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sparc64: Do not insert non-valid PTEs into the TSB hash table. 

The assumption was that update_mmu_cache() (and the equivalent for PMDs) would
only be called when the PTE being installed will be accessible by the user.

This is not true for code paths originating from remove_migration_pte().

There are dire consequences for placing a non-valid PTE into the TSB.  The TLB
miss frramework assumes thatwhen a TSB entry matches we can just load it into
the TLB and return from the TLB miss trap.

So if a non-valid PTE is in there, we will deadlock taking the TLB miss over
and over, never satisfying the miss.

Just exit early from update_mmu_cache() and friends in this situation.

Based upon a report and patch from Christopher Alexander Tobias Schulze.

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2014-08-04 16:34:01 -07:00
parent 31dab719fa
commit 18f3813252
1 changed files with 8 additions and 0 deletions
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8
arch/sparc/mm/init_64.c
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@ -351,6 +351,10 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long address, pte_t *
mm = vma->vm_mm;
/* Don't insert a non-valid PTE into the TSB, we'll deadlock. */
if (!pte_accessible(mm, pte))
return;
spin_lock_irqsave(&mm->context.lock, flags);
#if defined(CONFIG_HUGETLB_PAGE) || defined(CONFIG_TRANSPARENT_HUGEPAGE)
@ -2619,6 +2623,10 @@ void update_mmu_cache_pmd(struct vm_area_struct *vma, unsigned long addr,
pte = pmd_val(entry);
/* Don't insert a non-valid PMD into the TSB, we'll deadlock. */
if (!(pte & _PAGE_VALID))
return;
/* We are fabricating 8MB pages using 4MB real hw pages. */
pte |= (addr & (1UL << REAL_HPAGE_SHIFT));