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From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Will Deacon <will.deacon@arm.com>
Cc: "linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Hanjun Guo <hanjun.guo@linaro.org>,
	Yisheng Xie <xieyisheng1@huawei.com>,
	Robert Richter <rrichter@cavium.com>,
	James Morse <james.morse@arm.com>
Subject: Re: [PATCH 2/2] arm64: mm: enable CONFIG_HOLES_IN_ZONE for NUMA
Date: Wed, 4 Jan 2017 13:50:20 +0000	[thread overview]
Message-ID: <CAKv+Gu8MdpVDCSjfum7AMtbgR6cTP5H+67svhDSu6bkaijvvyg@mail.gmail.com> (raw)
In-Reply-To: <20170104132831.GD18193@arm.com>

On 4 January 2017 at 13:28, Will Deacon <will.deacon@arm.com> wrote:
> On Wed, Dec 14, 2016 at 09:11:47AM +0000, Ard Biesheuvel wrote:
>> The NUMA code may get confused by the presence of NOMAP regions within
>> zones, resulting in spurious BUG() checks where the node id deviates
>> from the containing zone's node id.
>>
>> Since the kernel has no business reasoning about node ids of pages it
>> does not own in the first place, enable CONFIG_HOLES_IN_ZONE to ensure
>> that such pages are disregarded.
>>
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> ---
>>  arch/arm64/Kconfig | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index 111742126897..0472afe64d55 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -614,6 +614,10 @@ config NEED_PER_CPU_EMBED_FIRST_CHUNK
>>       def_bool y
>>       depends on NUMA
>>
>> +config HOLES_IN_ZONE
>> +     def_bool y
>> +     depends on NUMA
>> +
>>  source kernel/Kconfig.preempt
>>  source kernel/Kconfig.hz
>
> I'm happy to apply this, but I'll hold off until the first patch is queued
> somewhere, since this doesn't help without the VM_BUG_ON being moved.
>
> Alternatively, I can queue both if somebody from the mm camp acks the
> first patch.
>

Actually, I am not convinced the discussion is finalized. These
patches do fix the issue, but Robert also suggested an alternative fix
which may be preferable.

http://marc.info/?l=linux-arm-kernel&m=148190753510107&w=2

I haven't responded to it yet, due to the holidays, but I'd like to
explore that solution a bit further before applying anything, if you
don't mind.

Thanks,
Ard.

WARNING: multiple messages have this Message-ID (diff)
From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Will Deacon <will.deacon@arm.com>
Cc: "linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Hanjun Guo <hanjun.guo@linaro.org>,
	Yisheng Xie <xieyisheng1@huawei.com>,
	Robert Richter <rrichter@cavium.com>,
	James Morse <james.morse@arm.com>
Subject: Re: [PATCH 2/2] arm64: mm: enable CONFIG_HOLES_IN_ZONE for NUMA
Date: Wed, 4 Jan 2017 13:50:20 +0000	[thread overview]
Message-ID: <CAKv+Gu8MdpVDCSjfum7AMtbgR6cTP5H+67svhDSu6bkaijvvyg@mail.gmail.com> (raw)
In-Reply-To: <20170104132831.GD18193@arm.com>

On 4 January 2017 at 13:28, Will Deacon <will.deacon@arm.com> wrote:
> On Wed, Dec 14, 2016 at 09:11:47AM +0000, Ard Biesheuvel wrote:
>> The NUMA code may get confused by the presence of NOMAP regions within
>> zones, resulting in spurious BUG() checks where the node id deviates
>> from the containing zone's node id.
>>
>> Since the kernel has no business reasoning about node ids of pages it
>> does not own in the first place, enable CONFIG_HOLES_IN_ZONE to ensure
>> that such pages are disregarded.
>>
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> ---
>>  arch/arm64/Kconfig | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index 111742126897..0472afe64d55 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -614,6 +614,10 @@ config NEED_PER_CPU_EMBED_FIRST_CHUNK
>>       def_bool y
>>       depends on NUMA
>>
>> +config HOLES_IN_ZONE
>> +     def_bool y
>> +     depends on NUMA
>> +
>>  source kernel/Kconfig.preempt
>>  source kernel/Kconfig.hz
>
> I'm happy to apply this, but I'll hold off until the first patch is queued
> somewhere, since this doesn't help without the VM_BUG_ON being moved.
>
> Alternatively, I can queue both if somebody from the mm camp acks the
> first patch.
>

Actually, I am not convinced the discussion is finalized. These
patches do fix the issue, but Robert also suggested an alternative fix
which may be preferable.

http://marc.info/?l=linux-arm-kernel&m=148190753510107&w=2

I haven't responded to it yet, due to the holidays, but I'd like to
explore that solution a bit further before applying anything, if you
don't mind.

Thanks,
Ard.

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WARNING: multiple messages have this Message-ID (diff)
From: ard.biesheuvel@linaro.org (Ard Biesheuvel)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 2/2] arm64: mm: enable CONFIG_HOLES_IN_ZONE for NUMA
Date: Wed, 4 Jan 2017 13:50:20 +0000	[thread overview]
Message-ID: <CAKv+Gu8MdpVDCSjfum7AMtbgR6cTP5H+67svhDSu6bkaijvvyg@mail.gmail.com> (raw)
In-Reply-To: <20170104132831.GD18193@arm.com>

On 4 January 2017 at 13:28, Will Deacon <will.deacon@arm.com> wrote:
> On Wed, Dec 14, 2016 at 09:11:47AM +0000, Ard Biesheuvel wrote:
>> The NUMA code may get confused by the presence of NOMAP regions within
>> zones, resulting in spurious BUG() checks where the node id deviates
>> from the containing zone's node id.
>>
>> Since the kernel has no business reasoning about node ids of pages it
>> does not own in the first place, enable CONFIG_HOLES_IN_ZONE to ensure
>> that such pages are disregarded.
>>
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> ---
>>  arch/arm64/Kconfig | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index 111742126897..0472afe64d55 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -614,6 +614,10 @@ config NEED_PER_CPU_EMBED_FIRST_CHUNK
>>       def_bool y
>>       depends on NUMA
>>
>> +config HOLES_IN_ZONE
>> +     def_bool y
>> +     depends on NUMA
>> +
>>  source kernel/Kconfig.preempt
>>  source kernel/Kconfig.hz
>
> I'm happy to apply this, but I'll hold off until the first patch is queued
> somewhere, since this doesn't help without the VM_BUG_ON being moved.
>
> Alternatively, I can queue both if somebody from the mm camp acks the
> first patch.
>

Actually, I am not convinced the discussion is finalized. These
patches do fix the issue, but Robert also suggested an alternative fix
which may be preferable.

http://marc.info/?l=linux-arm-kernel&m=148190753510107&w=2

I haven't responded to it yet, due to the holidays, but I'd like to
explore that solution a bit further before applying anything, if you
don't mind.

Thanks,
Ard.

  reply	other threads:[~2017-01-04 13:51 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-14  9:11 [PATCH 0/2] arm64: numa: fix spurious BUG() on NOMAP regions Ard Biesheuvel
2016-12-14  9:11 ` Ard Biesheuvel
2016-12-14  9:11 ` Ard Biesheuvel
2016-12-14  9:11 ` [PATCH 1/2] mm: don't dereference struct page fields of invalid pages Ard Biesheuvel
2016-12-14  9:11   ` Ard Biesheuvel
2016-12-14  9:11   ` Ard Biesheuvel
2017-01-04 12:16   ` Will Deacon
2017-01-04 12:16     ` Will Deacon
2017-01-04 12:16     ` Will Deacon
2016-12-14  9:11 ` [PATCH 2/2] arm64: mm: enable CONFIG_HOLES_IN_ZONE for NUMA Ard Biesheuvel
2016-12-14  9:11   ` Ard Biesheuvel
2016-12-14  9:11   ` Ard Biesheuvel
2016-12-15 15:39   ` Robert Richter
2016-12-15 15:39     ` Robert Richter
2016-12-15 15:39     ` Robert Richter
2016-12-15 16:07     ` Ard Biesheuvel
2016-12-15 16:07       ` Ard Biesheuvel
2016-12-15 16:07       ` Ard Biesheuvel
2016-12-16 17:10       ` Robert Richter
2016-12-16 17:10         ` Robert Richter
2016-12-16 17:10         ` Robert Richter
2016-12-16  1:57     ` Hanjun Guo
2016-12-16  1:57       ` Hanjun Guo
2016-12-16  1:57       ` Hanjun Guo
2016-12-16 17:14       ` Robert Richter
2016-12-16 17:14         ` Robert Richter
2016-12-16 17:14         ` Robert Richter
2017-01-04 13:28   ` Will Deacon
2017-01-04 13:28     ` Will Deacon
2017-01-04 13:28     ` Will Deacon
2017-01-04 13:50     ` Ard Biesheuvel [this message]
2017-01-04 13:50       ` Ard Biesheuvel
2017-01-04 13:50       ` Ard Biesheuvel
2017-01-04 14:02       ` Will Deacon
2017-01-04 14:02         ` Will Deacon
2017-01-04 14:02         ` Will Deacon
2017-01-05 11:24         ` Robert Richter
2017-01-05 11:24           ` Robert Richter
2017-01-05 11:24           ` Robert Richter
2017-01-05 12:08           ` Will Deacon
2017-01-05 12:08             ` Will Deacon
2017-01-05 12:08             ` Will Deacon
2017-01-05 12:22             ` Robert Richter
2017-01-05 12:22               ` Robert Richter
2017-01-05 12:22               ` Robert Richter
2017-01-05 19:49               ` Robert Richter
2017-01-05 19:49                 ` Robert Richter
2017-01-05 19:49                 ` Robert Richter
2017-01-06 12:03                 ` Will Deacon
2017-01-06 12:03                   ` Will Deacon
2017-01-06 12:03                   ` Will Deacon
2017-01-06 12:22                   ` Ard Biesheuvel
2017-01-06 12:22                     ` Ard Biesheuvel
2017-01-06 12:22                     ` Ard Biesheuvel
2017-02-06 13:36   ` Robert Richter
2017-02-06 13:36     ` Robert Richter
2017-02-06 13:36     ` Robert Richter

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