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powerpc/mm/hash64: Fix subpage protection with 4K HPTE config

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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: fa28237cfc ("[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>
This commit is contained in:
Michael Ellerman 2016-05-06 16:47:12 +10:00
parent 8bbc9b7b00
commit aac55d7573
1 changed files with 9 additions and 1 deletions
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10
arch/powerpc/mm/hash_utils_64.c
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@ -1325,8 +1325,16 @@ int __hash_page(unsigned long ea, unsigned long msr, unsigned long trap,
#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;