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().
> 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?
> 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.
