This is a note to let you know that I've just added the patch titled

powerpc/mm/hugetlb: Filter out hugepage size not supported by page table layout

to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: powerpc-mm-hugetlb-filter-out-hugepage-size-not-supported-by-page-table-layout.patch and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Mon Mar 19 09:58:12 CET 2018

From: "Aneesh Kumar K.V" aneesh.kumar@linux.vnet.ibm.com Date: Tue, 21 Mar 2017 22:59:56 +0530 Subject: powerpc/mm/hugetlb: Filter out hugepage size not supported by page table layout

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 @@ -828,6 +828,24 @@ 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 */

Patches currently in stable-queue which might be from aneesh.kumar@linux.vnet.ibm.com are

queue-4.4/mm-fix-false-positive-vm_bug_on-in-page_cache_-get-add-_speculative.patch queue-4.4/powerpc-mm-hugetlb-filter-out-hugepage-size-not-supported-by-page-table-layout.patch