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

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On 2019-12-02 20:49, Cornelia Huck wrote:
On Mon, 2 Dec 2019 19:33:59 +0100
Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote:

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?

While QEMU (and z/VM) usually do that, they can really be scattered
around. For the in-between I/O subchannels that don't lead to a device,
you'll still get cc 0, it's just the dnv bit that is 0. The cc 3
basically just tells you that you can stop looking.


Thanks for the explanation, I will change the code accordingly.

Regards,
Pierre

--
Pierre Morel
IBM Lab Boeblingen




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