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

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On 2020-07-09 16:22, Cornelia Huck wrote:
On Thu, 9 Jul 2020 15:58:07 +0200
Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote:

On 2020-07-09 15:52, Cornelia Huck wrote:
On Thu, 9 Jul 2020 15:41:56 +0200
Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote:
On 2020-07-09 15:30, Cornelia Huck wrote:
On Thu, 9 Jul 2020 15:12:05 +0200
Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote:
On 2020-07-09 13:40, Cornelia Huck wrote:
On Thu,  9 Jul 2020 10:07:47 +0200
Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote:

(...)
+/*
+ * 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".

If with a different ISC, we need to modify the ISC.
Don't we ?

I think that's a policy decision (I would probably fail and require a
disable before setting another isc, but that's a matter of taste).

Regardless, I think the current check doesn't even catch the 'different
isc' case?

hum, right.
If it is OK I remove this one.
And I must rework the same test I do later
    in this patch.

So, you mean checking for PMCW_ENABLE? Or not at all?

(I'd check for PMCW_ENABLE.)

-       if ((pmcw->flags & flags) == flags) {
+       if ((pmcw->flags & (PMCW_ISC_MASK | PMCW_ENABLE)) == flags) {
                  report_info("stsch: sch %08x already enabled", schid);
                  return 0;
          }

I keep both, otherwise I return 0 without setting the ISC.

Ah, I missed the 'return 0'.

   then I have another error:

   retry:
          /* Update the SCHIB to enable the channel and set the ISC */
+       pmcw->flags &= ~(PMCW_ISC_MASK | PMCW_ENABLE);

Maybe ~PMCW_ISC_MASK is enough?

yes


          pmcw->flags |= flags;

and finaly the same as the first later...

-       if ((pmcw->flags & flags) == flags) {
+       if ((pmcw->flags & (PMCW_ISC_MASK | PMCW_ENABLE)) == flags) {

I think you can keep that as-is.

I don't thing so, I just stored the pmcw.
if ISC is stored as 3 and I want 1 it is a false positive.
Same error as you showed me before.
?


                  report_info("stsch: sch %08x successfully modified
after %d retries",
                              schid, retry_count);


is better I think.
What do you think?

It's probably the right direction.


Thanks,
Pierre

--
Pierre Morel
IBM Lab Boeblingen



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