x86: Add a debugfs interface to dump PAT memtype

Add a debugfs interface to list out all the PAT memtype reservations.
Appears at debugfs x86/pat_memtype_list and output format is
type @ <start addr>-<end addr>

We do not hold the lock while printing the entire list. So, the list may not be
a consistent copy in case where regions are getting added or deleted
at the same time.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 88 insertions, 0 deletions

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index d4585077977a..0917a540a55e 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -12,6 +12,8 @@
 #include <linux/gfp.h>
 #include <linux/fs.h>
 #include <linux/bootmem.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
 
 #include <asm/msr.h>
 #include <asm/tlbflush.h>
@@ -489,3 +491,89 @@ void unmap_devmem(unsigned long pfn, unsigned long size, pgprot_t vma_prot)
 
         free_memtype(addr, addr + size);
 }
+
+#if defined(CONFIG_DEBUG_FS)
+
+/* get Nth element of the linked list */
+static struct memtype *memtype_get_idx(loff_t pos)
+{
+        struct memtype *list_node, *print_entry;
+        int i = 1;
+
+        print_entry  = kmalloc(sizeof(struct memtype), GFP_KERNEL);
+        if (!print_entry)
+                return NULL;
+
+        spin_lock(&memtype_lock);
+        list_for_each_entry(list_node, &memtype_list, nd) {
+                if (pos == i) {
+                        *print_entry = *list_node;
+                        spin_unlock(&memtype_lock);
+                        return print_entry;
+                }
+                ++i;
+        }
+        spin_unlock(&memtype_lock);
+        kfree(print_entry);
+        return NULL;
+}
+
+static void *memtype_seq_start(struct seq_file *seq, loff_t *pos)
+{
+        if (*pos == 0) {
+                ++*pos;
+                seq_printf(seq, "PAT memtype list:\n");
+        }
+
+        return memtype_get_idx(*pos);
+}
+
+static void *memtype_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+        ++*pos;
+        return memtype_get_idx(*pos);
+}
+
+static void memtype_seq_stop(struct seq_file *seq, void *v)
+{
+}
+
+static int memtype_seq_show(struct seq_file *seq, void *v)
+{
+        struct memtype *print_entry = (struct memtype *)v;
+
+        seq_printf(seq, "%s @ 0x%Lx-0x%Lx\n", cattr_name(print_entry->type),
+                        print_entry->start, print_entry->end);
+        kfree(print_entry);
+        return 0;
+}
+
+static struct seq_operations memtype_seq_ops = {
+        .start = memtype_seq_start,
+        .next  = memtype_seq_next,
+        .stop  = memtype_seq_stop,
+        .show  = memtype_seq_show,
+};
+
+static int memtype_seq_open(struct inode *inode, struct file *file)
+{
+        return seq_open(file, &memtype_seq_ops);
+}
+
+static const struct file_operations memtype_fops = {
+        .open    = memtype_seq_open,
+        .read    = seq_read,
+        .llseek  = seq_lseek,
+        .release = seq_release,
+};
+
+static int __init pat_memtype_list_init(void)
+{
+        debugfs_create_file("pat_memtype_list", S_IRUSR, arch_debugfs_dir,
+                                NULL, &memtype_fops);
+        return 0;
+}
+
+late_initcall(pat_memtype_list_init);
+
+#endif /* CONFIG_DEBUG_FS */