Patch "powerpc/mm/hugetlb: Filter out hugepage size not supported by page table layout" has been added to the 4.4-stable tree

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;a=summary

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 <[email protected]> know about it.

From: "Aneesh Kumar K.V" <[email protected]>
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" <[email protected]>

[ 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

---
 arch/powerpc/mm/hugetlbpage.c |   18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

@@ -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 [email protected] 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