powerpc/hv_gpci: Add sysfs file inside hv_gpci device to show affinity domain...

powerpc/hv_gpci: Add sysfs file inside hv_gpci device to show affinity domain via virtual processor information

The hcall H_GET_PERF_COUNTER_INFO with counter request value as
AFFINITY_DOMAIN_INFORMATION_BY_VIRTUAL_PROCESSOR(0XA0), can be used to get
the system affinity domain via virtual processor information. To expose
the system affinity domain via virtual processor information, patch adds
sysfs file called "affinity_domain_via_virtual_processor" to the
"/sys/devices/hv_gpci/interface/" of hv_gpci pmu driver.

The affinity_domain_via_virtual_processor sysfs file is only available for
power10 and above platforms. Add a macro called
INTERFACE_AFFINITY_DOMAIN_VIA_VP_ATTR, which points to the index of NULL
placeholder, for affinity_domain_via_virtual_processor attribute in
interface_attrs array. Also updated the value of INTERFACE_NULL_ATTR macro
in hv-gpci.c file.
Reviewed-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230729073455.7918-6-kjain@linux.ibm.com

arch/powerpc/perf/hv-gpci.c

@@ -105,17 +105,20 @@ static ssize_t cpumask_show(struct device *dev,
 /* Interface attribute array index to store system information */
 #define INTERFACE_PROCESSOR_BUS_TOPOLOGY_ATTR	6
 #define INTERFACE_PROCESSOR_CONFIG_ATTR		7
-#define INTERFACE_NULL_ATTR			8
+#define INTERFACE_AFFINITY_DOMAIN_VIA_VP_ATTR	8
+#define INTERFACE_NULL_ATTR			9
 
 /* Counter request value to retrieve system information */
 enum {
 	PROCESSOR_BUS_TOPOLOGY,
-	PROCESSOR_CONFIG
+	PROCESSOR_CONFIG,
+	AFFINITY_DOMAIN_VIA_VP, /* affinity domain via virtual processor */
 };
 
 static int sysinfo_counter_request[] = {
 	[PROCESSOR_BUS_TOPOLOGY] = 0xD0,
 	[PROCESSOR_CONFIG] = 0x90,
+	[AFFINITY_DOMAIN_VIA_VP] = 0xA0,
 };
 
 static DEFINE_PER_CPU(char, hv_gpci_reqb[HGPCI_REQ_BUFFER_SIZE]) __aligned(sizeof(uint64_t));
@@ -316,6 +319,76 @@ static ssize_t processor_config_show(struct device *dev, struct device_attribute
 	return ret;
 }
 
+static ssize_t affinity_domain_via_virtual_processor_show(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct hv_gpci_request_buffer *arg;
+	unsigned long ret;
+	size_t n = 0;
+
+	arg = (void *)get_cpu_var(hv_gpci_reqb);
+	memset(arg, 0, HGPCI_REQ_BUFFER_SIZE);
+
+	/*
+	 * Pass the counter request 0xA0 corresponds to request
+	 * type 'Affinity_domain_information_by_virutal_processor',
+	 * to retrieve the system affinity domain information.
+	 * starting_index value refers to the starting hardware
+	 * processor index.
+	 */
+	ret = systeminfo_gpci_request(sysinfo_counter_request[AFFINITY_DOMAIN_VIA_VP],
+			0, 0, buf, &n, arg);
+
+	if (!ret)
+		return n;
+
+	if (ret != H_PARAMETER)
+		goto out;
+
+	/*
+	 * ret value as 'H_PARAMETER' corresponds to 'GEN_BUF_TOO_SMALL', which
+	 * implies that buffer can't accommodate all information, and a partial buffer
+	 * returned. To handle that, we need to take subsequent requests
+	 * with next secondary index to retrieve additional (missing) data.
+	 * Below loop do subsequent hcalls with next secondary index and add it
+	 * to buffer util we get all the information.
+	 */
+	while (ret == H_PARAMETER) {
+		int returned_values = be16_to_cpu(arg->params.returned_values);
+		int elementsize = be16_to_cpu(arg->params.cv_element_size);
+		int last_element = (returned_values - 1) * elementsize;
+
+		/*
+		 * Since the starting index and secondary index type is part of the
+		 * counter_value buffer elements, use the starting index value in the
+		 * last array element as subsequent starting index, and use secondary index
+		 * value in the last array element plus 1 as subsequent secondary index.
+		 * For counter request '0xA0', starting index points to partition id
+		 * and secondary index points to corresponding virtual processor index.
+		 */
+		u32 starting_index = arg->bytes[last_element + 1] + (arg->bytes[last_element] << 8);
+		u16 secondary_index = arg->bytes[last_element + 3] +
+				(arg->bytes[last_element + 2] << 8) + 1;
+
+		memset(arg, 0, HGPCI_REQ_BUFFER_SIZE);
+
+		ret = systeminfo_gpci_request(sysinfo_counter_request[AFFINITY_DOMAIN_VIA_VP],
+				starting_index, secondary_index, buf, &n, arg);
+
+		if (!ret)
+			return n;
+
+		if (ret != H_PARAMETER)
+			goto out;
+	}
+
+	return n;
+
+out:
+	put_cpu_var(hv_gpci_reqb);
+	return ret;
+}
+
 static DEVICE_ATTR_RO(kernel_version);
 static DEVICE_ATTR_RO(cpumask);
 
@@ -342,6 +415,11 @@ static struct attribute *interface_attrs[] = {
 	 * attribute, set in init function if applicable.
 	 */
 	NULL,
+	/*
+	 * This NULL is a placeholder for the affinity_domain_via_virtual_processor
+	 * attribute, set in init function if applicable.
+	 */
+	NULL,
 	NULL,
 };
 
@@ -592,6 +670,10 @@ static struct device_attribute *sysinfo_device_attr_create(int
 			attr->attr.name = "processor_config";
 			attr->show = processor_config_show;
 		break;
+		case INTERFACE_AFFINITY_DOMAIN_VIA_VP_ATTR:
+			attr->attr.name = "affinity_domain_via_virtual_processor";
+			attr->show = affinity_domain_via_virtual_processor_show;
+		break;
 		}
 	} else
 		pr_devel("hcall failed, with error: 0x%lx\n", ret);