linux-kernel - Re: [PATCH v2 03/11] mm/damon/paddr: support addr_unit for DAMOS

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Message-ID: <c8c3d0d5-e9e1-44de-8722-1e7d09786b51@huawei.com>
Date: Wed, 27 Aug 2025 10:21:41 +0800
From: Quanmin Yan <yanquanmin1@...wei.com>
To: SeongJae Park <sj@...nel.org>
CC: <akpm@...ux-foundation.org>, <damon@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
	<wangkefeng.wang@...wei.com>, <zuoze1@...wei.com>, <kernel-team@...a.com>,
	kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v2 03/11] mm/damon/paddr: support addr_unit for
 DAMOS_PAGEOUT


在 2025/8/26 22:21, SeongJae Park 写道:
> On Tue, 26 Aug 2025 12:51:17 +0800 Quanmin Yan <yanquanmin1@...wei.com> wrote:
>
>> Hi SJ,
>>
>> 在 2025/8/26 11:21, SeongJae Park 写道:
>>> [...]
>>>
>>>>> ==== Attachment 0 (0001-mm-damon-paddr-use-do_div-on-i386-for-damon_pa_pageo.patch) ====
>>>>>    From hackermail Thu Jan  1 00:00:00 1970
>>>>> From: SeongJae Park <sj@...nel.org>
>>>>> To: Andrew Morton <akpm@...ux-foundation.org>
>>>>> Cc: SeongJae Park <sj@...nel.org>
>>>>> Cc: damon@...ts.linux.dev
>>>>> Cc: kernel-team@...a.com
>>>>> Cc: linux-kernel@...r.kernel.org
>>>>> Cc: linux-mm@...ck.org
>>>>> Date: Mon, 25 Aug 2025 07:41:33 -0700
>>>>> Subject: [PATCH 1/3] mm/damon/paddr: use do_div() on i386 for damon_pa_pageout()
>>>>>             return value
>>>>>
>>>>> Otherwise, __udidi3 linking problem happens on certain configs.
>>>>>
>>>>> Reported-by: kernel test robot <lkp@...el.com>
>>>>> Closes: https://lore.kernel.org/oe-kbuild-all/202508241831.EKwdwXZL-lkp@intel.com/
>>>>> Signed-off-by: SeongJae Park <sj@...nel.org>
>>>>> ---
>>>>>     mm/damon/paddr.c | 14 +++++++++++++-
>>>>>     1 file changed, 13 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
>>>>> index 5fad2f9a99a0..09c87583af6c 100644
>>>>> --- a/mm/damon/paddr.c
>>>>> +++ b/mm/damon/paddr.c
>>>>> @@ -135,6 +135,18 @@ static bool damon_pa_invalid_damos_folio(struct folio *folio, struct damos *s)
>>>>>     	return false;
>>>>>     }
>>>>>     
>>>>> +/* convert physical address to core-layer address */
>>>>> +static unsigned long damon_pa_core_addr(phys_addr_t pa,
>>>>> +		unsigned long addr_unit)
>>>>> +{
>>>>> +#ifdef __i386__
>>>> Can we use the following condition instead?
>>>>
>>>> #if !defined(CONFIG_64BIT) && defined(CONFIG_PHYS_ADDR_T_64BIT)
>>> To my understanding, this issue happens only on i386, not every 32bit
>>> architectures.  So I think i386 specific condition is better.
>> I understand. However, the aforementioned general condition is essential,
>> and we should propose a new patch to address this. After introducing addr_unit,
>> any 32-bit architecture should support monitoring of 64-bit phys_addr_t.
> The issue is that we cannot divide 64bit values with plain '/' operator on
> "i386", and hence this patch makes it to use do_div() instead of '/' on "i386".
> No such or other problems at supporting 64-bit phys_addr_t is found on other
> 32bit architectures, to my understanding.  My understanding is that at least
> you confirmed that on your arm-based test environment.  So we don't need a new
> patch to my understanding.
>
> Am I missing somthing?

This is because I seem to have made a mistake earlier: I adjusted the local
compilation toolchain. When the __udivdi3 issue mentioned above occurred, it
reminded me of a potential problem. After switching to a completely new environment
for testing, I discovered the __aeabi_uldivmod linking error in arm, which is similar
to the __udivdi3 issue.🙁 To prevent similar environment-related problems in the
future, I suggest adjusting the condition to the following:

#if !defined(CONFIG_64BIT) && defined(CONFIG_PHYS_ADDR_T_64BIT)

Please consider approving this fix.


Best regards,
Quanmin Yan


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