From: "David Hildenbrand (Arm)" <david@kernel.org>
To: Dave Young <ruirui.yang@linux.dev>
Cc: David Carlier <devnexen@gmail.com>,
akpm@linux-foundation.org, axelrasmussen@google.com,
baohua@kernel.org, baolin.wang@linux.alibaba.com,
baoquan.he@linux.dev, brendan.jackman@linux.dev, dakr@kernel.org,
driver-core@lists.linux.dev, gregkh@linuxfoundation.org,
hannes@cmpxchg.org, jan.kiszka@siemens.com, kasong@tencent.com,
kbingham@kernel.org, liam@infradead.org,
linux-cxl@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org, ljs@kernel.org,
mhocko@suse.com, osalvador@suse.de, qi.zheng@linux.dev,
rafael@kernel.org, rppt@kernel.org, shakeel.butt@linux.dev,
surenb@google.com, vbabka@kernel.org, weixugc@google.com,
yuanchu@google.com, ziy@nvidia.com,
devel@lists.crash-utility.osci.io, kexec@lists.infradead.org,
Baoquan He <baoquan.he@linux.dev>
Subject: Re: [PATCH v2 10/13] mm/sparse: remove SECTION_MARKED_PRESENT
Date: Mon, 28 Sep 2026 10:50:11 +0200 [thread overview]
Message-ID: <9009312f-0ffb-4425-ab82-1eb7e52a4646@kernel.org> (raw)
In-Reply-To: <aroezLexo1WoeYI7@darkstar>
On 9/28/26 10:01, Dave Young wrote:
> Cced kexec list.
>
> On Mon, Sep 28, 2026 at 09:28:08AM +0200, David Hildenbrand (Arm) wrote:
>> On 9/27/26 21:20, David Carlier wrote:
>>>
>>> Hi David,
>>
>> Hi!
>>
>>>
>>> It seems dropping SECTION_MARKED_PRESENT_BIT shifts the other section flags down
>>> one bit. crash hardcodes SECTION_HAS_MEM_MAP as (1UL << 1) in
>>> pfn_to_map(), so it now tests SECTION_IS_ONLINE: offline and
>>> ZONE_DEVICE sections no longer resolve to a struct page. makedumpfile
>>> only checks bit 0 and is fine.
>>
>> Thanks. To be expected when relying on kernel internals.
>>
>> Which makes me wonder why makedumpfile
>> (https://github.com/makedumpfile/makedumpfile) not require any such information.
>>
>>>
>>> Keep bit 0 reserved, or export the bits via vmcoreinfo?
>> We could export it, or crash can simply detect the change based on the kernel
>> version. I remember the latter was done in makedumpfile in the past (although we
>> export it).
>>
>> I can send a separate patch to export it.
>
> Thanks David. Checking kernel internals via kernel version is not a good idea
> due to the downstream kernels.
Patch at:
https://lore.kernel.org/r/20260928-section_has_mem_map-v1-1-4129f6ba2838@kernel.org
--
Cheers,
David
prev parent reply other threads:[~2026-09-28 8:50 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20260921-b4-sparsemem_cleanups-v2-10-54d81d65e125@kernel.org>
[not found] ` <20260927192013.144672-1-devnexen@gmail.com>
[not found] ` <655c509e-318f-48bc-8183-2b1274dd05ac@kernel.org>
2026-09-28 8:01 ` [PATCH v2 10/13] mm/sparse: remove SECTION_MARKED_PRESENT Dave Young
2026-09-28 8:50 ` David Hildenbrand (Arm) [this message]
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