diff options
authorMichael Ellerman <>2016-05-06 16:47:12 +1000
committerMichael Ellerman <>2016-05-11 21:54:05 +1000
commitaac55d7573c5d46ed9a62818d5d3e69dd2060105 (patch)
parent8bbc9b7b001eaab8abf7e9e24edf1bb285c8d825 (diff)
powerpc/mm/hash64: Fix subpage protection with 4K HPTE config
With Linux page size of 64K and hardware only supporting 4K HPTE, if we use subpage protection, we always fail for the subpage 0 as shown below (using the selftest subpage_prot test): 520175565: (4520111850): Failed at 0x3fffad4b0000 (p=13,sp=0,w=0), want=fault, got=pass ! 4520890210: (4520826495): Failed at 0x3fffad5b0000 (p=29,sp=0,w=0), want=fault, got=pass ! 4521574251: (4521510536): Failed at 0x3fffad6b0000 (p=45,sp=0,w=0), want=fault, got=pass ! 4522258324: (4522194609): Failed at 0x3fffad7b0000 (p=61,sp=0,w=0), want=fault, got=pass ! This is because hash preload wrongly inserts the HPTE entry for subpage 0 without looking at the subpage protection information. Fix it by teaching should_hash_preload() not to preload if we have subpage protection configured for that range. It appears this has been broken since it was introduced in 2008. Fixes: fa28237cfcc5 ("[POWERPC] Provide a way to protect 4k subpages when using 64k pages") Signed-off-by: Aneesh Kumar K.V <> [mpe: Rework into should_hash_preload() to avoid build fails w/SLICES=n] Signed-off-by: Michael Ellerman <>
1 files changed, 9 insertions, 1 deletions
diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index fbe747ed8c2d..59268969a0bc 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -1325,8 +1325,16 @@ int __hash_page(unsigned long ea, unsigned long msr, unsigned long trap,
static bool should_hash_preload(struct mm_struct *mm, unsigned long ea)
+ int psize = get_slice_psize(mm, ea);
/* We only prefault standard pages for now */
- if (unlikely(get_slice_psize(mm, ea) != mm->context.user_psize))
+ if (unlikely(psize != mm->context.user_psize))
+ return false;
+ /*
+ * Don't prefault if subpage protection is enabled for the EA.
+ */
+ if (unlikely((psize == MMU_PAGE_4K) && subpage_protection(mm, ea)))
return false;
return true;