Re: [kvm-unit-tests PATCH v3 2/2] s390x: sclp: Implement SCLP_RC_INSUFFICIENT_SCCB_LENGTH

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On 5/30/23 14:40, Pierre Morel wrote:
If SCLP_CMDW_READ_SCP_INFO fails due to a short buffer, retry
with a greater buffer.

Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>

You've been testing using all possible cpus, haven't you?

  }
-static void sclp_read_scp_info(ReadInfo *ri, int length)
+static bool sclp_read_scp_info_extended(unsigned int command, ReadInfo *ri)
+{
+	int cc;
+
+	if (!test_facility(140)) {
+		report_abort("S390_FEAT_EXTENDED_LENGTH_SCCB missing");

That's the QEMU name for the facility, isn't it?
"extended-length-SCCB facility is missing" might be better since that's the name that the architecture specifies for that feature.

+		return false;
+	}
+	if (ri->h.length > (2 * PAGE_SIZE)) {

sizeof() would reduce the locations that we have to touch if we ever want to increase the buffer in the future.

+		report_abort("SCLP_READ_INFO expected size too big");
+		return false;
+	}
+
+	sclp_mark_busy();
+	memset(&ri->h, 0, sizeof(ri->h));
+	ri->h.length = 2 * PAGE_SIZE;

Same here

+
+	cc = sclp_service_call(command, ri);
+	if (cc) {
+		report_abort("SCLP_READ_INFO error");
+		return false;
+	}
+	if (ri->h.response_code != SCLP_RC_NORMAL_READ_COMPLETION) {
+		report_abort("SCLP_READ_INFO error %02x", ri->h.response_code);
+		return false;
+	}
+
+	return true;
+}
+
+static void sclp_read_scp_info(ReadInfo *ri)
  {
  	unsigned int commands[] = { SCLP_CMDW_READ_SCP_INFO_FORCED,
  				    SCLP_CMDW_READ_SCP_INFO };
+	int length = PAGE_SIZE;
  	int i, cc;
for (i = 0; i < ARRAY_SIZE(commands); i++) {
@@ -101,19 +133,29 @@ static void sclp_read_scp_info(ReadInfo *ri, int length)
  		ri->h.length = length;
cc = sclp_service_call(commands[i], ri);
-		if (cc)
-			break;
-		if (ri->h.response_code == SCLP_RC_NORMAL_READ_COMPLETION)
+		if (cc) {
+			report_abort("SCLP_READ_INFO error");
  			return;
-		if (ri->h.response_code != SCLP_RC_INVALID_SCLP_COMMAND)
+		}
+
+		switch (ri->h.response_code) {
+		case SCLP_RC_NORMAL_READ_COMPLETION:
+			return;
+		case SCLP_RC_INVALID_SCLP_COMMAND:
  			break;
+		case SCLP_RC_INSUFFICIENT_SCCB_LENGTH:
+			sclp_read_scp_info_extended(commands[i], ri);
+			return;
+		default:
+			report_abort("READ_SCP_INFO failed");
+			return;
+		}
  	}
-	report_abort("READ_SCP_INFO failed");
  }
void sclp_read_info(void)
  {
-	sclp_read_scp_info((void *)_read_info, SCCB_SIZE);

Why did you remove that?
You could have re-tried with the extended-length in sclp_read_scp_info(). Or you could return the rc and introduce a tiny function that tries both lengths depending on the rc.

+	sclp_read_scp_info((void *)_read_info);
  	read_info = (ReadInfo *)_read_info;
  }




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