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    Subject[PATCH 4.9 086/241] powerpc/mm/hugetlb: Filter out hugepage size not supported by page table layout
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>


    [ Upstream commit a525108cf1cc14651602d678da38fa627a76a724 ]

    Without this if firmware reports 1MB page size support we will crash
    trying to use 1MB as hugetlb page size.

    echo 300 > /sys/kernel/mm/hugepages/hugepages-1024kB/nr_hugepages

    kernel BUG at ./arch/powerpc/include/asm/hugetlb.h:19!
    .....
    ....
    [c0000000e2c27b30] c00000000029dae8 .hugetlb_fault+0x638/0xda0
    [c0000000e2c27c30] c00000000026fb64 .handle_mm_fault+0x844/0x1d70
    [c0000000e2c27d70] c00000000004805c .do_page_fault+0x3dc/0x7c0
    [c0000000e2c27e30] c00000000000ac98 handle_page_fault+0x10/0x30

    With fix, we don't enable 1MB as hugepage size.

    bash-4.2# cd /sys/kernel/mm/hugepages/
    bash-4.2# ls
    hugepages-16384kB hugepages-16777216kB

    Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/powerpc/mm/hugetlbpage.c | 18 ++++++++++++++++++
    1 file changed, 18 insertions(+)

    --- a/arch/powerpc/mm/hugetlbpage.c
    +++ b/arch/powerpc/mm/hugetlbpage.c
    @@ -765,6 +765,24 @@ static int __init add_huge_page_size(uns
    if ((mmu_psize = shift_to_mmu_psize(shift)) < 0)
    return -EINVAL;

    +#ifdef CONFIG_PPC_BOOK3S_64
    + /*
    + * We need to make sure that for different page sizes reported by
    + * firmware we only add hugetlb support for page sizes that can be
    + * supported by linux page table layout.
    + * For now we have
    + * Radix: 2M
    + * Hash: 16M and 16G
    + */
    + if (radix_enabled()) {
    + if (mmu_psize != MMU_PAGE_2M)
    + return -EINVAL;
    + } else {
    + if (mmu_psize != MMU_PAGE_16M && mmu_psize != MMU_PAGE_16G)
    + return -EINVAL;
    + }
    +#endif
    +
    BUG_ON(mmu_psize_defs[mmu_psize].shift != shift);

    /* Return if huge page size has already been setup */

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