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

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.

v3: Removed offline CPU check.

v2: Included offline CPU check and other review comments.

Signed-off-by: Aravinda Prasad <aravinda@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c
index 0b5081085a445b5edc5d3bae432f1eeac6a7fc2f..32d4452973e721ca68728827797ebb26567b435c 100644 (file)
--- 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"
 
@@ -1239,3 +1240,56 @@ 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)
+{
+       int cpu = (long)filp->private_data;
+       struct lppaca *lppaca = &lppaca_of(cpu);
+
+       return simple_read_from_buffer(buf, len, pos, lppaca,
+                               sizeof(struct lppaca));
+}
+
+static const struct file_operations vpa_fops = {
+       .open           = simple_open,
+       .read           = vpa_file_read,
+       .llseek         = default_llseek,
+};
+
+static int __init vpa_debugfs_init(void)
+{
+       char name[16];
+       long i;
+       static struct dentry *vpa_dir;
+
+       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 dentry *d;
+
+               sprintf(name, "cpu-%ld", i);
+
+               d = debugfs_create_file(name, 0400, vpa_dir, (void *)i,
+                                       &vpa_fops);
+               if (!d) {
+                       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 */