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

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Date:   Fri, 13 Aug 2021 19:25:01 +1000
From:   Gavin Shan <gshan@...hat.com>
To:     Anshuman Khandual <anshuman.khandual@....com>, linux-mm@...ck.org,
        Vineet Gupta <vgupta@...nel.org>
Cc:     linux-kernel@...r.kernel.org, gerald.schaefer@...ux.ibm.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

Hi Anshuman and Vineet,

On 8/12/21 9:11 PM, Anshuman Khandual wrote:
> On 8/9/21 2:56 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 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
>>
>> Changelog
>> =========
>> v6:
>>     * Populate saved page table entry pointers after
>>       they're allocated in init_args()                        (Anshuman)
>>     * Fix imbalanced preemption count issue by replacing
>>       pte_alloc_mmap() with pte_alloc() in init_args()        (syzbot)
> 
> + vgupta@...nel.org
> 
> Hello Gavin/Vineet,
> 
> This series still need to be tested on ARC ?
> 

Yes, I'm unable to test ARC as it's not supported by QEMU yet.
It would great if Vineet can give it a try on ARC :)

Thanks,
Gavin