Subject: [PATCH v5] powerpc/pseries: read the lpar name from the firmware

From: Laurent Dufour <[email-masked]>
Date: Thu, 6 Jan 2022 17:13:39 +0100

The LPAR name may be changed after the LPAR has been started in the HMC.
In that case lparstat command is not reporting the updated value because it
reads it from the device tree which is read at boot time.

However this value could be read from RTAS.

Adding this value in the /proc/powerpc/lparcfg output allows to read the
updated value.

However the hypervisor, like Qemu/KVM, may not support this RTAS
parameter. In that case the value reported in lparcfg is read from the
device tree and so is not updated accordingly.

Cc: Nathan Lynch <[email-masked]>
Signed-off-by: Laurent Dufour <[email-masked]>
---
v5:
 fallback to the device tree value if RTAS is not providing the value.
v4:
 address Nathan's new comments limiting size of the buffer.
v3:
 address Michael's comments.
v2:
 address Nathan's comments.
 change title to partition_name aligning with existing partition_id
---
 arch/powerpc/platforms/pseries/lparcfg.c | 93 ++++++++++++++++++++++++
 1 file changed, 93 insertions(+)

diff --git a/arch/powerpc/platforms/pseries/lparcfg.c b/arch/powerpc/platforms/pseries/lparcfg.c
index c7940fcfc911..8ca08fc306e7 100644
--- a/arch/powerpc/platforms/pseries/lparcfg.c
+++ b/arch/powerpc/platforms/pseries/lparcfg.c
@@ -311,6 +311,98 @@ static void parse_mpp_x_data(struct seq_file *m)
 		seq_printf(m, "coalesce_pool_spurr=%ld\n", mpp_x_data.pool_spurr_cycles);
 }
 
+/*
+ * PAPR defines, in section "7.3.16 System Parameters Option", the token 55 to
+ * read the LPAR name, and the largest output data to 4000 + 2 bytes length.
+ */
+#define SPLPAR_LPAR_NAME_TOKEN	55
+#define GET_SYS_PARM_BUF_SIZE	4002
+#if GET_SYS_PARM_BUF_SIZE > RTAS_DATA_BUF_SIZE
+#error "GET_SYS_PARM_BUF_SIZE is larger than RTAS_DATA_BUF_SIZE"
+#endif
+
+/**
+ * Read the lpar name using the RTAS ibm,get-system-parameter call.
+ *
+ * The name read through this call is updated if changes are made by the end
+ * user on the hypervisor side.
+ *
+ * Some hypervisor (like Qemu) may not provide this value. In that case, a non
+ * null value is returned.
+ */
+static int read_RTAS_lpar_name(struct seq_file *m)
+{
+	int rc, len, token;
+	union {
+		char raw_buffer[GET_SYS_PARM_BUF_SIZE];
+		struct {
+			__be16 len;
+			char name[GET_SYS_PARM_BUF_SIZE-2];
+		};
+	} *local_buffer;
+
+	token = rtas_token("ibm,get-system-parameter");
+	if (token == RTAS_UNKNOWN_SERVICE)
+		return -EINVAL;
+
+	local_buffer = kmalloc(sizeof(*local_buffer), GFP_KERNEL);
+	if (!local_buffer)
+		return -ENOMEM;
+
+	do {
+		spin_lock(&rtas_data_buf_lock);
+		memset(rtas_data_buf, 0, sizeof(*local_buffer));
+		rc = rtas_call(token, 3, 1, NULL, SPLPAR_LPAR_NAME_TOKEN,
+			       __pa(rtas_data_buf), sizeof(*local_buffer));
+		if (!rc)
+			memcpy(local_buffer->raw_buffer, rtas_data_buf,
+			       sizeof(local_buffer->raw_buffer));
+		spin_unlock(&rtas_data_buf_lock);
+	} while (rtas_busy_delay(rc));
+
+	if (!rc) {
+		/* Force end of string */
+		len = min((int) be16_to_cpu(local_buffer->len),
+			  (int) sizeof(local_buffer->name)-1);
+		local_buffer->name[len] = '\0';
+
+		seq_printf(m, "partition_name=%s\n", local_buffer->name);
+	} else
+		rc = -ENODATA;
+
+	kfree(local_buffer);
+	return rc;
+}
+
+/**
+ * Read the LPAR name from the Device Tree.
+ *
+ * The value read in the DT is not updated if the end-user is touching the LPAR
+ * name on the hypervisor side.
+ */
+static int read_DT_lpar_name(struct seq_file *m)
+{
+	struct device_node *rootdn;
+	const char *name;
+
+	rootdn = of_find_node_by_path("/");
+	if (!rootdn)
+		return -ENOENT;
+
+	name = of_get_property(rootdn, "ibm,partition-name", NULL);
+	if (!name)
+		return -ENOENT;
+
+	seq_printf(m, "partition_name=%s\n", name);
+	return 0;
+}
+
+static void read_lpar_name(struct seq_file *m)
+{
+	if (read_RTAS_lpar_name(m) && read_DT_lpar_name(m))
+		pr_err_once("Error can't get the LPAR name");
+}
+
 #define SPLPAR_CHARACTERISTICS_TOKEN 20
 #define SPLPAR_MAXLENGTH 1026*(sizeof(char))
 
@@ -496,6 +588,7 @@ static int pseries_lparcfg_data(struct seq_file *m, void *v)
 
 	if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
 		/* this call handles the ibm,get-system-parameter contents */
+		read_lpar_name(m);
 		parse_system_parameter_string(m);
 		parse_ppp_data(m);
 		parse_mpp_data(m);
-- 
2.34.1