powerpc/pseries/htmdump: Add htm status support to htmdump module

Support dumping status of Hardware Trace Macro (HTM) function
via debugfs interface. Under debugfs folder
"/sys/kernel/debug/powerpc/htmdump", add file "htmstatus".
The interface allows only read of this file which will present the
content of HTM status buffer from the hcall. The 16th offset of HTM
status buffer has value for the number of HTM entries in the status
buffer. Each nest htm status entry is 0x6 bytes, where as core HTM
status entry is 0x8 bytes. Calculate the number of bytes to read
based on this detail.

Signed-off-by: Athira Rajeev <[email protected]>
Tested-by: Venkat Rao Bagalkote <[email protected]>
Signed-off-by: Madhavan Srinivasan <[email protected]>
Link: https://patch.msgid.link/[email protected]

Author: Athira Rajeev

arch/powerpc/platforms/pseries/htmdump.c

@@ -12,6 +12,7 @@
 #include <asm/plpar_wrappers.h>
 
 static void *htm_buf;
+static void *htm_status_buf;
 static u32 nodeindex;
 static u32 nodalchipindex;
 static u32 coreindexonchip;
@@ -205,6 +206,53 @@ static int htmstart_get(void *data, u64 *val)
 	return 0;
 }
 
+static ssize_t htmstatus_read(struct file *filp, char __user *ubuf,
+			     size_t count, loff_t *ppos)
+{
+	void *htm_status_buf = filp->private_data;
+	long rc, ret;
+	u64 *num_entries;
+	u64 to_copy;
+	int htmstatus_flag;
+
+	/*
+	 * Invoke H_HTM call with:
+	 * - operation as htm status (H_HTM_OP_STATUS)
+	 * - last three values as addr, size and offset
+	 */
+	rc = htm_hcall_wrapper(nodeindex, nodalchipindex, coreindexonchip,
+				   htmtype, H_HTM_OP_STATUS, virt_to_phys(htm_status_buf),
+				   PAGE_SIZE, 0);
+
+	ret = htm_return_check(rc);
+	if (ret <= 0) {
+		pr_debug("H_HTM hcall failed for op: H_HTM_OP_STATUS, returning %ld\n", ret);
+		return ret;
+	}
+
+	/*
+	 * HTM status buffer, start of buffer + 0x10 gives the
+	 * number of HTM entries in the buffer. Each nest htm status
+	 * entry is 0x6 bytes where each core htm status entry is
+	 * 0x8 bytes.
+	 * So total count to copy is:
+	 * 32 bytes (for first 7 fields) + (number of HTM entries * entry size)
+	 */
+	num_entries = htm_status_buf + 0x10;
+	if (htmtype == 0x2)
+		htmstatus_flag = 0x8;
+	else
+		htmstatus_flag = 0x6;
+	to_copy = 32 + (be64_to_cpu(*num_entries) * htmstatus_flag);
+	return simple_read_from_buffer(ubuf, count, ppos, htm_status_buf, to_copy);
+}
+
+static const struct file_operations htmstatus_fops = {
+	.llseek = NULL,
+	.read	= htmstatus_read,
+	.open	= simple_open,
+};
+
 DEFINE_SIMPLE_ATTRIBUTE(htmconfigure_fops, htmconfigure_get, htmconfigure_set, "%llu\n");
 DEFINE_SIMPLE_ATTRIBUTE(htmstart_fops, htmstart_get, htmstart_set, "%llu\n");
 
@@ -235,6 +283,15 @@ static int htmdump_init_debugfs(void)
 	debugfs_create_file("htmconfigure", 0600, htmdump_debugfs_dir, NULL, &htmconfigure_fops);
 	debugfs_create_file("htmstart", 0600, htmdump_debugfs_dir, NULL, &htmstart_fops);
 
+	/* Debugfs interface file to present status of HTM */
+	htm_status_buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!htm_status_buf) {
+		pr_err("Failed to allocate htmstatus buf\n");
+		return -ENOMEM;
+	}
+
+	debugfs_create_file("htmstatus", 0400, htmdump_debugfs_dir, htm_status_buf, &htmstatus_fops);
+
 	return 0;
 }