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SubjectRe: [PATCH] sparc64: mm: fix copy_tsb to correctly copy huge page TSBs
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From: Mike Kravetz <mike.kravetz@oracle.com>
Date: Fri, 2 Jun 2017 14:51:12 -0700

> When a TSB grows beyond its current capacity, a new TSB is allocated
> and copy_tsb is called to copy entries from the old TSB to the new.
> A hash shift based on page size is used to calculate the index of an
> entry in the TSB. copy_tsb has hard coded PAGE_SHIFT in these
> calculations. However, for huge page TSBs the value REAL_HPAGE_SHIFT
> should be used. As a result, when copy_tsb is called for a huge page
> TSB the entries are placed at the incorrect index in the newly
> allocated TSB. When doing hardware table walk, the MMU does not
> match these entries and we end up in the TSB miss handling code.
> This code will then create and write an entry to the correct index
> in the TSB. We take a performance hit for the table walk miss and
> recreation of these entries.
>
> Pass a new parameter to copy_tsb that is the page size shift to be
> used when copying the TSB.
>
> Suggested-by: Anthony Yznaga <anthony.yznaga@oracle.com>
> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>

Great find, applied and queued up for -stable.

Thanks!

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