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

[Helge Deller]

On 8/3/23 10:48, Vlastimil Babka wrote:
> On 8/3/23 08:24, Mike Rapoport wrote:
> > From: "Mike Rapoport (IBM)" <rppt@xxxxxxxxxx>
> >
> > 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@xxxxxxxxxx>
>
> Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
>
> ..
> 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