On 03/27/2020 12:30 PM, Christophe Leroy wrote:

On 03/27/2020 06:46 AM, Anshuman Khandual wrote:

quoted

On 03/26/2020 08:53 PM, Christophe Leroy wrote:

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Le 26/03/2020 à 03:23, Anshuman Khandual a écrit :

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On 03/24/2020 10:52 AM, Anshuman Khandual wrote:

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This series adds more arch page table helper tests. The new tests here are
either related to core memory functions and advanced arch pgtable helpers.
This also creates a documentation file enlisting all expected semantics as
suggested by Mike Rapoport (https://lkml.org/lkml/2020/1/30/40).

This series has been tested on arm64 and x86 platforms.

If folks can test these patches out on remaining ARCH_HAS_DEBUG_VM_PGTABLE
enabled platforms i.e s390, arc, powerpc (32 and 64), that will be really
appreciated. Thank you.

On powerpc 8xx (PPC32), I get:

[   53.338368] debug_vm_pgtable: debug_vm_pgtable: Validating architecture page table helpers
[   53.347403] ------------[ cut here ]------------
[   53.351832] WARNING: CPU: 0 PID: 1 at mm/debug_vm_pgtable.c:647 debug_vm_pgtable+0x280/0x3f4

mm/debug_vm_pgtable.c:647 ?

With the following commits in place

53a8338ce (HEAD) Documentation/mm: Add descriptions for arch page table helper
5d4913fc1 mm/debug: Add tests validating arch advanced page table helpers
bcaf120a7 mm/debug: Add tests validating arch page table helpers for core features
d6ed5a4a5 x86/memory: Drop pud_mknotpresent()
0739d1f8d mm/debug: Add tests validating architecture page table helpers
16fbf79b0 (tag: v5.6-rc7) Linux 5.6-rc7

I have:

facaa5eb5909 (HEAD -> helpers0) mm/debug: Add tests validating arch advanced page table helpers
6389fed515fc mm/debug: Add tests validating arch page table helpers for core features
dc14ecc8b94e mm/debug: add tests validating architecture page table helpers
c6624071c338 (origin/merge, merge) Automatic merge of branches 'master', 'next' and 'fixes' into merge
58e05c5508e6 Automatic merge of branches 'master', 'next' and 'fixes' into merge
1b649e0bcae7 (origin/master, origin/HEAD) Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

origin is https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git

I can't see your last patch in powerpc mailing list (https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=166237)

My bad, did not update the last patch with required lists (will fix).

quoted

mm/debug_vm_pgtable.c:647 is here.

Line 647 is:

    WARN_ON(!pte_same(pte, __swp_entry_to_pte(swp)));

Both set of definitions suggest that the last three bits (if present)
on the PTE will be discarded during PTE->SWP->PTE conversion which
might be leading to this mismatch and subsequent failure.

arch/powerpc/include/asm/nohash/32/pgtable.h
arch/powerpc/include/asm/book3s/32/pgtable.h

#define __pte_to_swp_entry(pte)         ((swp_entry_t) { pte_val(pte) >> 3 })
#define __swp_entry_to_pte(x)           ((pte_t) { (x).val << 3 })

Also there are some more architectures (microblaze, sh, etc) where these
conversions are not always preserving. On powerpc64, it sets back _PAGE_PTE
irrespective of whether the bit was originally set or not.

Probably it is wrong to expect that PTE->SWP->PTE conversion will be always
preserving. So wondering if it is worth changing this test to accommodate
all such architectures or just drop it instead.

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#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
static void __init pmd_swap_tests(unsigned long pfn, pgprot_t prot)
{
         swp_entry_t swp;
         pmd_t pmd;  -----------------------------> Line #647

         pmd = pfn_pmd(pfn, prot);
         swp = __pmd_to_swp_entry(pmd);
         WARN_ON(!pmd_same(pmd, __swp_entry_to_pmd(swp)));
}
#else
static void __init pmd_swap_tests(unsigned long pfn, pgprot_t prot) { }
#end

Did I miss something ?

[...]

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Could you please point me to the exact test which is failing ?

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[   53.519778] Freeing unused kernel memory: 608K

So I assume that the system should have come till runtime just fine apart from
the above warning message because.

Yes it boots fine otherwise.

Cool, that is good to know.

Christophe