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Subject: Re: [PATCH v4 00/12] mm/debug_vm_pgtable: Enhancements
To:     Gavin Shan <gshan@redhat.com>, linux-mm@kvack.org
Cc:     linux-kernel@vger.kernel.org, gerald.schaefer@linux.ibm.com,
        aneesh.kumar@linux.ibm.com, christophe.leroy@csgroup.eu,
        cai@lca.pw, catalin.marinas@arm.com, will@kernel.org,
        akpm@linux-foundation.org, chuhu@redhat.com, shan.gavin@gmail.com
References: <20210727061401.592616-1-gshan@redhat.com>
From:   Anshuman Khandual <anshuman.khandual@arm.com>
Message-ID: <8b969a2a-a883-3ce2-fac4-70ac2e3fd157@arm.com>
Date:   Thu, 29 Jul 2021 12:44:20 +0530
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On 7/27/21 11:43 AM, 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 unused code for old implementation.
>   PATCH[12] fixes the issue of corrupted page flag for ARM64
> 
> Changelog
> =========
> v4:
>    * Determine the page allocation method according to
>      MAX_ORDER                                                   (Anshuman)
>    * Move existing comments to init_args()                       (Anshuman)
>    * Code refactoring as suggested by Anshuman                   (Anshuman)
>    * Improved commit log and add comments for flush_dcache_page()
>      in PATCH[v4 12/12]                                          (Anshuman)
>    * Address misc comments                                       (Anshuman

This series builds ok on all supported platforms but should also be tested
on them as well i.e s390, ppc, arc and riscv. I was able to do some tests
on arm64 and x86 platforms.