linux-kernel - [PATCH v4] powerpc/pseries: read the lpar name from the firmware

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Message-Id: <20211207171109.22793-1-ldufour@linux.ibm.com>
Date:   Tue,  7 Dec 2021 18:11:09 +0100
From:   Laurent Dufour <ldufour@...ux.ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org
Cc:     linux-kernel@...r.kernel.org, Nathan Lynch <nathanl@...ux.ibm.com>
Subject: [PATCH v4] powerpc/pseries: read the lpar name from the firmware

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.

Cc: Nathan Lynch <nathanl@...ux.ibm.com>
Signed-off-by: Laurent Dufour <ldufour@...ux.ibm.com>
---
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 | 54 ++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/arch/powerpc/platforms/pseries/lparcfg.c b/arch/powerpc/platforms/pseries/lparcfg.c
index f71eac74ea92..058d9a5fe545 100644
--- a/arch/powerpc/platforms/pseries/lparcfg.c
+++ b/arch/powerpc/platforms/pseries/lparcfg.c
@@ -311,6 +311,59 @@ 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
+static void read_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;
+
+	local_buffer = kmalloc(sizeof(*local_buffer), GFP_KERNEL);
+	if (!local_buffer)
+		return;
+
+	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
+		pr_err_once("Error calling get-system-parameter (0x%x)\n", rc);
+
+	kfree(local_buffer);
+}
+
+
 #define SPLPAR_CHARACTERISTICS_TOKEN 20
 #define SPLPAR_MAXLENGTH 1026*(sizeof(char))
 
@@ -496,6 +549,7 @@ 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