Commit a525108c authored Mar 21, 2017 by Aneesh Kumar K.V Committed by Michael Ellerman Mar 31, 2017

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



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>

parent 3a4c2601

arch/powerpc/mm/hugetlbpage.c

+18 −0

Original line number	Diff line number	Diff line
		@@ -753,6 +753,24 @@ static int __init add_huge_page_size(unsigned long long size)
		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 */