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

From: Anshuman Khandual <anshuman.khandual@arm.com>
To: Qian Cai <cai@lca.pw>, linux-mm@kvack.org
Cc: Mark Rutland <mark.rutland@arm.com>,
	linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org,
	Peter Zijlstra <peterz@infradead.org>,
	James Hogan <jhogan@kernel.org>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	Michal Hocko <mhocko@kernel.org>,
	Dave Hansen <dave.hansen@intel.com>,
	Paul Mackerras <paulus@samba.org>,
	sparclinux@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
	linux-s390@vger.kernel.org, Jason Gunthorpe <jgg@ziepe.ca>,
	Michael Ellerman <mpe@ellerman.id.au>,
	x86@kernel.org, Russell King - ARM Linux <linux@armlinux.org.uk>,
	Matthew Wilcox <willy@infradead.org>,
	Steven Price <Steven.Price@arm.com>,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	Gerald Schaefer <gerald.schaefer@de.ibm.com>,
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	Kees Cook <keescook@chromium.org>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Mark Brown <broonie@kernel.org>,
	"Kirill A . Shutemov" <kirill@shutemov.name>,
	Dan Williams <dan.j.williams@intel.com>,
	Vlastimil Babka <vbabka@suse.cz>,
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	Mike Rapoport <rppt@linux.vnet.ibm.com>,
	Vineet Gupta <vgupta@synopsys.com>,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
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	"David S. Miller" <davem@davemloft.net>,
	Mike Kravetz <mike.kravetz@oracle.com>
Subject: Re: [PATCH V6 0/2] mm/debug: Add tests validating architecture page table helpers
Date: Wed, 16 Oct 2019 09:11:59 +0000	[thread overview]
Message-ID: <fb1fe447-d30a-21ea-1b85-0d46e14f0872@arm.com> (raw)
In-Reply-To: <1571164920.5937.45.camel@lca.pw>

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+ #
> 