Hi Vlastimil, On Fri, Feb 27, 2026 at 04:14:42PM +0100, Vlastimil Babka wrote: > On 1/11/26 09:20, Mike Rapoport wrote: > > From: "Mike Rapoport (Microsoft)" <[email protected]> > > > > To initialize node, zone and memory map data structures every architecture > > calls free_area_init() during setup_arch() and passes it an array of zone > > limits. > > > > Beside code duplication it creates "interesting" ordering cases between > > allocation and initialization of hugetlb and the memory map. Some > > architectures allocate hugetlb pages very early in setup_arch() in certain > > cases, some only create hugetlb CMA areas in setup_arch() and sometimes > > hugetlb allocations happen mm_core_init(). > > > > With arch_zone_limits_init() helper available now on all architectures it > > is no longer necessary to call free_area_init() from architecture setup > > code. Rather core MM initialization can call arch_zone_limits_init() in a > > single place. > > > > This allows to unify ordering of hugetlb vs memory map allocation and > > initialization. > > > > Remove the call to free_area_init() from architecture specific code and > > place it in a new mm_core_init_early() function that is called immediately > > after setup_arch(). > > > > After this refactoring it is possible to consolidate hugetlb allocations > > and eliminate differences in ordering of hugetlb and memory map > > initialization among different architectures. > > > > As the first step of this consolidation move hugetlb_bootmem_alloc() to > > mm_core_early_init(). > > > > Signed-off-by: Mike Rapoport (Microsoft) <[email protected]> > I've bisected a problem with virtme-ng testing a NUMA memoryless > node setup (on x86_64) to this patch (commit d49004c5f0c1). > > It's executed like this, where node 0 has memory and node 1 only cpus: > > vng -vr . -p 8 -m 4G --numa 4G,cpus=0-3 --numa 0,cpus=4-7 > > This fails to boot due to: > > [ 0.095894] BUG: unable to handle page fault for address: 0000000000004620 > [ 0.097196] #PF: supervisor read access in kernel mode > [ 0.098180] #PF: error_code(0x0000) - not-present page > [ 0.099155] PGD 0 P4D 0 > [ 0.099641] Oops: Oops: 0000 [#1] SMP NOPTI > [ 0.100437] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted > 6.19.0-rc6-00152-gf206359553c9 #53 PREEMPT > [ 0.102201] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS > rel-1.17.0-2-g4f253b9b-prebuilt.qemu.org 04/01/2014 > [ 0.104313] RIP: 0010:mm_core_init_early+0x263/0x900 > [ 0.105271] Code: 93 ff 72 09 8b 7c 24 30 e8 da 82 00 00 48 63 44 24 30 45 > 31 db 4c 8b 24 c5 a0 7b 1d 9a 48 89 c3 4c 89 5c 24 50 4c 89 5c 24 58 <41> 83 > bc 24 20 46 00 00 00 75 0b 41 83 bc 24 14 47 00 00 00 74 04 > [ 0.108863] RSP: 0000:ffffffff99403e38 EFLAGS: 00010046 > [ 0.109861] RAX: 0000000000000001 RBX: 0000000000000001 RCX: > 0000000000000001 > [ 0.111223] RDX: 0000000000000040 RSI: 0000000000100000 RDI: > ffff89597fffae00 > [ 0.112577] RBP: 0000000000000005 R08: 0000000000000000 R09: > ffff89597fffa200 > [ 0.113924] R10: 80000000ffffe000 R11: 0000000000000000 R12: > 0000000000000000 > [ 0.115294] R13: 0000000000000000 R14: 0000000000000000 R15: > 0000000000000000 > [ 0.116656] FS: 0000000000000000(0000) GS:0000000000000000(0000) > knlGS:0000000000000000 > [ 0.118193] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 0.119283] CR2: 0000000000004620 CR3: 0000000060048000 CR4: > 00000000000000b0 > [ 0.120645] Call Trace: > [ 0.121122] <TASK> > [ 0.121521] start_kernel+0x5d/0x780 > [ 0.122206] x86_64_start_reservations+0x24/0x30 > [ 0.123079] x86_64_start_kernel+0xd1/0xe0 > [ 0.123860] common_startup_64+0x12c/0x138 > [ 0.124641] </TASK> > [ 0.125061] Modules linked in: > [ 0.125646] CR2: 0000000000004620 > [ 0.126279] ---[ end trace 0000000000000000 ]--- > [ 0.127162] RIP: 0010:mm_core_init_early+0x263/0x900 > [ 0.128106] Code: 93 ff 72 09 8b 7c 24 30 e8 da 82 00 00 48 63 44 24 30 45 > 31 db 4c 8b 24 c5 a0 7b 1d 9a 48 89 c3 4c 89 5c 24 50 4c 89 5c 24 58 <41> 83 > bc 24 20 46 00 00 00 75 0b 41 83 bc 24 14 47 00 00 00 74 04 > [ 0.131676] RSP: 0000:ffffffff99403e38 EFLAGS: 00010046 > [ 0.132684] RAX: 0000000000000001 RBX: 0000000000000001 RCX: > 0000000000000001 > [ 0.134033] RDX: 0000000000000040 RSI: 0000000000100000 RDI: > ffff89597fffae00 > [ 0.135412] RBP: 0000000000000005 R08: 0000000000000000 R09: > ffff89597fffa200 > [ 0.136763] R10: 80000000ffffe000 R11: 0000000000000000 R12: > 0000000000000000 > [ 0.138112] R13: 0000000000000000 R14: 0000000000000000 R15: > 0000000000000000 > [ 0.139487] FS: 0000000000000000(0000) GS:0000000000000000(0000) > knlGS:0000000000000000 > [ 0.141014] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 0.142094] CR2: 0000000000004620 CR3: 0000000060048000 CR4: > 00000000000000b0 > [ 0.143448] Kernel panic - not syncing: Attempted to kill the idle task! > [ 0.144833] ---[ end Kernel panic - not syncing: Attempted to kill the > idle task! ]--- > > > ./scripts/faddr2line vmlinux mm_core_init_early+0x263/0x900 > mm_core_init_early+0x263/0x900: > free_area_init_node at mm/mm_init.c:1721 > (inlined by) free_area_init at mm/mm_init.c:1902 > (inlined by) mm_core_init_early at mm/mm_init.c:2681 > > It crashes at WARN_ON(pgdat->nr_zones || pgdat->kswapd_highest_zoneidx); > because pgdat is NULL. > > With some debug printk's I've figured out that in free_area_init() > we have: > > if (!node_online(nid)) > alloc_offline_node_data(nid); > > pgdat = NODE_DATA(nid); > free_area_init_node(nid); > > > But node_online() is true so this allocation doesn't happen, and > pgdat remains NULL. > > And node_online() becomes true in init_cpu_to_node(): > > if (!node_online(node)) > node_set_online(node); > > But without having a pgdat allocated. > > I was able to workaround this by changing the code in free_area_init() to > > if (!node_online(nid) || !NODE_DATA(nid)) > alloc_offline_node_data(nid);
if (!NODE_DATA(nid)) is enough ... > But I don't have the bigger picture, and also didn't check yet what exactly > about this patch results in the failure. Probably ordering of various related > actions. Thoughts? ... and there's a fix already in the mm-hotfixes-stable: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/commit/?h=mm-hotfixes-unstable&id=a4ab97e34bb687a2ca63fc70b47e8762e689797f -- Sincerely yours, Mike.
