linux-kernel - Re: [PATCH] arm64/mm: Delete __init region from memblock.reserved

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Message-ID: <5bf1f2f7-07b6-436e-a5b6-68fa63103858@vivo.com>
Date: Fri, 30 Aug 2024 16:25:28 +0800
From: Rong Qianfeng <11065417@...o.com>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Andrew Morton <akpm@...ux-foundation.org>, Baoquan He <bhe@...hat.com>,
 Petr Tesarik <ptesarik@...e.com>, Baruch Siach <baruch@...s.co.il>,
 "Mike Rapoport (IBM)" <rppt@...nel.org>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 opensource.kernel@...o.com, Rong Qianfeng <rongqianfeng@...o.com>
Subject: Re: [PATCH] arm64/mm: Delete __init region from memblock.reserved


在 2024/8/30 16:14, Ard Biesheuvel 写道:
> Hi Rong,
>
> On Fri, 30 Aug 2024 at 10:00, Rong Qianfeng <rongqianfeng@...o.com> wrote:
>> If CONFIG_ARCH_KEEP_MEMBLOCK is enabled, the memory information in
>> memblock will be retained. We release the __init memory here, and
>> we should also delete the corresponding region in memblock.reserved.
>>
>> Signed-off-by: Rong Qianfeng <rongqianfeng@...o.com>
>> ---
>>   arch/arm64/mm/init.c | 7 +++++++
>>   1 file changed, 7 insertions(+)
>>
>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
>> index bfb10969cbf0..99cfa217e905 100644
>> --- a/arch/arm64/mm/init.c
>> +++ b/arch/arm64/mm/init.c
>> @@ -402,6 +402,13 @@ void __init mem_init(void)
>>
>>   void free_initmem(void)
>>   {
>> +       if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) {
> This is always true on arm64
>
>> +               unsigned long aligned_begin = ALIGN_DOWN((u64)__init_begin, PAGE_SIZE);
>> +               unsigned long aligned_end = ALIGN((u64)__init_end, PAGE_SIZE);
>> +
>> +               memblock_free((void *)aligned_begin, aligned_end - aligned_begin);
>> +       }
>> +
> What does this achieve? The memory is already being reused by the page
> allocator (due to free_reserved_area()), and the memblock allocator is
> no longer usable at this point anyway.
If not,  incorrect information will be visible in
/sys/kernel/debug/memblock/reserved.

Best Regards,
Qianfeng
>
>>          free_reserved_area(lm_alias(__init_begin),
>>                             lm_alias(__init_end),
>>                             POISON_FREE_INITMEM, "unused kernel");