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Date: Wed, 17 Jan 2024 11:17:18 +0800
From: Yajun Deng <yajun.deng@...ux.dev>
To: Huang Pei <huangpei@...ngson.cn>
Cc: Mike Rapoport <rppt@...nel.org>, Jiaxun Yang <jiaxun.yang@...goat.com>,
linux-mm@...ck.org, Bibo Mao <maobibo@...ngson.cn>,
linux-mips@...r.kernel.org, Paul Burton <paulburton@...nel.org>,
Li Xuefeng <lixuefeng@...ngson.cn>, Yang Tiezhu <yangtiezhu@...ngson.cn>,
Gao Juxin <gaojuxin@...ngson.cn>, Huacai Chen <chenhuacai@...ngson.cn>,
Thomas Bogendoerfer <tsbogend@...ha.franken.de>, linux-kernel@...r.kernel.org
Subject: Re: memblock_reserve for unadded region (was: [PATCH] MIPS:
loongson64: fix boot failure)
On 2024/1/17 11:01, Huang Pei wrote:
> On Wed, Jan 17, 2024 at 10:20:00AM +0800, Yajun Deng wrote:
>> On 2024/1/16 20:23, Huang Pei wrote:
>>> On Tue, Jan 16, 2024 at 10:39:04AM +0200, Mike Rapoport wrote:
>>>> On Mon, Jan 15, 2024 at 02:08:21PM +0000, Jiaxun Yang wrote:
>>>>> Hi mm folks,
>>>>>
>>>>> Just a quick question, what is the expected behavior of memblock_reserve
>>>>> a region that is not added to memblock with memblock_add?
>>>>>
>>>>> I'm unable to find any documentation about memblock_reserve in comments and
>>>>> boot-time-mm, but as per my understanding to the code, this should be a
>>>>> legit usage?
>>>> Yes, memblock allows reserving memory that was not added to memblock with
>>>> memblock_add().
>>> I think arch/platform specific code should fix this bug, like,
>>> --------------------------------------------------------------------------
>>> //for loongson64
>>> memblock_set_node(0, 1ULL << 44, &memblock.reserved, 0);
>>>
>>> --------------------------------------------------------------------------
>>>
>>> or maybe memblock provide something like memblock_reserve_node
>> Hi pei,
>>
>> Can you test the following patch to see if it fixes this bug?
>>
>> diff --git a/mm/mm_init.c b/mm/mm_init.c
>> index 2c19f5515e36..97721d99fdce 100644
>> --- a/mm/mm_init.c
>> +++ b/mm/mm_init.c
>> @@ -708,6 +708,9 @@ static void __meminit init_reserved_page(unsigned long
>> pfn, int nid)
>> pg_data_t *pgdat;
>> int zid;
>>
>> + if (unlikely(nid == NUMA_NO_NODE || nid >= MAX_NUMNODES))
>> + nid = early_pfn_to_nid(pfn);
>> +
>> if (early_page_initialised(pfn, nid))
>> return;
> I do not think this fix set the right nid, ONLY arch/platform know that
> nid
>
> int __meminit early_pfn_to_nid(unsigned long pfn)
> {
> static DEFINE_SPINLOCK(early_pfn_lock);
> int nid;
>
> spin_lock(&early_pfn_lock);
> nid = __early_pfn_to_nid(pfn,
> &early_pfnnid_cache);
> if (nid < 0)
> //!!!first_online_node MAY NOT be the node the pfn belong to!!!
> nid = first_online_node;
>
> spin_unlock(&early_pfn_lock);
>
> return
> nid;
> }
Okay, I don't think this bug is caused by commit 61167ad5fecd ("mm: pass
nid to reserve_bootmem_region()"),
because even if you revert this commit, it will still get nid by
early_pfn_to_nid(). Did I get that right?
>>
>>>>> In practical we run into uninitialized nid of reserved block problem, should
>>>>> we fix it
>>>>> in our usage, or on memblock side?
>>>> Apparently it's a bug in memblock :(
>>>>
>>>> If you revert 61167ad5fecd ("mm: pass nid to reserve_bootmem_region()")
>>>> does the issue disappear?
>>> Yes, I git bisect this commit.
>>>
>>> But I don't think it is a bug in memblock. IMO, memblock_reserve under
>>> NUMA set nid of reserved region to MAX_NUMNODES, which is the point
>>> that cause the "memblock_get_region_node from memmap_init_reserved_pages "
>>> passing a invalid node id(aka MAX_NUMNODES) to "reserver_bootmem_region
>>> -> init_reserved_page -> early_pfn_to_nid". If arch-specific code DOES NOT
>>> initialize the nid of reserved region(only it know that), or the reserved
>>> region NOT within a memblock added by memblock_add, memblock can not
>>> give a valid node id to the reserved region. Commit 61167ad5fecd ("mm: pass nid to
>>> reserve_bootmem_region()") just reveals the embarrassment case by an
>>> out of bound memory access.
>>>
>>>>> Thanks
>>>>>
>>>>> 在 2023/12/25 09:30, Huang Pei 写道:
>>>>>> Since commit 61167ad5fecd("mm: pass nid to reserve_bootmem_region()),
>>>>>> loongson64 booting failed with CONFIG_DEFERRED_STRUCT_PAGE_INIT like
>>>>>> this:
>>>>>> ----------------------------------------------------------------------
>>>>>> Call Trace:
>>>>>> [<ffffffff8235d088>] reserve_bootmem_region+0xa8/0x184
>>>>>> [<ffffffff82333940>] memblock_free_all+0x104/0x2a8
>>>>>> [<ffffffff8231d8e4>] mem_init+0x84/0x94
>>>>>> [<ffffffff82330958>] mm_core_init+0xf8/0x308
>>>>>> [<ffffffff82318c38>] start_kernel+0x43c/0x86c
>>>>>>
>>>>>> Code: 10400028 2402fff0 de420000 <dc432880> 0203182b 14600022
>>>>>> 64420070 00003025 24040003
>>>>>>
>>>>>> ---[ end trace 0000000000000000 ]---
>>>>>> Kernel panic - not syncing: Attempted to kill the idle task!
>>>>>> ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]---
>>>>>> ----------------------------------------------------------------------
>>>>>>
>>>>>> The root cause is no memory region "0x0-0x1fffff" paired with
>>>>>> memory-reserved region "0x0-0x1fffff" and "0x0-0xfff", with "memblock
>>>>>> =debug":
>>>>>>
>>>>>> ----------------------------------------------------------------------
>>>>>> memory[0x0] [0x0000000000200000-0x000000000effffff],
>>>>>> 0x000000000ee00000 bytes on node 0 flags: 0x0 !!!!here
>>>>>> memory[0x1] [0x0000000090000000-0x00000000fdffffff],
>>>>>> 0x000000006e000000 bytes on node 0 flags: 0x0
>>>>>> memory[0x2] [0x0000000100000000-0x000000027fffffff],
>>>>>> 0x0000000180000000 bytes on node 0 flags: 0x0
>>>>>> memory[0x3] [0x0000100000000000-0x000010000fffffff],
>>>>>> 0x0000000010000000 bytes on node 1 flags: 0x0
>>>>>> memory[0x4] [0x0000100090000000-0x000010027fffffff],
>>>>>> 0x00000001f0000000 bytes on node 1 flags: 0x0
>>>>>> reserved.cnt = 0x1f
>>>>>> reserved[0x0] [0x0000000000000000-0x000000000190c80a],
>>>>>> 0x000000000190c80b bytes flags: 0x0 !!!!oops 0x0-0x1fffff not in memory[0]
>>>>>> reserved[0x1] [0x000000000190c810-0x000000000190eea3],
>>>>>> 0x0000000000002694 bytes flags: 0x0
>>>>>> ----------------------------------------------------------------------
>>>>>>
>>>>>> It caused memory-reserved region "0x0-0x1fffff" without valid node id
>>>>>> in "memblock_get_region_node" from "memmap_init_reserved_pages", lead to
>>>>>> "reserve_bootmem_region-> init_reserved_page -> early_pfn_to_nid()"
>>>>>> accessing "node_data" out of bound.
>>>>>>
>>>>>> To fix this bug, we should remove unnecessary memory block reservation.
>>>>>>
>>>>>> +. no need to reserve 0x0-0x1fffff below kernel loading address, since
>>>>>> it is not registered by "memblock_add_node"
>>>>>>
>>>>>> +. no need to reserve 0x0-0xfff for exception handling if it is not
>>>>>> registered by "memblock_add" either.
>>>>>>
>>>>>> Fixes: commit 61167ad5fecd("mm: pass nid to reserve_bootmem_region())
>>>>>> Signed-off-by: Huang Pei <huangpei@...ngson.cn>
>>>>>> ---
>>>>>> arch/mips/kernel/traps.c | 3 ++-
>>>>>> arch/mips/loongson64/numa.c | 2 --
>>>>>> 2 files changed, 2 insertions(+), 3 deletions(-)
>>>>>>
>>>>>> diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
>>>>>> index 246c6a6b0261..9b632b4c10c3 100644
>>>>>> --- a/arch/mips/kernel/traps.c
>>>>>> +++ b/arch/mips/kernel/traps.c
>>>>>> @@ -2007,7 +2007,8 @@ unsigned long vi_handlers[64];
>>>>>> void reserve_exception_space(phys_addr_t addr, unsigned long size)
>>>>>> {
>>>>>> - memblock_reserve(addr, size);
>>>>>> + if(memblock_is_region_memory(addr, size))
>>>>>> + memblock_reserve(addr, size);
>>>>>> }
>>>>>> void __init *set_except_vector(int n, void *addr)
>>>>>> diff --git a/arch/mips/loongson64/numa.c b/arch/mips/loongson64/numa.c
>>>>>> index 8f61e93c0c5b..0f516dde81da 100644
>>>>>> --- a/arch/mips/loongson64/numa.c
>>>>>> +++ b/arch/mips/loongson64/numa.c
>>>>>> @@ -130,8 +130,6 @@ static void __init node_mem_init(unsigned int node)
>>>>>> memblock_reserve((node_addrspace_offset | 0xfe000000),
>>>>>> 32 << 20);
>>>>>> - /* Reserve pfn range 0~node[0]->node_start_pfn */
>>>>>> - memblock_reserve(0, PAGE_SIZE * start_pfn);
>>>>>> }
>>>>>> }
>>>>> --
>>>>> ---
>>>>> Jiaxun Yang
>>>>>
>>>> --
>>>> Sincerely yours,
>>>> Mike.
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