Re: memblock_reserve for unadded region (was: [PATCH] MIPS: loongson64: fix boot failure)
From: Yajun Deng
Date: Tue Jan 16 2024 - 22:17:38 EST
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@xxxxxxxxxxx>
---
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.