Re: [kvm-unit-tests PATCH v7 09/12] s390x: css: msch, enable test

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On 2020-05-27 11:42, Cornelia Huck wrote:
On Mon, 18 May 2020 18:07:28 +0200
Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote:

A second step when testing the channel subsystem is to prepare a channel
for use.
This includes:
- Get the current subchannel Information Block (SCHIB) using STSCH
- Update it in memory to set the ENABLE bit
- Tell the CSS that the SCHIB has been modified using MSCH
- Get the SCHIB from the CSS again to verify that the subchannel is
   enabled.
- If the subchannel is not enabled retry a predefined retries count.

This tests the MSCH instruction to enable a channel succesfuly.
This is NOT a routine to really enable the channel, no retry is done,
in case of error, a report is made.

Hm... so you retry if the subchannel is not enabled after cc 0, but you
don't retry if the cc indicates busy/status pending? Makes sense, as we
don't expect the subchannel to be busy, but a more precise note in the
patch description would be good :)

OK, I add something like
"
- If the command succeed but subchannel is not enabled retry a
  predefined retries count.
- If the command fails, report the failure and do not retry, even
  if cc indicates a busy/status as we do not expect this.
"



Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
---
  s390x/css.c | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++++
  1 file changed, 67 insertions(+)

diff --git a/s390x/css.c b/s390x/css.c
index d7989d8..1b60a47 100644
--- a/s390x/css.c
+++ b/s390x/css.c
@@ -16,6 +16,7 @@
  #include <string.h>
  #include <interrupt.h>
  #include <asm/arch_def.h>
+#include <asm/time.h>
#include <css.h> @@ -65,11 +66,77 @@ out:
  	       scn, scn_found, dev_found);
  }
+#define MAX_ENABLE_RETRIES 5
+static void test_enable(void)
+{
+	struct pmcw *pmcw = &schib.pmcw;
+	int retry_count = 0;
+	int cc;
+
+	if (!test_device_sid) {
+		report_skip("No device");
+		return;
+	}
+
+	/* Read the SCHIB for this subchannel */
+	cc = stsch(test_device_sid, &schib);
+	if (cc) {
+		report(0, "stsch cc=%d", cc);
+		return;
+	}
+
+	if (pmcw->flags & PMCW_ENABLE) {
+		report(1, "stsch: sch %08x already enabled", test_device_sid);
+		return;
+	}
+
+retry:
+	/* Update the SCHIB to enable the channel */
+	pmcw->flags |= PMCW_ENABLE;
+
+	/* Tell the CSS we want to modify the subchannel */
+	cc = msch(test_device_sid, &schib);
+	if (cc) {
+		/*
+		 * If the subchannel is status pending or
+		 * if a function is in progress,
+		 * we consider both cases as errors.

Could also be cc 3, but that would be even more weird. Just logging the
cc seems fine, though.

+		 */
+		report(0, "msch cc=%d", cc);
+		return;
+	}
+
+	/*
+	 * Read the SCHIB again to verify the enablement
+	 */
+	cc = stsch(test_device_sid, &schib);
+	if (cc) {
+		report(0, "stsch cc=%d", cc);
+		return;
+	}
+
+	if (pmcw->flags & PMCW_ENABLE) {
+		report(1, "msch: sch %08x enabled after %d retries",
+		       test_device_sid, retry_count);
+		return;
+	}
+
+	if (retry_count++ < MAX_ENABLE_RETRIES) {
+		mdelay(10); /* the hardware was not ready, let it some time */

s/let/give/

+		goto retry;
+	}
+
+	report(0,
+	       "msch: enabling sch %08x failed after %d retries. pmcw: %x",
+	       test_device_sid, retry_count, pmcw->flags);
+}
+
  static struct {
  	const char *name;
  	void (*func)(void);
  } tests[] = {
  	{ "enumerate (stsch)", test_enumerate },
+	{ "enable (msch)", test_enable },
  	{ NULL, NULL }
  };

Otherwise,
Reviewed-by: Cornelia Huck <cohuck@xxxxxxxxxx>


Thanks a lot.
I make the corrections.

regards,
Pierre


--
Pierre Morel
IBM Lab Boeblingen



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