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

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Message-Id: <20250826142155.53632-1-sj@kernel.org>
Date: Tue, 26 Aug 2025 07:21:55 -0700
From: SeongJae Park <sj@...nel.org>
To: Quanmin Yan <yanquanmin1@...wei.com>
Cc: SeongJae Park <sj@...nel.org>,
	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

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?


Thanks,
SJ

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