powerpc/pseries: new lparcfg key/value pair: partition_affinity_score

The H_GetPerformanceCounterInfo (GPCI) PHYP hypercall has a subcall,
Affinity_Domain_Info_By_Partition, which returns, among other things,
a "partition affinity score" for a given LPAR.  This score, a value on
[0-100], represents the processor-memory affinity for the LPAR in
question.  A score of 0 indicates the worst possible affinity while a
score of 100 indicates perfect affinity.  The score can be used to
reason about performance.

This patch adds the score for the local LPAR to the lparcfg procfile
under a new 'partition_affinity_score' key.
Signed-off-by: Scott Cheloha <cheloha@linux.ibm.com>
Reviewed-by: Tyrel Datwyler <tyreld@linux.ibm.com>
Acked-by: Nathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200727184605.2945095-2-cheloha@linux.ibm.com

arch/powerpc/platforms/pseries/lparcfg.c

@@ -136,6 +136,39 @@ static unsigned int h_get_ppp(struct hvcall_ppp_data *ppp_data)
 	return rc;
 }
 
+static void show_gpci_data(struct seq_file *m)
+{
+	struct hv_gpci_request_buffer *buf;
+	unsigned int affinity_score;
+	long ret;
+
+	buf = kmalloc(sizeof(*buf), GFP_KERNEL);
+	if (buf == NULL)
+		return;
+
+	/*
+	 * Show the local LPAR's affinity score.
+	 *
+	 * 0xB1 selects the Affinity_Domain_Info_By_Partition subcall.
+	 * The score is at byte 0xB in the output buffer.
+	 */
+	memset(&buf->params, 0, sizeof(buf->params));
+	buf->params.counter_request = cpu_to_be32(0xB1);
+	buf->params.starting_index = cpu_to_be32(-1);	/* local LPAR */
+	buf->params.counter_info_version_in = 0x5;	/* v5+ for score */
+	ret = plpar_hcall_norets(H_GET_PERF_COUNTER_INFO, virt_to_phys(buf),
+				 sizeof(*buf));
+	if (ret != H_SUCCESS) {
+		pr_debug("hcall failed: H_GET_PERF_COUNTER_INFO: %ld, %x\n",
+			 ret, be32_to_cpu(buf->params.detail_rc));
+		goto out;
+	}
+	affinity_score = buf->bytes[0xB];
+	seq_printf(m, "partition_affinity_score=%u\n", affinity_score);
+out:
+	kfree(buf);
+}
+
 static unsigned h_pic(unsigned long *pool_idle_time,
 		      unsigned long *num_procs)
 {
@@ -487,6 +520,8 @@ static int pseries_lparcfg_data(struct seq_file *m, void *v)
 			   partition_active_processors * 100);
 	}
 
+	show_gpci_data(m);
+
 	seq_printf(m, "partition_active_processors=%d\n",
 		   partition_active_processors);