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Message-ID: <Zae1QDqgr6jJsLTQ@kernel.org>
Date: Wed, 17 Jan 2024 13:08:48 +0200
From: Mike Rapoport <rppt@...nel.org>
To: Huang Pei <huangpei@...ngson.cn>
Cc: Yajun Deng <yajun.deng@...ux.dev>,
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 Wed, Jan 17, 2024 at 03:45:46PM +0800, Huang Pei wrote:
> On Wed, Jan 17, 2024 at 08:46:34AM +0200, Mike Rapoport wrote:
> > On Wed, Jan 17, 2024 at 11:59:10AM +0800, Huang Pei wrote:
> > > On Wed, Jan 17, 2024 at 11:17:18AM +0800, Yajun Deng wrote:
> > > >
> > > > 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;
> >
> > IMO this will fix the bug. Before 61167ad5fecd we had nid = first_online_node
> > for reserved pages that didn't have nid set in memblock.reserved. After
> > 61167ad5fecd we try to initialize these pages with MAX_NUMNODES and
> > obviously crash when accessing node structure.
> >
> > I think that the check for a valid nid should be moved to
> > memmap_init_reserved_pages() though. An entire reserved region will have
> > nid set to MAX_NUMNODES, so there is no point to check every page in it.
> >
> > > > > I do not think this fix set the right nid, ONLY arch/platform know that
> > > > > nid
> >
> > Why does it matter to have the right nid in a reserved page that is not
> > part of usable memory?
> >
> IMO, if a reserved page DO have a valid nid, and archs knows that, archs
> should set it right, and this is just the case of loongson64(and
> loongarch).
An arch may choose to set nids for reserved regions that are never added to
memblock.memory, but mm shouldn't crash if it didn't.
> > That's true that only arch knows on which node those reserved pages are,
> > but core mm does not care about reserved pages that are not in memory.
> >
> > > > > 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?
> > >
> > > Yes, more accurately, this bug is exposed by commit 61167ad5fecd. My
> > > previous fix is based on presumptions that memory_reserve should reserve memory
> > > added by memblock_add{,_node}, if going across this limitation, there need
> > > to set the valid nid for reserved memory region.
> > > >
> > > > > >
> > > > > > > > > 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.
> > >
> >
> > --
> > Sincerely yours,
> > Mike.
>
--
Sincerely yours,
Mike.
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