linux-kernel - Re: [PATCH] parisc/mm: preallocate fixmap page tables at init

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Date:   Thu, 3 Aug 2023 14:40:01 +0200
From:   Helge Deller <deller@....de>
To:     Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>
Cc:     Christoph Biedl <linux-kernel.bfrz@...chmal.in-ulm.de>,
        "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
        John David Anglin <dave.anglin@...l.net>,
        linux-parisc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] parisc/mm: preallocate fixmap page tables at init

On 8/3/23 10:48, Vlastimil Babka wrote:
> On 8/3/23 08:24, Mike Rapoport wrote:
>> From: "Mike Rapoport (IBM)" <rppt@...nel.org>
>>
>> Christoph Biedl reported early OOM on recent kernels:
>>
>>      swapper: page allocation failure: order:0, mode:0x100(__GFP_ZERO),
>> nodemask=(null)
>>      CPU: 0 PID: 0 Comm: swapper Not tainted 6.3.0-rc4+ #16
>>      Hardware name: 9000/785/C3600
>>      Backtrace:
>>       [<10408594>] show_stack+0x48/0x5c
>>       [<10e152d8>] dump_stack_lvl+0x48/0x64
>>       [<10e15318>] dump_stack+0x24/0x34
>>       [<105cf7f8>] warn_alloc+0x10c/0x1c8
>>       [<105d068c>] __alloc_pages+0xbbc/0xcf8
>>       [<105d0e4c>] __get_free_pages+0x28/0x78
>>       [<105ad10c>] __pte_alloc_kernel+0x30/0x98
>>       [<10406934>] set_fixmap+0xec/0xf4
>>       [<10411ad4>] patch_map.constprop.0+0xa8/0xdc
>>       [<10411bb0>] __patch_text_multiple+0xa8/0x208
>>       [<10411d78>] patch_text+0x30/0x48
>>       [<1041246c>] arch_jump_label_transform+0x90/0xcc
>>       [<1056f734>] jump_label_update+0xd4/0x184
>>       [<1056fc9c>] static_key_enable_cpuslocked+0xc0/0x110
>>       [<1056fd08>] static_key_enable+0x1c/0x2c
>>       [<1011362c>] init_mem_debugging_and_hardening+0xdc/0xf8
>>       [<1010141c>] start_kernel+0x5f0/0xa98
>>       [<10105da8>] start_parisc+0xb8/0xe4
>>
>>      Mem-Info:
>>      active_anon:0 inactive_anon:0 isolated_anon:0
>>       active_file:0 inactive_file:0 isolated_file:0
>>       unevictable:0 dirty:0 writeback:0
>>       slab_reclaimable:0 slab_unreclaimable:0
>>       mapped:0 shmem:0 pagetables:0
>>       sec_pagetables:0 bounce:0
>>       kernel_misc_reclaimable:0
>>       free:0 free_pcp:0 free_cma:0
>>      Node 0 active_anon:0kB inactive_anon:0kB active_file:0kB
>> inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB
>> mapped:0kB dirty:0kB writeback:0kB shmem:0kB
>> +writeback_tmp:0kB kernel_stack:0kB pagetables:0kB sec_pagetables:0kB
>> all_unreclaimable? no
>>      Normal free:0kB boost:0kB min:0kB low:0kB high:0kB
>> reserved_highatomic:0KB active_anon:0kB inactive_anon:0kB active_file:0kB
>> inactive_file:0kB unevictable:0kB writepending:0kB
>> +present:1048576kB managed:1039360kB mlocked:0kB bounce:0kB free_pcp:0kB
>> local_pcp:0kB free_cma:0kB
>>      lowmem_reserve[]: 0 0
>>      Normal: 0*4kB 0*8kB 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB
>> 0*1024kB 0*2048kB 0*4096kB = 0kB
>>      0 total pagecache pages
>>      0 pages in swap cache
>>      Free swap  = 0kB
>>      Total swap = 0kB
>>      262144 pages RAM
>>      0 pages HighMem/MovableOnly
>>      2304 pages reserved
>>      Backtrace:
>>       [<10411d78>] patch_text+0x30/0x48
>>       [<1041246c>] arch_jump_label_transform+0x90/0xcc
>>       [<1056f734>] jump_label_update+0xd4/0x184
>>       [<1056fc9c>] static_key_enable_cpuslocked+0xc0/0x110
>>       [<1056fd08>] static_key_enable+0x1c/0x2c
>>       [<1011362c>] init_mem_debugging_and_hardening+0xdc/0xf8
>>       [<1010141c>] start_kernel+0x5f0/0xa98
>>       [<10105da8>] start_parisc+0xb8/0xe4
>>
>>      Kernel Fault: Code=15 (Data TLB miss fault) at addr 0f7fe3c0
>>      CPU: 0 PID: 0 Comm: swapper Not tainted 6.3.0-rc4+ #16
>>      Hardware name: 9000/785/C3600
>>
>> This happens because patching static key code temporarily maps it via
>> fixmap and if it happens before page allocator is initialized set_fixmap()
>> cannot allocate memory using pte_alloc_kernel().
>>
>> Make sure that fixmap page tables are preallocated early so that
>> pte_offset_kernel() in set_fixmap() never resorts to pte allocation.
>>
>> Signed-off-by: Mike Rapoport (IBM) <rppt@...nel.org>
>
> Acked-by: Vlastimil Babka <vbabka@...e.cz>
>
> ..
> But if it's manifesting for whatever reason since 6.4 then a "Cc: stable #
> 6.4+" would be in order.

Thanks Vlastimil!
I've added your Acked-by and the Cc...

Helge