linux-kernel - Re: [PATCH V3 0/4] mm/debug_vm

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Date:   Mon, 29 Jun 2020 14:02:31 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Alexander Gordeev <agordeev@...ux.ibm.com>,
        Gerald Schaefer <gerald.schaefer@...ibm.com>
Cc:     linux-mm@...ck.org, christophe.leroy@....fr, ziy@...dia.com,
        Jonathan Corbet <corbet@....net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Vineet Gupta <vgupta@...opsys.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        linux-snps-arc@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        linux-riscv@...ts.infradead.org, x86@...nel.org,
        linux-doc@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Christophe Leroy <christophe.leroy@...roup.eu>
Subject: Re: [PATCH V3 0/4] mm/debug_vm_pgtable: Add some more tests



On 06/24/2020 08:10 PM, Alexander Gordeev wrote:
> On Wed, Jun 24, 2020 at 01:48:08PM +0200, Gerald Schaefer wrote:
>> On Wed, 24 Jun 2020 13:05:39 +0200
>> Alexander Gordeev <agordeev@...ux.ibm.com> wrote:
>>
>>> On Wed, Jun 24, 2020 at 08:43:10AM +0530, Anshuman Khandual wrote:
>>>
>>> [...]
>>>
>>>> Hello Gerald/Christophe/Vineet,
>>>>
>>>> It would be really great if you could give this series a quick test
>>>> on s390/ppc/arc platforms respectively. Thank you.
>>>
>>> That worked for me with the default and debug s390 configurations.
>>> Would you like to try with some particular options or combinations
>>> of the options?
>>
>> It will be enabled automatically on all archs that set
>> ARCH_HAS_DEBUG_VM_PGTABLE, which we do for s390 unconditionally.
>> Also, DEBUG_VM has to be set, which we have only in the debug config.
>> So only the s390 debug config will have it enabled, you can check
>> dmesg for "debug_vm_pgtable" to see when / where it was run, and if it
>> triggered any warnings.
> 
> Yes, that is what I did ;)
> 
> I should have been more clear. I wonder whether Anshuman has in
> mind other options which possibly makes sense to set or unset
> and check how it goes with non-standard configurations.

After enabling CONFIG_DEBUG_VM either explicitly or via DEBUG_VM, ideally
any memory config combination on s390 which can change platform page table
helpers (validated with CONFIG_DEBUG_VM) should also get tested. Recently,
there was a kernel crash on ppc64 [1] and a build failure on ppc32 [2] for
some particular configs. Hence it will be great if you could run this test
on multiple s390 configurations.

[1] 787d563b8642f35c5 ("mm/debug_vm_pgtable: fix kernel crash by checking for THP support")
[2] 9449c9cb420b249eb ("mm/debug_vm_pgtable: fix build failure with powerpc 8xx")

- Anshuman