| From | Ben Hutchings <> | Date | Sat, 13 Aug 2016 18:42:58 +0100 | Subject | [PATCH 3.2 19/94] powerpc/mm/hash64: Fix subpage protection with 4K HPTE config |
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3.2.82-rc1 review patch. If anyone has any objections, please let me know.
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From: Michael Ellerman <mpe@ellerman.id.au>
commit aac55d7573c5d46ed9a62818d5d3e69dd2060105 upstream.
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 <aneesh.kumar@linux.vnet.ibm.com> [mpe: Rework into should_hash_preload() to avoid build fails w/SLICES=n] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- arch/powerpc/mm/hash_utils_64.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
--- a/arch/powerpc/mm/hash_utils_64.c +++ b/arch/powerpc/mm/hash_utils_64.c @@ -1077,8 +1077,16 @@ EXPORT_SYMBOL_GPL(hash_page); #ifdef CONFIG_PPC_MM_SLICES 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;
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