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/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index 40847a9..09dffe6 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -871,6 +871,18 @@
}
#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 @@
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 *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 @@
/* 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);
}