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

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On 6/1/23 10:03, Janosch Frank wrote:
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?


yes up to 248



  }
  -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.


yes



+        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.


yes



+        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


OK



+
+    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.


Yes, I can let it here. I found it has little sense to give the length as parameter.

Retrying with extended length in sclp_read_scp_info() is what is done isn'it?

It does not change a lot to let the first used size here so I will let it here.



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




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