[PATCH v4 00/13] mm/debug_vm_pgtable fixes

[Anshuman Khandual]

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

+ linux-riscv <linux-riscv at lists.infradead.org>
+ linux-snps-arc at lists.infradead.org <linux-snps-arc at lists.infradead.org>
+ linux-s390 at vger.kernel.org
+ Gerald Schaefer <gerald.schaefer at de.ibm.com>
+ Vineet Gupta <vgupta at synopsys.com>

There is still an open git bisect issue on arm64 platform which ideally should be fixed.

- Anshuman