Re: [PATCH V12] mm/debug: Add tests validating architecture page table helpers

Anshuman Khandual
2020-01-30T13:12:12Z

On 01/30/2020 03:50 AM, Gerald Schaefer wrote:
> On Tue, 28 Jan 2020 06:57:53 +0530
> Anshuman Khandual <anshuman.khandual@arm.com> wrote:
>
>> This adds tests which will validate architecture page table helpers and
>> other accessors in their compliance with expected generic MM semantics.
>> This will help various architectures in validating changes to existing
>> page table helpers or addition of new ones.
>>
>> This test covers basic page table entry transformations including but not
>> limited to old, young, dirty, clean, write, write protect etc at various
>> level along with populating intermediate entries with next page table page
>> and validating them.
>>
>> Test page table pages are allocated from system memory with required size
>> and alignments. The mapped pfns at page table levels are derived from a
>> real pfn representing a valid kernel text symbol. This test gets called
>> right after page_alloc_init_late().
>>
>> This gets build and run when CONFIG_DEBUG_VM_PGTABLE is selected along with
>> CONFIG_VM_DEBUG. Architectures willing to subscribe this test also need to
>> select CONFIG_ARCH_HAS_DEBUG_VM_PGTABLE which for now is limited to x86 and
>> arm64. Going forward, other architectures too can enable this after fixing
>> build or runtime problems (if any) with their page table helpers.
>>
>> Folks interested in making sure that a given platform's page table helpers
>> conform to expected generic MM semantics should enable the above config
>> which will just trigger this test during boot. Any non conformity here will
>> be reported as an warning which would need to be fixed. This test will help
>> catch any changes to the agreed upon semantics expected from generic MM and
>> enable platforms to accommodate it thereafter.
>>
>
> [...]
>
>>
>> Tested-by: Christophe Leroy <christophe.leroy@c-s.fr> #PPC32
>
> Tested-by: Gerald Schaefer <gerald.schaefer@de.ibm.com> # s390

Thanks for testing.

>
> Thanks again for this effort, and for keeping up the spirit against
> all odds and even after 12 iterations :-)
>
>>
>> diff --git a/Documentation/features/debug/debug-vm-pgtable/arch-support.txt b/Documentation/features/debug/debug-vm-pgtable/arch-support.txt
>> new file mode 100644
>> index 000000000000..f3f8111edbe3
>> --- /dev/null
>> +++ b/Documentation/features/debug/debug-vm-pgtable/arch-support.txt
>> @@ -0,0 +1,35 @@
>> +#
>> +# Feature name: debug-vm-pgtable
>> +# Kconfig: ARCH_HAS_DEBUG_VM_PGTABLE
>> +# description: arch supports pgtable tests for semantics compliance
>> +#
>> + -----------------------
>> + | arch |status|
>> + -----------------------
>> + | alpha: | TODO |
>> + | arc: | ok |
>> + | arm: | TODO |
>> + | arm64: | ok |
>> + | c6x: | TODO |
>> + | csky: | TODO |
>> + | h8300: | TODO |
>> + | hexagon: | TODO |
>> + | ia64: | TODO |
>> + | m68k: | TODO |
>> + | microblaze: | TODO |
>> + | mips: | TODO |
>> + | nds32: | TODO |
>> + | nios2: | TODO |
>> + | openrisc: | TODO |
>> + | parisc: | TODO |
>> + | powerpc/32: | ok |
>> + | powerpc/64: | TODO |
>> + | riscv: | TODO |
>> + | s390: | TODO |
>
> s390 is ok now, with my patches included in v5.5-rc1. So you can now add
>
> --- a/Documentation/features/debug/debug-vm-pgtable/arch-support.txt
> +++ b/Documentation/features/debug/debug-vm-pgtable/arch-support.txt
> @@ -25,7 +25,7 @@
> | powerpc/32: | ok |
> | powerpc/64: | TODO |
> | riscv: | TODO |
> - | s390: | TODO |
> + | s390: | ok |
> | sh: | TODO |
> | sparc: | TODO |
> | um: | TODO |
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -59,6 +59,7 @@ config KASAN_SHADOW_OFFSET
> config S390
> def_bool y
> select ARCH_BINFMT_ELF_STATE
> + select ARCH_HAS_DEBUG_VM_PGTABLE
> select ARCH_HAS_DEVMEM_IS_ALLOWED
> select ARCH_HAS_ELF_RANDOMIZE
> select ARCH_HAS_FORTIFY_SOURCE

Sure, will add this up.