Re: [kvm-unit-tests PATCH v10 9/9] s390x: css: ssch/tsch with sense and interrupt

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On 2020-07-06 11:46, Cornelia Huck wrote:
On Thu,  2 Jul 2020 18:31:20 +0200
Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote:

After a channel is enabled we start a SENSE_ID command using
the SSCH instruction to recognize the control unit and device.

This tests the success of SSCH, the I/O interruption and the TSCH
instructions.

The SENSE_ID command response is tested to report 0xff inside
its reserved field and to report the same control unit type
as the cu_type kernel argument.

Without the cu_type kernel argument, the test expects a device
with a default control unit type of 0x3832, a.k.a virtio-net-ccw.

Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
---
  lib/s390x/asm/arch_def.h |   1 +
  lib/s390x/css.h          |  32 ++++++++-
  lib/s390x/css_lib.c      | 148 ++++++++++++++++++++++++++++++++++++++-
  s390x/css.c              |  94 ++++++++++++++++++++++++-
  4 files changed, 272 insertions(+), 3 deletions(-)

(...)

-int css_enable(int schid)
+/*
+ * css_enable: enable Subchannel
+ * @schid: Subchannel Identifier
+ * @isc: Interruption subclass for this subchannel as a number

"number of the interruption subclass to use"?

Yes, thanks.


+ * 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;
@@ -92,6 +103,9 @@ retry:
  	/* Update the SCHIB to enable the channel */
  	pmcw->flags |= PMCW_ENABLE;
+ /* Set Interruption Subclass to IO_SCH_ISC */

The specified isc, current callers just happen to pass that value.


Forgot to remove this comment. Will do.

+	pmcw->flags |= (isc << PMCW_ISC_SHIFT);
+
  	/* Tell the CSS we want to modify the subchannel */
  	cc = msch(schid, &schib);
  	if (cc) {
@@ -114,6 +128,7 @@ retry:
  		return cc;
  	}
+ report_info("stsch: flags: %04x", pmcw->flags);

It feels like all of this already should have been included in the
previous patch?

Yes, I did not want to modify it since it was reviewed-by.


  	if (pmcw->flags & PMCW_ENABLE) {
  		report_info("stsch: sch %08x enabled after %d retries",
  			    schid, retry_count);
@@ -129,3 +144,134 @@ retry:
  		    schid, retry_count, pmcw->flags);
  	return -1;
  }
+
+static struct irb irb;
+
+void css_irq_io(void)
+{
+	int ret = 0;
+	char *flags;
+	int sid;
+
+	report_prefix_push("Interrupt");
+	sid = lowcore_ptr->subsys_id_word;
+	/* Lowlevel set the SID as interrupt parameter. */
+	if (lowcore_ptr->io_int_param != sid) {
+		report(0,
+		       "io_int_param: %x differs from subsys_id_word: %x",
+		       lowcore_ptr->io_int_param, sid);
+		goto pop;
+	}
+	report_info("subsys_id_word: %08x io_int_param %08x io_int_word %08x",
+			lowcore_ptr->subsys_id_word,
+			lowcore_ptr->io_int_param,
+			lowcore_ptr->io_int_word);
+	report_prefix_pop();
+
+	report_prefix_push("tsch");
+	ret = tsch(sid, &irb);
+	switch (ret) {
+	case 1:
+		dump_irb(&irb);
+		flags = dump_scsw_flags(irb.scsw.ctrl);
+		report(0,
+		       "I/O interrupt, CC 1 but tsch reporting sch %08x as not status pending: %s",

"I/O interrupt, but tsch returns CC 1 for subchannel %08x" ?

Yes better, thanks


+		       sid, flags);
+		break;
+	case 2:
+		report(0, "tsch returns unexpected CC 2");
+		break;
+	case 3:
+		report(0, "tsch reporting sch %08x as not operational", sid);
+		break;
+	case 0:
+		/* Stay humble on success */
+		break;
+	}
+pop:
+	report_prefix_pop();
+	lowcore_ptr->io_old_psw.mask &= ~PSW_MASK_WAIT;
+}
+
+int start_ccw1_chain(unsigned int sid, struct ccw1 *ccw)
+{
+	struct orb orb = {
+		.intparm = sid,
+		.ctrl = ORB_CTRL_ISIC|ORB_CTRL_FMT|ORB_LPM_DFLT,
+		.cpa = (unsigned int) (unsigned long)ccw,
+	};
+
+	return ssch(sid, &orb);
+}
+
+/*
+ * In the future, we want to implement support for CCW chains;
+ * for that, we will need to work with ccw1 pointers.
+ */
+static struct ccw1 unique_ccw;
+
+int start_single_ccw(unsigned int sid, int code, void *data, int count,
+		     unsigned char flags)
+{
+	int cc;
+	struct ccw1 *ccw = &unique_ccw;
+
+	report_prefix_push("start_subchannel");
+	/* Build the CCW chain with a single CCW */
+	ccw->code = code;
+	ccw->flags = flags; /* No flags need to be set */

s/No flags/No additional flags/

obviously :)


+	ccw->count = count;
+	ccw->data_address = (int)(unsigned long)data;
+
+	cc = start_ccw1_chain(sid, ccw);
+	if (cc) {
+		report(0, "start_ccw_chain failed ret=%d", cc);
+		report_prefix_pop();
+		return cc;
+	}
+	report_prefix_pop();
+	return 0;
+}
+
+/*
+ * css_residual_count
+ * We expect no residual count when the ORB request was successful

If we have a short block, but have suppressed the incorrect length
indication, we may have a successful request with a nonzero count.
Maybe replace this with "Return the residual count, if it is valid."?


OK


+ * The residual count is valid when the subchannel is status pending
+ * with primary status and device status only or device status and
+ * subchannel status with PCI or incorrect length.
+ * Return value:
+ * Success: the residual count
+ * Not meaningful: -1 (-1 can not be a valid count)
+ */
+int css_residual_count(unsigned int schid)
+{
+
+	if (!(irb.scsw.ctrl & (SCSW_SC_PENDING | SCSW_SC_PRIMARY)))
+		goto fail;

s/fail/invalid/ ? It's not really a failure :)

yes


+
+	if (irb.scsw.dev_stat)
+		if (irb.scsw.sch_stat & ~(SCSW_SCHS_PCI | SCSW_SCHS_IL))
+			goto fail;
+
+	return irb.scsw.count;
+
+fail:
+	report_info("sch  status %02x", irb.scsw.sch_stat);
+	report_info("dev  status %02x", irb.scsw.dev_stat);
+	report_info("ctrl status %08x", irb.scsw.ctrl);
+	report_info("count       %04x", irb.scsw.count);
+	report_info("ccw addr    %08x", irb.scsw.ccw_addr);

I don't understand why you dump this data if no valid residual count is
available. But maybe I don't understand the purpose of this function
correctly.

As debug information to facilitate the search why the function failed.
Would you prefer more accurate report_info inside the if tests?
or just return with error code?



+/*
+ * test_sense
+ * Pre-requisits:

s/Pre-requisists/Pre-requisites/

OK


+ * - We need the test device as the first recognized
+ *   device by the enumeration.
+ */
+static void test_sense(void)
+{
+	int ret;
+	int len;
+
+	if (!test_device_sid) {
+		report_skip("No device");
+		return;
+	}
+
+	ret = css_enable(test_device_sid, IO_SCH_ISC);
+	if (ret) {
+		report(0,
+		       "Could not enable the subchannel: %08x",
+		       test_device_sid);
+		return;
+	}
+
+	ret = register_io_int_func(css_irq_io);
+	if (ret) {
+		report(0, "Could not register IRQ handler");
+		goto unreg_cb;
+	}
+
+	lowcore_ptr->io_int_param = 0;
+
+	memset(&senseid, 0, sizeof(senseid));
+	ret = start_single_ccw(test_device_sid, CCW_CMD_SENSE_ID,
+			       &senseid, sizeof(senseid), CCW_F_SLI);
+	if (ret) {
+		report(0, "ssch failed for SENSE ID on sch %08x with cc %d",
+		       test_device_sid, ret);
+		goto unreg_cb;
+	}
+
+	wait_for_interrupt(PSW_MASK_IO);
+
+	if (lowcore_ptr->io_int_param != test_device_sid) {
+		report(0, "ssch succeeded but interrupt parameter is wrong: expect %08x got %08x",
+		       test_device_sid, lowcore_ptr->io_int_param);
+		goto unreg_cb;
+	}
+
+	ret = css_residual_count(test_device_sid);
+	if (ret < 0) {
+		report(0, "ssch succeeded for SENSE ID but can not get a valid residual count");
+		goto unreg_cb;
+	}

I'm not sure what you're testing here. You should first test whether
the I/O concluded normally (i.e., whether you actually get something
like status pending with channel end/device end). If not, it does not
make much sense to look either at the residual count or at the sense id
data.

If css_residual_count does not return something >= 0 for that 'normal'
case, something is definitely fishy, though :)

I will add the test before the call to get the residual count.
May be it leads to rework the css_residual_count too.


+
+	len = sizeof(senseid) - ret;
+	if (ret && len < CSS_SENSEID_COMMON_LEN) {
+		report(0,
+		       "ssch succeeded for SENSE ID but report a too short length: %d",

s/report/transferred/ ?

OK


+		       ret);
+		goto unreg_cb;
+	}
+
+	if (ret && len)
+		report_info("ssch succeeded for SENSE ID but report a shorter length: %d",

Same here.

OK

snip...


Thanks for review.

Regards,
Pierre

--
Pierre Morel
IBM Lab Boeblingen



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