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

[Aravinda Prasad]

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 <aravi...@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 */