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

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Message-Id: <20211201144826.45342-1-ldufour@linux.ibm.com>
Date:   Wed,  1 Dec 2021 15:48:26 +0100
From:   Laurent Dufour <ldufour@...ux.ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org
Cc:     nathanl@...ux.ibm.com, linux-kernel@...r.kernel.org
Subject: [PATCH] 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.

Signed-off-by: Laurent Dufour <ldufour@...ux.ibm.com>
---
 arch/powerpc/platforms/pseries/lparcfg.c | 50 ++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/arch/powerpc/platforms/pseries/lparcfg.c b/arch/powerpc/platforms/pseries/lparcfg.c
index f71eac74ea92..b597b132ce32 100644
--- a/arch/powerpc/platforms/pseries/lparcfg.c
+++ b/arch/powerpc/platforms/pseries/lparcfg.c
@@ -311,6 +311,55 @@ 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 no maximum for the LPAR name, and defines that the maximum
+ * length of the get-system-parameter's output buffer is 4000 plus 2 bytes for
+ * the length. Limit LPAR's name size to 1024
+ */
+#define SPLPAR_LPAR_NAME_MAXLEN	1026
+#define SPLPAR_LPAR_NAME_TOKEN	55
+static void parse_lpar_name(struct seq_file *m)
+{
+	int call_status, len;
+	unsigned char *local_buffer;
+
+	local_buffer = kmalloc(SPLPAR_LPAR_NAME_MAXLEN, GFP_KERNEL);
+	if (!local_buffer) {
+		pr_err("%s %s kmalloc failure at line %d\n",
+		       __FILE__, __func__, __LINE__);
+		return;
+	}
+
+	spin_lock(&rtas_data_buf_lock);
+	memset(rtas_data_buf, 0, RTAS_DATA_BUF_SIZE);
+	call_status = rtas_call(rtas_token("ibm,get-system-parameter"), 3, 1,
+				NULL,
+				SPLPAR_LPAR_NAME_TOKEN,
+				__pa(rtas_data_buf),
+				RTAS_DATA_BUF_SIZE);
+	memcpy(local_buffer, rtas_data_buf, SPLPAR_LPAR_NAME_MAXLEN);
+	spin_unlock(&rtas_data_buf_lock);
+
+	if (call_status != 0) {
+		pr_err("%s %s Error calling get-system-parameter (0x%x)\n",
+		       __FILE__, __func__, call_status);
+	} else {
+		local_buffer[SPLPAR_LPAR_NAME_MAXLEN - 1] = '\0';
+		len = local_buffer[0] * 256 + local_buffer[1];
+
+		/*
+		 * Forces an empty string in the weird case fw reports no data.
+		 */
+		if (!len)
+			local_buffer[2] = '\0';
+
+		seq_printf(m, "lpar_name=%s\n", local_buffer + 2);
+	}
+
+	kfree(local_buffer);
+}
+
+
 #define SPLPAR_CHARACTERISTICS_TOKEN 20
 #define SPLPAR_MAXLENGTH 1026*(sizeof(char))
 
@@ -496,6 +545,7 @@ 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 */
+		parse_lpar_name(m);
 		parse_system_parameter_string(m);
 		parse_ppp_data(m);
 		parse_mpp_data(m);
-- 
2.34.1