From 429edbe41929b626fb2742431cb2e1837e579d94 Mon Sep 17 00:00:00 2001
From: Nikita Ioffe <ioffe@google.com>
Date: Wed, 15 Feb 2023 12:45:43 +0000
Subject: [PATCH] ANDROID: KVM: arm64: Add trace_clock for nVHE tracing

Added userspace file that describes what clock is used for hyp tracing.
Unlike tracefs root instance, the hyp tracing only supports boot clock,
hence the trace_clock file is read-only.

Bug: 249050813
Change-Id: Ib9cc1f582699245ed94cf745dae0888eb7556ced
Signed-off-by: Nikita Ioffe <ioffe@google.com>
---
 arch/arm64/kvm/hyp_trace.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/arch/arm64/kvm/hyp_trace.c b/arch/arm64/kvm/hyp_trace.c
index 888a3d360f69..212e21c556b7 100644
--- a/arch/arm64/kvm/hyp_trace.c
+++ b/arch/arm64/kvm/hyp_trace.c
@@ -988,6 +988,24 @@ static const struct file_operations hyp_trace_raw_fops = {
 	.llseek		= no_llseek,
 };
 
+static int hyp_trace_clock_show(struct seq_file *m, void *v)
+{
+	seq_printf(m, "[boot]\n");
+	return 0;
+}
+
+static int hyp_trace_clock_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, hyp_trace_clock_show, NULL);
+}
+
+static const struct file_operations hyp_trace_clock_fops = {
+	.open = hyp_trace_clock_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = single_release,
+};
+
 static void hyp_tracefs_create_cpu_file(const char *file_name,
 					int cpu,
 					umode_t mode,
@@ -1028,6 +1046,11 @@ int init_hyp_tracefs(void)
 	if (!d)
 		pr_err("Failed to create tracefs "TRACEFS_DIR"/buffer_size_kb\n");
 
+	d = tracefs_create_file("trace_clock", TRACEFS_MODE_READ, root_dir, NULL,
+				&hyp_trace_clock_fops);
+	if (!d)
+		pr_err("Failed to create tracefs "TRACEFS_DIR"/trace_clock\n");
+
 	hyp_tracefs_create_cpu_file("trace", RING_BUFFER_ALL_CPUS,
 				    TRACEFS_MODE_WRITE, &hyp_trace_fops,
 				    root_dir);