powerpc/mm: Add some debug output when hash insertion fails
authorBenjamin Herrenschmidt <benh@kernel.crashing.org>
Fri, 23 Jul 2010 00:31:13 +0000 (10:31 +1000)
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>
Fri, 23 Jul 2010 02:56:56 +0000 (12:56 +1000)
This adds some debug output to our MMU hash code to print out some
useful debug data if the hypervisor refuses the insertion (which
should normally never happen).

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---

arch/powerpc/include/asm/mmu-hash64.h
arch/powerpc/mm/hash_utils_64.c
arch/powerpc/mm/hugetlbpage-hash64.c

index 2102b21..0e398cf 100644 (file)
@@ -250,7 +250,9 @@ extern int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
 int __hash_page_huge(unsigned long ea, unsigned long access, unsigned long vsid,
                     pte_t *ptep, unsigned long trap, int local, int ssize,
                     unsigned int shift, unsigned int mmu_psize);
-
+extern void hash_failure_debug(unsigned long ea, unsigned long access,
+                              unsigned long vsid, unsigned long trap,
+                              int ssize, int psize, unsigned long pte);
 extern int htab_bolt_mapping(unsigned long vstart, unsigned long vend,
                             unsigned long pstart, unsigned long prot,
                             int psize, int ssize);
index 40847a9..09dffe6 100644 (file)
@@ -871,6 +871,18 @@ static inline int subpage_protection(struct mm_struct *mm, unsigned long ea)
 }
 #endif
 
+void hash_failure_debug(unsigned long ea, unsigned long access,
+                       unsigned long vsid, unsigned long trap,
+                       int ssize, int psize, unsigned long pte)
+{
+       if (!printk_ratelimit())
+               return;
+       pr_info("mm: Hashing failure ! EA=0x%lx access=0x%lx current=%s\n",
+               ea, access, current->comm);
+       pr_info("    trap=0x%lx vsid=0x%lx ssize=%d psize=%d pte=0x%lx\n",
+               trap, vsid, ssize, psize, pte);
+}
+
 /* Result code is:
  *  0 - handled
  *  1 - normal page fault
@@ -1036,6 +1048,12 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
                                            local, ssize, spp);
        }
 
+       /* Dump some info in case of hash insertion failure, they should
+        * never happen so it is really useful to know if/when they do
+        */
+       if (rc == -1)
+               hash_failure_debug(ea, access, vsid, trap, ssize, psize,
+                                  pte_val(*ptep));
 #ifndef CONFIG_PPC_64K_PAGES
        DBG_LOW(" o-pte: %016lx\n", pte_val(*ptep));
 #else
@@ -1054,8 +1072,7 @@ void hash_preload(struct mm_struct *mm, unsigned long ea,
        void *pgdir;
        pte_t *ptep;
        unsigned long flags;
-       int local = 0;
-       int ssize;
+       int rc, ssize, local = 0;
 
        BUG_ON(REGION_ID(ea) != USER_REGION_ID);
 
@@ -1101,11 +1118,18 @@ void hash_preload(struct mm_struct *mm, unsigned long ea,
        /* Hash it in */
 #ifdef CONFIG_PPC_HAS_HASH_64K
        if (mm->context.user_psize == MMU_PAGE_64K)
-               __hash_page_64K(ea, access, vsid, ptep, trap, local, ssize);
+               rc = __hash_page_64K(ea, access, vsid, ptep, trap, local, ssize);
        else
 #endif /* CONFIG_PPC_HAS_HASH_64K */
-               __hash_page_4K(ea, access, vsid, ptep, trap, local, ssize,
-                              subpage_protection(pgdir, ea));
+               rc = __hash_page_4K(ea, access, vsid, ptep, trap, local, ssize,
+                                   subpage_protection(pgdir, ea));
+
+       /* Dump some info in case of hash insertion failure, they should
+        * never happen so it is really useful to know if/when they do
+        */
+       if (rc == -1)
+               hash_failure_debug(ea, access, vsid, trap, ssize,
+                                  mm->context.user_psize, pte_val(*ptep));
 
        local_irq_restore(flags);
 }
index faae9ec..cc5c273 100644 (file)
@@ -127,6 +127,8 @@ repeat:
                 */
                if (unlikely(slot == -2)) {
                        *ptep = __pte(old_pte);
+                       hash_failure_debug(ea, access, vsid, trap, ssize,
+                                          mmu_psize, old_pte);
                        return -1;
                }