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

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Message-ID: <25018384-acc5-dcf7-5125-378499ab4555@kernel.org>
Date:   Fri, 13 Aug 2021 12:43:55 -0700
From:   Vineet Gupta <vgupta@...nel.org>
To:     Gavin Shan <gshan@...hat.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        linux-mm@...ck.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,
        akpm@...ux-foundation.org, chuhu@...hat.com, shan.gavin@...il.com,
        arcml <linux-snps-arc@...ts.infradead.org>
Subject: Re: [PATCH v6 00/12] mm/debug_vm_pgtable: Enhancements

On 8/13/21 2:25 AM, Gavin Shan wrote:
> 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

Please also keep linux-snps-arc CC'ed for ARC changes.

>>
>> 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 :)

We do have a working QEMU (in the process of being upstreamed) you could try
https://github.com/foss-for-synopsys-dwc-arc-processors/qemu #master

Is this code in some shared git repo we can pull - instead of apply 8 files.

Thx,
-Vineet