powerpc/mm: Add some debug output when hash insertion fails

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>
---

diff --git a/arch/powerpc/include/asm/mmu-hash64.h b/arch/powerpc/include/asm/mmu-hash64.h
index 2102b214a87c9ab49b7540962c2faef15251f55c..0e398cfee2c82826b6abad1eb8ece6330df6b0b4 100644 (file)
--- a/arch/powerpc/include/asm/mmu-hash64.h
+++ b/arch/powerpc/include/asm/mmu-hash64.h
@@ -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);

diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index 40847a9dd6db619dc1cece6fd65851885bfd8047..09dffe6efa46aeae84d62a922215f87fe0a8ca2d 100644 (file)
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -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);
 }

diff --git a/arch/powerpc/mm/hugetlbpage-hash64.c b/arch/powerpc/mm/hugetlbpage-hash64.c
index faae9ec4cb04fbb7d911bb11dc4d57d91f2a6a9c..cc5c273086cf833e28bc89a91bb814b09c16a4e4 100644 (file)
--- a/arch/powerpc/mm/hugetlbpage-hash64.c
+++ b/arch/powerpc/mm/hugetlbpage-hash64.c
@@ -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;
                }