From: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx>
Subject: mm/debug_vm_pgtable: fix kernel crash by checking for THP support
Architectures can have CONFIG_TRANSPARENT_HUGEPAGE enabled but no THP
support enabled based on platforms. For ex: with 4K PAGE_SIZE ppc64
supports THP only with radix translation.
This results in below crash when running with hash translation and 4K
PAGE_SIZE.
kernel BUG at arch/powerpc/include/asm/book3s/64/hash-4k.h:140!
cpu 0x61: Vector: 700 (Program Check) at [c000000ff948f860]
pc: c0000000018810f8: debug_vm_pgtable+0x480/0x8b0
lr: c0000000018810ec: debug_vm_pgtable+0x474/0x8b0
...
[c000000ff948faf0] c000000001880fec debug_vm_pgtable+0x374/0x8b0 (unreliable)
[c000000ff948fbf0] c000000000011648 do_one_initcall+0x98/0x4f0
[c000000ff948fcd0] c000000001843928 kernel_init_freeable+0x330/0x3fc
[c000000ff948fdb0] c0000000000122ac kernel_init+0x24/0x148
[c000000ff948fe20] c00000000000cc44 ret_from_kernel_thread+0x5c/0x78
Check for THP support correctly
Link: http://lkml.kernel.org/r/20200608125252.407659-1-aneesh.kumar@xxxxxxxxxxxxx
Fixes: 399145f9eb6c ("mm/debug: add tests validating architecture page table helpers")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
Reviewed-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/debug_vm_pgtable.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/mm/debug_vm_pgtable.c~mm-debug_vm_pgtable-fix-kernel-crash-by-checking-for-thp-support
+++ a/mm/debug_vm_pgtable.c
@@ -60,6 +60,9 @@ static void __init pmd_basic_tests(unsig
{
pmd_t pmd = pfn_pmd(pfn, prot);
+ if (!has_transparent_hugepage())
+ return;
+
WARN_ON(!pmd_same(pmd, pmd));
WARN_ON(!pmd_young(pmd_mkyoung(pmd_mkold(pmd))));
WARN_ON(!pmd_dirty(pmd_mkdirty(pmd_mkclean(pmd))));
@@ -79,6 +82,9 @@ static void __init pud_basic_tests(unsig
{
pud_t pud = pfn_pud(pfn, prot);
+ if (!has_transparent_hugepage())
+ return;
+
WARN_ON(!pud_same(pud, pud));
WARN_ON(!pud_young(pud_mkyoung(pud_mkold(pud))));
WARN_ON(!pud_write(pud_mkwrite(pud_wrprotect(pud))));
_
