On 09/04/2020 09:31 PM, Gerald Schaefer wrote: > On Fri, 4 Sep 2020 17:26:47 +0200 > Gerald Schaefer <gerald.schaefer@xxxxxxxxxxxxx> wrote: > >> On Fri, 4 Sep 2020 12:18:05 +0530 >> Anshuman Khandual <anshuman.khandual@xxxxxxx> wrote: >> >>> >>> >>> On 09/02/2020 05:12 PM, Aneesh Kumar K.V wrote: >>>> This patch series includes fixes for debug_vm_pgtable test code so that >>>> they follow page table updates rules correctly. The first two patches introduce >>>> changes w.r.t ppc64. The patches are included in this series for completeness. We can >>>> merge them via ppc64 tree if required. >>>> >>>> Hugetlb test is disabled on ppc64 because that needs larger change to satisfy >>>> page table update rules. >>>> >>>> These tests are broken w.r.t page table update rules and results in kernel >>>> crash as below. >>>> >>>> [ 21.083519] kernel BUG at arch/powerpc/mm/pgtable.c:304! >>>> cpu 0x0: Vector: 700 (Program Check) at [c000000c6d1e76c0] >>>> pc: c00000000009a5ec: assert_pte_locked+0x14c/0x380 >>>> lr: c0000000005eeeec: pte_update+0x11c/0x190 >>>> sp: c000000c6d1e7950 >>>> msr: 8000000002029033 >>>> current = 0xc000000c6d172c80 >>>> paca = 0xc000000003ba0000 irqmask: 0x03 irq_happened: 0x01 >>>> pid = 1, comm = swapper/0 >>>> kernel BUG at arch/powerpc/mm/pgtable.c:304! >>>> [link register ] c0000000005eeeec pte_update+0x11c/0x190 >>>> [c000000c6d1e7950] 0000000000000001 (unreliable) >>>> [c000000c6d1e79b0] c0000000005eee14 pte_update+0x44/0x190 >>>> [c000000c6d1e7a10] c000000001a2ca9c pte_advanced_tests+0x160/0x3d8 >>>> [c000000c6d1e7ab0] c000000001a2d4fc debug_vm_pgtable+0x7e8/0x1338 >>>> [c000000c6d1e7ba0] c0000000000116ec do_one_initcall+0xac/0x5f0 >>>> [c000000c6d1e7c80] c0000000019e4fac kernel_init_freeable+0x4dc/0x5a4 >>>> [c000000c6d1e7db0] c000000000012474 kernel_init+0x24/0x160 >>>> [c000000c6d1e7e20] c00000000000cbd0 ret_from_kernel_thread+0x5c/0x6c >>>> >>>> With DEBUG_VM disabled >>>> >>>> [ 20.530152] BUG: Kernel NULL pointer dereference on read at 0x00000000 >>>> [ 20.530183] Faulting instruction address: 0xc0000000000df330 >>>> cpu 0x33: Vector: 380 (Data SLB Access) at [c000000c6d19f700] >>>> pc: c0000000000df330: memset+0x68/0x104 >>>> lr: c00000000009f6d8: hash__pmdp_huge_get_and_clear+0xe8/0x1b0 >>>> sp: c000000c6d19f990 >>>> msr: 8000000002009033 >>>> dar: 0 >>>> current = 0xc000000c6d177480 >>>> paca = 0xc00000001ec4f400 irqmask: 0x03 irq_happened: 0x01 >>>> pid = 1, comm = swapper/0 >>>> [link register ] c00000000009f6d8 hash__pmdp_huge_get_and_clear+0xe8/0x1b0 >>>> [c000000c6d19f990] c00000000009f748 hash__pmdp_huge_get_and_clear+0x158/0x1b0 (unreliable) >>>> [c000000c6d19fa10] c0000000019ebf30 pmd_advanced_tests+0x1f0/0x378 >>>> [c000000c6d19fab0] c0000000019ed088 debug_vm_pgtable+0x79c/0x1244 >>>> [c000000c6d19fba0] c0000000000116ec do_one_initcall+0xac/0x5f0 >>>> [c000000c6d19fc80] c0000000019a4fac kernel_init_freeable+0x4dc/0x5a4 >>>> [c000000c6d19fdb0] c000000000012474 kernel_init+0x24/0x160 >>>> [c000000c6d19fe20] c00000000000cbd0 ret_from_kernel_thread+0x5c/0x6c >>>> >>>> Changes from v3: >>>> * Address review feedback >>>> * Move page table depost and withdraw patch after adding pmdlock to avoid bisect failure. >>> >>> This version >>> >>> - Builds on x86, arm64, s390, arc, powerpc and riscv (defconfig with DEBUG_VM_PGTABLE) >>> - Runs on arm64 and x86 without any regression, atleast nothing that I have noticed >>> - Will be great if this could get tested on s390, arc, riscv, ppc32 platforms as well >> >> When I quickly tested v3, it worked fine, but now it turned out to >> only work fine "sometimes", both v3 and v4. I need to look into it >> further, but so far it seems related to the hugetlb_advanced_tests(). >> >> I guess there was already some discussion on this test, but we did >> not receive all of the thread(s). Please always add at least >> linux-s390@xxxxxxxxxxxxxxx and maybe myself and Vasily Gorbik <gor@xxxxxxxxxxxxx> >> for further discussions. > > BTW, with myself I mean the new address gerald.schaefer@xxxxxxxxxxxxx. > The old gerald.schaefer@xxxxxxxxxx seems to work (again), but is not > very reliable. Sure, noted. > > BTW2, a quick test with this change (so far) made the issues on s390 > go away: > > @@ -1069,7 +1074,7 @@ static int __init debug_vm_pgtable(void) > spin_unlock(ptl); > > #ifndef CONFIG_PPC_BOOK3S_64 > - hugetlb_advanced_tests(mm, vma, ptep, pte_aligned, vaddr, prot); > + hugetlb_advanced_tests(mm, vma, (pte_t *) pmdp, pmd_aligned, vaddr, prot); > #endif > > spin_lock(&mm->page_table_lock); > > That would more match the "pte_t pointer" usage for hugetlb code, > i.e. just cast a pmd_t pointer to it. Also changed to pmd_aligned, > but I think the root cause is the pte_t pointer. Ideally, the pte_t pointer used here should be from huge_pte_alloc() not from pte_alloc_map_lock() as the case currently. > > Not entirely sure though if that would really be the correct fix. > I somehow lost whatever little track I had about what these tests > really want to check, and if that would still be valid with that > change. >
