powerpc/mce: Don't reload pte val in addr_to_pfn

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A lockless page table walk should be safe against parallel THP collapse, THP
split and madvise(MADV_DONTNEED)/parallel fault. This patch makes sure kernel
won't reload the pteval when checking for different conditions. The patch also added
a check for pte_present to make sure the kernel is indeed operating
on a PTE and not a pointer to level 0 table page.

The pfn value we find here can be different from the actual pfn on which
machine check happened. This can happen if we raced with a parallel update
of the page table. In such a scenario we end up isolating a wrong pfn. But that
doesn't have any other side effect.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200505071729.54912-7-aneesh.kumar@linux.ibm.com

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Aneesh Kumar K.V 2020-05-05 12:47:13 +05:30 • committed by Michael Ellerman

parent 2f92447f9f

commit 0da81b658b

1 changed files with 9 additions and 5 deletions

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arch/powerpc/kernel/mce_power.c

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