linux-kernel - Re: [PATCH V6 0/2] mm/debug: Add tests validating architecture page table helpers

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Message-ID: <fb1fe447-d30a-21ea-1b85-0d46e14f0872@arm.com>
Date:   Wed, 16 Oct 2019 14:29:59 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Qian Cai <cai@....pw>, linux-mm@...ck.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Dan Williams <dan.j.williams@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Michal Hocko <mhocko@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Mark Brown <broonie@...nel.org>,
        Steven Price <Steven.Price@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Kees Cook <keescook@...omium.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Matthew Wilcox <willy@...radead.org>,
        Sri Krishna chowdary <schowdary@...dia.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Michael Ellerman <mpe@...erman.id.au>,
        Paul Mackerras <paulus@...ba.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        "David S. Miller" <davem@...emloft.net>,
        Vineet Gupta <vgupta@...opsys.com>,
        James Hogan <jhogan@...nel.org>,
        Paul Burton <paul.burton@...s.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Gerald Schaefer <gerald.schaefer@...ibm.com>,
        Christophe Leroy <christophe.leroy@....fr>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        linux-snps-arc@...ts.infradead.org, linux-mips@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-ia64@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V6 0/2] mm/debug: Add tests validating architecture page
 table helpers



On 10/16/2019 12:12 AM, Qian Cai wrote:
> On Tue, 2019-10-15 at 20:51 +0530, Anshuman Khandual wrote:
>>
>> On 10/15/2019 08:11 PM, Qian Cai wrote:
>>> The x86 will crash with linux-next during boot due to this series (v5) with the
>>> config below plus CONFIG_DEBUG_VM_PGTABLE=y. I am not sure if v6 would address
>>> it.
>>>
>>> https://raw.githubusercontent.com/cailca/linux-mm/master/x86.config
>>>
>>> [   33.862600][    T1] page:ffffea0009000000 is uninitialized and poisoned
>>> [   33.862608][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff
>>> ffffff871140][    T1]  ? _raw_spin_unlock_irq+0x27/0x40
>>> [   33.871140][    T1]  ? rest_init+0x307/0x307
>>> [   33.871140][    T1]  kernel_init+0x11/0x139
>>> [   33.871140][    T1]  ? rest_init+0x307/0x307
>>> [   33.871140][    T1]  ret_from_fork+0x27/0x50
>>> [   33.871140][    T1] Modules linked in:
>>> [   33.871140][    T1] ---[ end trace e99d392b0f7befbd ]---
>>> [   33.871140][    T1] RIP: 0010:alloc_gigantic_page_order+0x3fe/0x490
>>
>> Hmm, with defconfig (DEBUG_VM=y and DEBUG_VM_PGTABLE=y) it does not crash but
>> with the config above, it does. Just wondering if it is possible that these
>> pages might not been initialized yet because DEFERRED_STRUCT_PAGE_INIT=y ?
> 
> Yes, this patch works fine.
> 
> diff --git a/init/main.c b/init/main.c
> index 676d8020dd29..591be8f9e8e0 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -1177,7 +1177,6 @@ static noinline void __init kernel_init_freeable(void)
>         workqueue_init();
>  
>         init_mm_internals();
> -       debug_vm_pgtable();
>  
>         do_pre_smp_initcalls();
>         lockup_detector_init();
> @@ -1186,6 +1185,8 @@ static noinline void __init kernel_init_freeable(void)
>         sched_init_smp();
>  
>         page_alloc_init_late();
> +       debug_vm_pgtable();
> +
>         /* Initialize page ext after all struct pages are initialized. */
>         page_ext_init();
> 

Sure, will keep this in mind if we at all end up with memory allocation approach
for this test.

>>
>> [   13.898549][    T1] page:ffffea0005000000 is uninitialized and poisoned
>> [   13.898549][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
>> [   13.898549][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
>> [   13.898549][    T1] page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
>> [   13.898549][    T1] ------------[ cut here ]------------
>> [   13.898549][    T1] kernel BUG at ./include/linux/mm.h:1107!
>> [   13.898549][    T1] invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
>> [   13.898549][    T1] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.4.0-rc3-next-20191015+ #
>