[PATCH] powerpc/pseries: Export raw per-CPU VPA data via debugfs

[Aravinda Prasad <aravinda@linux.vnet.ibm.com>]

This patch exports the raw per-CPU VPA data via debugfs.
A per-CPU file is created which exports the VPA data of
that CPU to help debug some of the VPA related issues or
to analyze the per-CPU VPA related statistics.

Signed-off-by: Aravinda Prasad <aravinda@linux.vnet.ibm.com>
---
 arch/powerpc/platforms/pseries/lpar.c |   85 +++++++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)

diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c
index d3992ce..cc12c12 100644
--- a/arch/powerpc/platforms/pseries/lpar.c
+++ b/arch/powerpc/platforms/pseries/lpar.c
@@ -48,6 +48,7 @@
 #include <asm/kexec.h>
 #include <asm/fadump.h>
 #include <asm/asm-prototypes.h>
+#include <asm/debugfs.h>
 
 #include "pseries.h"
 
@@ -64,6 +65,16 @@ EXPORT_SYMBOL(plpar_hcall);
 EXPORT_SYMBOL(plpar_hcall9);
 EXPORT_SYMBOL(plpar_hcall_norets);
 
+#ifdef CONFIG_DEBUG_FS
+struct vpa {
+	struct dentry	*file;
+	int		cpu;
+};
+static DEFINE_PER_CPU(struct vpa, cpu_vpa);
+
+static struct dentry *vpa_dir;
+#endif
+
 void vpa_init(int cpu)
 {
 	int hwcpu = get_hard_smp_processor_id(cpu);
@@ -1028,3 +1039,77 @@ static int __init reserve_vrma_context_id(void)
 	return 0;
 }
 machine_device_initcall(pseries, reserve_vrma_context_id);
+
+#ifdef CONFIG_DEBUG_FS
+/* debugfs file interface for vpa data */
+static ssize_t vpa_file_read(struct file *filp, char __user *buf, size_t len,
+		loff_t *pos)
+{
+	long int rc;
+	struct vpa *vpa = filp->private_data;
+	struct lppaca *lppaca = &lppaca_of(vpa->cpu);
+
+	if (len < sizeof(struct lppaca))
+		return -EINVAL;
+
+	rc = copy_to_user(buf, lppaca, sizeof(struct lppaca));
+	if (rc)
+		return -EFAULT;
+
+	return 0;
+}
+
+static int vpa_file_open(struct inode *inode, struct file *filp)
+{
+	struct vpa *vpa = inode->i_private;
+
+	filp->private_data = vpa;
+	return 0;
+}
+
+static int vpa_file_release(struct inode *inode, struct file *filp)
+{
+	return 0;
+}
+
+static const struct file_operations vpa_fops = {
+	.open		= vpa_file_open,
+	.release	= vpa_file_release,
+	.read		= vpa_file_read,
+	.llseek		= no_llseek,
+};
+
+static int __init vpa_debugfs_init(void)
+{
+	char name[10];
+	int i;
+
+	if (!firmware_has_feature(FW_FEATURE_SPLPAR))
+		return 0;
+
+	vpa_dir = debugfs_create_dir("vpa", powerpc_debugfs_root);
+	if (!vpa_dir) {
+		pr_warn("%s: can't create vpa root dir\n", __func__);
+		return -ENOMEM;
+	}
+
+	/* set up the per-cpu vpa file*/
+	for_each_possible_cpu(i) {
+		struct vpa *vpa = &per_cpu(cpu_vpa, i);
+
+		vpa->cpu = i;
+		sprintf(name, "cpu-%d", i);
+
+		vpa->file = debugfs_create_file(name, 0400, vpa_dir, vpa,
+					&vpa_fops);
+		if (!vpa->file) {
+			pr_warn("%s: can't create per-cpu vpa file\n",
+					__func__);
+			return -ENOMEM;
+		}
+	}
+
+	return 0;
+}
+machine_arch_initcall(pseries, vpa_debugfs_init);
+#endif /* CONFIG_DEBUG_FS */