linux-kernel - Re: [PATCH v2 00/12] mm/debug_vm

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Date:   Mon, 19 Jul 2021 21:34:05 +1000
From:   Gavin Shan <gshan@...hat.com>
To:     linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org, anshuman.khandual@....com,
        catalin.marinas@....com, will@...nel.org,
        akpm@...ux-foundation.org, chuhu@...hat.com, shan.gavin@...il.com
Subject: Re: [PATCH v2 00/12] mm/debug_vm_pgtable: Enhancements

Hi Anshuman,

On 7/19/21 3:41 PM, Gavin Shan wrote:
> There are couple of issues with current implementations and this series
> tries to resolve the issues:
> 
>    (a) All needed information are scattered in variables, passed to various
>        test functions. The code is organized in pretty much relaxed fashion.
> 
>    (b) The page isn't allocated from buddy during page table entry modifying
>        tests. The page can be invalid, conflicting to the implementations
>        of set_xxx_at() on ARM64. The target page is accessed so that the iCache
>        can be flushed when execution permission is given on ARM64. Besides,
>        the target page can be unmapped and access to it causes kernel crash.
> 
> "struct pgtable_debug_args" is introduced to address issue (a). For issue
> (b), the used page is allocated from buddy in page table entry modifying
> tests. The corresponding tets will be skipped if we fail to allocate the
> (huge) page. For other test cases, the original page around to kernel
> symbol (@start_kernel) is still used.
> 
> The patches are organized as below. PATCH[2-10] could be combined to one
> patch, but it will make the review harder:
> 
>    PATCH[1] introduces "struct pgtable_debug_args" as place holder of all
>             needed information. With it, the old and new implementation
>             can coexist.
>    PATCH[2-10] uses "struct pgtable_debug_args" in various test functions.
>    PATCH[11] removes the old implementation.
>    PATCH[12] fixes the issue of corrupted page flag for ARM64
> 
> Changelog
> =========
> v2:
>     * Rename struct vm_pgtable_debug to struct pgtable_debug_args.
>       The parameter name to various test functions are renamed
>       to "@args"                                                  (Anshuman)
>     * Code changes as suggested by Anshuman                       (Anshuman)
> 

Please ignore v2. I will post v3 to fix couple of issues in v2:

(1) The subjects of PATCH[5/12] and PATCH[9/12] should be fixed to
     start with "mm/debug_vm_pgtable".
(2) "WARN_ON(!pud_none(pud))" is missed in PATCH[9/12]. Otherwise,
     build warning for unused variable @pud is raised.
(3) Build warnings for unused variables in separate patches are
     raised, reported by 0-DAY CI Kernel Test Service.

Thanks,
Gavin

> Gavin Shan (12):
>    mm/debug_vm_pgtable: Introduce struct pgtable_debug_args
>    mm/debug_vm_pgtable: Use struct pgtable_debug_args in basic tests
>    mm/debug_vm_pgtable: Use struct pgtable_debug_args in leaf and
>      savewrite tests
>    mm/debug_vm_pgtable: Use struct pgtable_debug_args in protnone and
>      devmap tests
>    mm/vm_debug_pgtable: Use struct pgtable_debug_args in soft_dirty and
>      swap tests
>    mm/debug_vm_pgtable: Use struct pgtable_debug_args in migration and
>      thp tests
>    mm/debug_vm_pgtable: Use struct pgtable_debug_args in PTE modifying
>      tests
>    mm/debug_vm_pgtable: Use struct pgtable_debug_args in PMD
>    mm/vm_debug_pgtable: Use struct pgtable_debug_args in PUD modifying
>      tests
>    mm/debug_vm_pgtable: Use struct pgtable_debug_args in PGD and P4D
>      modifying tests
>    mm/debug_vm_pgtable: Remove unused code
>    mm/debug_vm_pgtable: Fix corrupted page flag
> 
>   mm/debug_vm_pgtable.c | 849 ++++++++++++++++++++++++------------------
>   1 file changed, 479 insertions(+), 370 deletions(-)
>