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On 6/12/2025 1:11 PM, Leon Romanovsky wrote: > [ 0.032188] CPU topo: Max. logical packages: 10 > [ 0.032189] CPU topo: Max. logical dies: 10 > [ 0.032189] CPU topo: Max. dies per package: 1 > [ 0.032194] CPU topo: Max. threads per core: 1 > [ 0.032194] CPU topo: Num. cores per package: 1 > [ 0.032195] CPU topo: Num. threads per package: 1 > [ 0.032195] CPU topo: Allowing 10 present CPUs plus 0 hotplug CPUs This indicates each CPU is a socket leading to 10 sockets ... > [ 0.288498] smp: Bringing up secondary CPUs ... > [ 0.289225] smpboot: x86: Booting SMP configuration: > [ 0.289900] .... node #0, CPUs: #1 > [ 0.290511] .... node #1, CPUs: #2 #3 > [ 0.291559] .... node #2, CPUs: #4 #5 > [ 0.292557] .... node #3, CPUs: #6 #7 > [ 0.293593] .... node #4, CPUs: #8 #9 > [ 0.326310] smp: Brought up 5 nodes, 10 CPUs ... and this indicates two sockets are grouped as one NUMA node leading to 5 nodes in total. I tried the following: qemu-system-x86_64 -enable-kvm \ -cpu EPYC-Milan-v2 -m 20G -smp cpus=10,sockets=10 \ -machine q35 \ -object memory-backend-ram,size=4G,id=m0 \ -object memory-backend-ram,size=4G,id=m1 \ -object memory-backend-ram,size=4G,id=m2 \ -object memory-backend-ram,size=4G,id=m3 \ -object memory-backend-ram,size=4G,id=m4 \ -numa node,cpus=0-1,memdev=m0,nodeid=0 \ -numa node,cpus=2-3,memdev=m1,nodeid=1 \ -numa node,cpus=4-5,memdev=m2,nodeid=2 \ -numa node,cpus=6-7,memdev=m3,nodeid=3 \ -numa node,cpus=8-9,memdev=m4,nodeid=4 \ ... but could not hit this issue with v6.16-rc1 kernel and QEMU emulator version 10.0.50 (v10.0.0-1610-gd9ce74873a) > [ 0.327532] smpboot: Total of 10 processors activated (51878.08 BogoMIPS) > [ 0.329252] ------------[ cut here ]------------ > [ 0.329252] WARNING: CPU: 0 PID: 1 at kernel/sched/topology.c:2486 build_sched_domains+0xe67/0x13a0 > [ 0.330608] Modules linked in: > [ 0.331050] CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.16.0-rc1_for_upstream_min_debug_2025_06_09_14_44 #1 NONE > [ 0.332386] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 > [ 0.333767] RIP: 0010:build_sched_domains+0xe67/0x13a0 > [ 0.334298] Code: ff ff 8b 6c 24 08 48 8b 44 24 68 65 48 2b 05 60 24 d0 01 0f 85 03 05 00 00 48 83 c4 70 89 e8 5b 5d 41 5c 41 5d 41 5e 41 5f c3 <0f> 0b e9 65 fe ff ff 48 c7 c7 28 fb 08 82 4c 89 44 24 28 c6 05 e4 > [ 0.336635] RSP: 0000:ffff8881002efe30 EFLAGS: 00010202 > [ 0.337326] RAX: 00000000ffffff01 RBX: 0000000000000002 RCX: 00000000ffffff01 > [ 0.338234] RDX: 00000000fffffff6 RSI: 0000000000000300 RDI: ffff888100047168 > [ 0.338523] RBP: 0000000000000000 R08: ffff888100047168 R09: 0000000000000000 > [ 0.339425] R10: ffffffff830dee80 R11: 0000000000000000 R12: ffff888100047168 > [ 0.340323] R13: 0000000000000002 R14: ffff888100193480 R15: ffff888380030f40 > [ 0.341221] FS: 0000000000000000(0000) GS:ffff8881b9b76000(0000) knlGS:0000000000000000 > [ 0.342298] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 0.343096] CR2: ffff88843ffff000 CR3: 000000000282c001 CR4: 0000000000370eb0 > [ 0.344042] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 0.344927] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [ 0.345811] Call Trace: > [ 0.346191] > [ 0.346429] sched_init_smp+0x32/0xa0 > [ 0.346944] ? stop_machine+0x2c/0x40 > [ 0.347460] kernel_init_freeable+0xf5/0x260 > [ 0.348031] ? rest_init+0xc0/0xc0 > [ 0.348513] kernel_init+0x16/0x120 > [ 0.349008] ret_from_fork+0x5e/0xd0 > [ 0.349510] ? rest_init+0xc0/0xc0 > [ 0.349998] ret_from_fork_asm+0x11/0x20 > [ 0.350464] > [ 0.350812] ---[ end trace 0000000000000000 ]--- Ah! Since this happens so early topology isn't created yet for the debug prints to hit! Is it possible to get a dmesg with "ignore_loglevel" and "sched_verbose" on an older kernel that did not throw this error on the same host? > >> >> Even the qemu cmdline for the guest can help! We can try reproducing >> it at our end then. Thank you for all the help. > > It is custom QEMU with limited access to hypervisor. This crash is > inside VM. Noted! Thank a ton for all the data provided. -- Thanks and Regards, Prateek