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SubjectRe: [PATCH v2 RESEND 1/2] arm, arm64: change_memory_common with numpages == 0 should be no-op.
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Hi Will,

On 26.01.2016 17:59, Will Deacon wrote:
> Hi Mika,
>
> On Tue, Jan 26, 2016 at 04:59:52PM +0200, mika.penttila@nextfour.com wrote:
>> From: Mika Penttilä <mika.penttila@nextfour.com>
>>
>> This makes the caller set_memory_xx() consistent with x86.
>>
>> arm64 part is rebased on 4.5.0-rc1 with Ard's patch
>> lkml.kernel.org/g/<1453125665-26627-1-git-send-email-ard.biesheuvel@linaro.org>
>> applied.
>>
>> Signed-off-by: Mika Penttilä mika.penttila@nextfour.com
>> Reviewed-by: Laura Abbott <labbott@redhat.com>
>> Acked-by: David Rientjes <rientjes@google.com>
>>
>> ---
>> arch/arm/mm/pageattr.c | 3 +++
>> arch/arm64/mm/pageattr.c | 3 +++
>> 2 files changed, 6 insertions(+)
>>
>> diff --git a/arch/arm/mm/pageattr.c b/arch/arm/mm/pageattr.c
>> index cf30daf..d19b1ad 100644
>> --- a/arch/arm/mm/pageattr.c
>> +++ b/arch/arm/mm/pageattr.c
>> @@ -49,6 +49,9 @@ static int change_memory_common(unsigned long addr, int numpages,
>> WARN_ON_ONCE(1);
>> }
>>
>> + if (!numpages)
>> + return 0;
>> +
>> if (start < MODULES_VADDR || start >= MODULES_END)
>> return -EINVAL;
>>
>> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
>> index 1360a02..b582fc2 100644
>> --- a/arch/arm64/mm/pageattr.c
>> +++ b/arch/arm64/mm/pageattr.c
>> @@ -53,6 +53,9 @@ static int change_memory_common(unsigned long addr, int numpages,
>> WARN_ON_ONCE(1);
>> }
>>
>> + if (!numpages)
>> + return 0;
>> +
> Thanks for this. I can reproduce the failure on my Juno board, so I'd
> like to queue this for 4.5 since it fixes a real issue. I've taken the
> liberty of rebasing the arm64 part to my fixes branch and writing a
> commit message. Does the patch below look ok to you?
>
> Will
>
> --->8
>
> From 57adec866c0440976c96a4b8f5b59fb411b1cacb Mon Sep 17 00:00:00 2001
> From: =?UTF-8?q?Mika=20Penttil=C3=A4?= <mika.penttila@nextfour.com>
> Date: Tue, 26 Jan 2016 15:47:25 +0000
> Subject: [PATCH] arm64: mm: avoid calling apply_to_page_range on empty range
> MIME-Version: 1.0
> Content-Type: text/plain; charset=UTF-8
> Content-Transfer-Encoding: 8bit
>
> Calling apply_to_page_range with an empty range results in a BUG_ON
> from the core code. This can be triggered by trying to load the st_drv
> module with CONFIG_DEBUG_SET_MODULE_RONX enabled:
>
> kernel BUG at mm/memory.c:1874!
> Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
> Modules linked in:
> CPU: 3 PID: 1764 Comm: insmod Not tainted 4.5.0-rc1+ #2
> Hardware name: ARM Juno development board (r0) (DT)
> task: ffffffc9763b8000 ti: ffffffc975af8000 task.ti: ffffffc975af8000
> PC is at apply_to_page_range+0x2cc/0x2d0
> LR is at change_memory_common+0x80/0x108
>
> This patch fixes the issue by making change_memory_common (called by the
> set_memory_* functions) a NOP when numpages == 0, therefore avoiding the
> erroneous call to apply_to_page_range and bringing us into line with x86
> and s390.
>
> Cc: <stable@vger.kernel.org>
> Reviewed-by: Laura Abbott <labbott@redhat.com>
> Acked-by: David Rientjes <rientjes@google.com>
> Signed-off-by: Mika Penttilä <mika.penttila@nextfour.com>
> Signed-off-by: Will Deacon <will.deacon@arm.com>
> ---
> arch/arm64/mm/pageattr.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
> index 3571c7309c5e..cf6240741134 100644
> --- a/arch/arm64/mm/pageattr.c
> +++ b/arch/arm64/mm/pageattr.c
> @@ -57,6 +57,9 @@ static int change_memory_common(unsigned long addr, int numpages,
> if (end < MODULES_VADDR || end >= MODULES_END)
> return -EINVAL;
>
> + if (!numpages)
> + return 0;
> +
> data.set_mask = set_mask;
> data.clear_mask = clear_mask;
>

Yes I'm fine with that,
Thanks!
Mika

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