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

From: Gerald Schaefer <[email-masked]>
Date: Wed, 29 Jan 2020 23:20:28 +0100

On Tue, 28 Jan 2020 06:57:53 +0530
Anshuman Khandual <[email-masked]> 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 <[email-masked]>		#PPC32

Tested-by: Gerald Schaefer <[email-masked]> # s390

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

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