linux-kernel - Re: [PATCH v6 00/12] mm/debug_vm

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Message-ID: <20210810180535.08ecc800@thinkpad>
Date:   Tue, 10 Aug 2021 18:05:35 +0200
From:   Gerald Schaefer <gerald.schaefer@...ux.ibm.com>
To:     Gavin Shan <gshan@...hat.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        anshuman.khandual@....com, aneesh.kumar@...ux.ibm.com,
        christophe.leroy@...roup.eu, cai@....pw, catalin.marinas@....com,
        will@...nel.org, vgupta@...opsys.com, akpm@...ux-foundation.org,
        chuhu@...hat.com, shan.gavin@...il.com
Subject: Re: [PATCH v6 00/12] mm/debug_vm_pgtable: Enhancements

On Mon,  9 Aug 2021 17:26:19 +0800
Gavin Shan <gshan@...hat.com> 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 accessing 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

Tested on s390, all seems to work fine.

Gerald