019-12-02 19:15, Cornelia Huck wrote:
On Mon, 2 Dec 2019 18:53:16 +0100
Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote:

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

So the the subchannel are always one after the other?



+		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.

Would never happend to me.




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?

yes, so I must think about this



+	}
+	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 :)

yes, found is too much.
A cut and past from the time I was happy to find even one! :)


+		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 :)


Thanks,

Regards,
Pierre

--
Pierre Morel
IBM Lab Boeblingen




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