Subject: [PATCH 2/3] powerpc/pseries: Export hardware trace macro dump via debugfs

From: Madhavan Srinivasan <[email-masked]>
Date: Thu, 20 Jun 2024 23:16:13 +0530

This patch adds debugfs interface to export Hardware Trace Macro (HTM)
function data in a LPAR. New hypervisor call "H_HTM" has been
defined to setup, configure, control and dump the HTM data.
This patch supports only dumping of HTM data in a LPAR.
New debugfs folder called "htmdump" has been added under
/sys/kernel/debug/arch path which contains files need to
pass required parameters for the H_HTM dump function. New Kconfig
option called "CONFIG_HTMDUMP" has been in platform/pseries for the same.

With patch series applied and booted, list of files in debugfs path

# pwd
/sys/kernel/debug/powerpc/htmdump
# ls
coreindexonchip  htmtype  nodalchipindex  nodeindex  trace

Signed-off-by: Madhavan Srinivasan <[email-masked]>
---
 arch/powerpc/platforms/pseries/Kconfig   |   8 ++
 arch/powerpc/platforms/pseries/Makefile  |   1 +
 arch/powerpc/platforms/pseries/htmdump.c | 130 +++++++++++++++++++++++
 3 files changed, 139 insertions(+)
 create mode 100644 arch/powerpc/platforms/pseries/htmdump.c

diff --git a/arch/powerpc/platforms/pseries/Kconfig b/arch/powerpc/platforms/pseries/Kconfig
index afc0f6a61337..46c0ea605e33 100644
--- a/arch/powerpc/platforms/pseries/Kconfig
+++ b/arch/powerpc/platforms/pseries/Kconfig
@@ -128,6 +128,14 @@ config CMM
 	  will be reused for other LPARs. The interface allows firmware to
 	  balance memory across many LPARs.
 
+config HTMDUMP
+	tristate "PHYP HTM data dumper"
+	default y
+	help
+	  Select this option, if you want to enable the kernel debugfs
+	  interface to dump the Hardware Trace Macro (HTM) function data
+	  in the LPAR.
+
 config HV_PERF_CTRS
 	bool "Hypervisor supplied PMU events (24x7 & GPCI)"
 	default y
diff --git a/arch/powerpc/platforms/pseries/Makefile b/arch/powerpc/platforms/pseries/Makefile
index 7bf506f6b8c8..3f3e3492e436 100644
--- a/arch/powerpc/platforms/pseries/Makefile
+++ b/arch/powerpc/platforms/pseries/Makefile
@@ -19,6 +19,7 @@ obj-$(CONFIG_HVC_CONSOLE)	+= hvconsole.o
 obj-$(CONFIG_HVCS)		+= hvcserver.o
 obj-$(CONFIG_HCALL_STATS)	+= hvCall_inst.o
 obj-$(CONFIG_CMM)		+= cmm.o
+obj-$(CONFIG_HTMDUMP)		+= htmdump.o
 obj-$(CONFIG_IO_EVENT_IRQ)	+= io_event_irq.o
 obj-$(CONFIG_LPARCFG)		+= lparcfg.o
 obj-$(CONFIG_IBMVIO)		+= vio.o
diff --git a/arch/powerpc/platforms/pseries/htmdump.c b/arch/powerpc/platforms/pseries/htmdump.c
new file mode 100644
index 000000000000..540cdb7e069c
--- /dev/null
+++ b/arch/powerpc/platforms/pseries/htmdump.c
@@ -0,0 +1,130 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) IBM Corporation, 2024
+ */
+
+#define pr_fmt(fmt) "htmdump: " fmt
+
+#include <linux/bitops.h>
+#include <linux/string.h>
+#include <linux/init.h>
+#include <linux/moduleparam.h>
+#include <linux/fs.h>
+#include <linux/debugfs.h>
+#include <linux/slab.h>
+#include <linux/memory.h>
+#include <linux/memory_hotplug.h>
+#include <linux/numa.h>
+#include <linux/memblock.h>
+#include <asm/machdep.h>
+#include <asm/plpar_wrappers.h>
+
+/* This enables us to keep track of the memory removed from each node. */
+struct htmdump_entry {
+	void *buf;
+	struct dentry *dir;
+	char name[16];
+};
+
+static u32 nodeindex = 0;
+static u32 nodalchipindex = 0;
+static u32 coreindexonchip = 0;
+static u32 htmtype = 0;
+
+#define BUFFER_SIZE PAGE_SIZE
+
+static ssize_t htmdump_read(struct file *filp, char __user *ubuf,
+			     size_t count, loff_t *ppos)
+{
+	struct htmdump_entry *ent = filp->private_data;
+	unsigned long page, read_size, available;
+	loff_t offset;
+	long rc;
+
+	page = ALIGN_DOWN(*ppos, BUFFER_SIZE);
+	offset = (*ppos) % BUFFER_SIZE;
+
+	rc = htm_get_dump_hardware(nodeindex, nodalchipindex, coreindexonchip,
+				   htmtype, virt_to_phys(ent->buf), BUFFER_SIZE, page);
+
+	switch(rc) {
+	case H_SUCCESS:
+	case H_PARTIAL:
+		break;
+	case H_NOT_AVAILABLE:
+		return 0;
+	case H_BUSY:
+	case H_LONG_BUSY_ORDER_1_MSEC:
+	case H_LONG_BUSY_ORDER_10_MSEC:
+	case H_LONG_BUSY_ORDER_100_MSEC:
+	case H_LONG_BUSY_ORDER_1_SEC:
+	case H_LONG_BUSY_ORDER_10_SEC:
+	case H_LONG_BUSY_ORDER_100_SEC:
+	case H_PARAMETER:
+	case H_P2:
+	case H_P3:
+	case H_P4:
+	case H_P5:
+	case H_P6:
+	case H_STATE:
+	case H_AUTHORITY:
+		return -EINVAL;
+	}
+
+	available = BUFFER_SIZE - offset;
+	read_size = min(count, available);
+	*ppos += read_size;
+	return simple_read_from_buffer(ubuf, count, &offset, ent->buf, available);
+}
+
+static const struct file_operations htmdump_fops = {
+	.llseek = default_llseek,
+	.read	= htmdump_read,
+	.open	= simple_open,
+};
+
+static struct dentry *htmdump_debugfs_dir;
+
+static int htmdump_init_debugfs(void)
+{
+	struct htmdump_entry *ent;
+
+	ent = kcalloc(1, sizeof(struct htmdump_entry), GFP_KERNEL);
+	if (!ent) {
+		pr_err("Failed to allocate ent\n");
+		return -EINVAL;
+	}
+
+	ent->buf = kmalloc(BUFFER_SIZE, GFP_KERNEL);
+	if (!ent->buf) {
+		pr_err("Failed to allocate htmdump buf\n");
+		return -ENOMEM;
+	}
+
+	pr_debug("%s: ent:%lx buf:%lx\n",
+			__func__, (long unsigned int)ent, (long unsigned int)ent->buf);
+
+	htmdump_debugfs_dir = debugfs_create_dir("htmdump",
+						  arch_debugfs_dir);
+
+	debugfs_create_u32("nodeindex", 0600,
+			htmdump_debugfs_dir, &nodeindex);
+	debugfs_create_u32("nodalchipindex", 0600,
+			htmdump_debugfs_dir, &nodalchipindex);
+	debugfs_create_u32("coreindexonchip", 0600,
+			htmdump_debugfs_dir, &coreindexonchip);
+	debugfs_create_u32("htmtype", 0600,
+			htmdump_debugfs_dir, &htmtype);
+	debugfs_create_file("trace", 0400, htmdump_debugfs_dir, ent, &htmdump_fops);
+
+	return 0;
+}
+
+static int htmdump_init(void)
+{
+	if (htmdump_init_debugfs())
+		return -EINVAL;
+
+	return 0;
+}
+machine_device_initcall(pseries, htmdump_init);
-- 
2.45.2