https://bugzilla.kernel.org/show_bug.cgi?id=218684 Bug ID: 218684 Summary: CPU soft lockups in KVM VMs on kernel 6.x after switching hypervisor from C8S to C9S Product: Virtualization Version: unspecified Hardware: Intel OS: Linux Status: NEW Severity: normal Priority: P3 Component: kvm Assignee: virtualization_kvm@xxxxxxxxxxxxxxxxxxxx Reporter: frantisek@xxxxxxxxx Regression: No Hey! I'm currently in the middle of moving some of our hypervisors for upstream systemd CI from CentOS Stream 8 to CentOS Stream 9 (as the former will go EOL soon), and started hitting soft lockups on the guest machines (Arch Linux, both with "stock" kernel and mainline one). The hypervisors are AWS EC2 C5n Metal instances [0] running CentOS Stream, which then run Arch Linux (KVM) VMs (using libvirt via Vagrant) - cpuinfo from one of the guests is at [1]. The "production" hypervisors currently run CentOS Stream 8 (kernel 4.18.0-548.el8.x86_64) and everything is fine. However, after trying to upgrade a couple of them to CentOS Stream 9 (kernel 5.14.0-432.el9.x86_64) the guests started exhibiting frequent soft lockups when running just the systemd unit test suite. I played around with the kernel version inside the guest and it doesn't seem to make a difference - I could reproduce the issue with kernels 6.6.24-1 (linux-lts), 6.8.2.arch2-1 (linux), and 6.9.0-rc2-1-mainline (linux-mainline). One example with the mainline kernel on the guest: [ 58.800435] (sh)[5787]: Found cgroup2 on /sys/fs/cgroup/, full unified hierarchy [ 58.800578] (sh)[5787]: Found cgroup2 on /sys/fs/cgroup/, full unified hierarchy [ 75.709475] kernel: watchdog: BUG: soft lockup - CPU#30 stuck for 16s! [swapper/30:0] [ 75.728228] kernel: Modules linked in: dummy rpcsec_gss_krb5 auth_rpcgss nfsv4 dns_resolver nfs lockd grace sunrpc netfs snd_seq_dummy snd_hrtimer snd_seq snd_seq_device snd_timer snd soundcore intel_rapl_msr intel_rapl_common intel_uncore_frequency_common isst_if_common nfit libnvdimm 8021q garp mrp stp llc cbc encrypted_keys trusted asn1_encoder tee vfat fat kvm_intel kvm crct10dif_pclmul crc32_pclmul polyval_clmulni polyval_generic gf128mul ghash_clmulni_intel sha512_ssse3 sha1_ssse3 aesni_intel crypto_simd cryptd rapl cfg80211 rfkill iTCO_wdt joydev intel_pmc_bxt mousedev iTCO_vendor_support i2c_i801 psmouse i2c_smbus pcspkr lpc_ich mac_hid fuse loop dm_mod nfnetlink vsock_loopback vmw_vsock_virtio_transport_common vmw_vsock_vmci_transport vsock vmw_vmci qemu_fw_cfg ip_tables x_tables btrfs blake2b_generic libcrc32c crc32c_generic xor raid6_pq serio_raw atkbd virtio_net libps2 net_failover virtio_blk failover vivaldi_fmap virtio_balloon virtio_rng virtio_pci crc32c_intel intel_agp sha256_ssse3 virtio_pci_legacy_dev i8042 [ 75.796349] kernel: xhci_pci intel_gtt virtio_pci_modern_dev xhci_pci_renesas cirrus serio [ 75.796396] kernel: CPU: 30 PID: 0 Comm: swapper/30 Not tainted 6.9.0-rc2-1-mainline #1 4c361158dea5838a7441c4025165296045a48154 [ 75.796413] kernel: Hardware name: Red Hat KVM/RHEL, BIOS edk2-20240214-1.el9 02/14/2024 [ 75.796414] kernel: RIP: 0010:pv_native_safe_halt+0xf/0x20 [ 75.796421] kernel: Code: 22 d7 c3 cc cc cc cc 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 23 db 24 00 fb f4 <c3> cc cc cc cc 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 [ 75.796423] kernel: RSP: 0018:ffffa945c01b7ed8 EFLAGS: 00000246 [ 75.796428] kernel: RAX: 000000000000001e RBX: ffff921dc0b33000 RCX: ffff921de2bf2908 [ 75.796431] kernel: RDX: 000000000000001e RSI: 000000000000001e RDI: 00000000001737f4 [ 75.796433] kernel: RBP: 000000000000001e R08: 0000000000000001 R09: 0000000000000000 [ 75.796434] kernel: R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000 [ 75.796436] kernel: R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 75.796437] kernel: FS: 0000000000000000(0000) GS:ffff923cbe900000(0000) knlGS:0000000000000000 [ 75.796439] kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 75.796441] kernel: CR2: 00007f08c013e000 CR3: 000000186ac20002 CR4: 0000000000770ef0 [ 75.796444] kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 75.796445] kernel: DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 75.796446] kernel: PKRU: 55555554 [ 75.796447] kernel: Call Trace: [ 75.796450] kernel: <IRQ> [ 75.800549] kernel: ? watchdog_timer_fn+0x1dd/0x260 [ 75.800553] kernel: ? __pfx_watchdog_timer_fn+0x10/0x10 [ 75.800556] kernel: ? __hrtimer_run_queues+0x10f/0x2a0 [ 75.800560] kernel: ? hrtimer_interrupt+0xfa/0x230 [ 75.800563] kernel: ? __sysvec_apic_timer_interrupt+0x55/0x150 [ 75.800567] kernel: ? sysvec_apic_timer_interrupt+0x6c/0x90 [ 75.800569] kernel: </IRQ> [ 75.800569] kernel: <TASK> [ 75.800571] kernel: ? asm_sysvec_apic_timer_interrupt+0x1a/0x20 [ 75.800590] kernel: ? pv_native_safe_halt+0xf/0x20 [ 75.800593] kernel: default_idle+0x9/0x20 [ 75.800596] kernel: default_idle_call+0x30/0x100 [ 75.800598] kernel: do_idle+0x1cb/0x210 [ 75.800603] kernel: cpu_startup_entry+0x29/0x30 [ 75.800606] kernel: start_secondary+0x11c/0x140 [ 75.800610] kernel: common_startup_64+0x13e/0x141 [ 75.800616] kernel: </TASK> [ 75.800619] kernel: watchdog: BUG: soft lockup - CPU#59 stuck for 16s! [swapper/59:0] [ 75.802944] kernel: Modules linked in: dummy rpcsec_gss_krb5 auth_rpcgss nfsv4 dns_resolver nfs lockd grace sunrpc netfs snd_seq_dummy snd_hrtimer snd_seq snd_seq_device snd_timer snd soundcore intel_rapl_msr intel_rapl_common intel_uncore_frequency_common isst_if_common nfit libnvdimm 8021q garp mrp stp llc cbc encrypted_keys trusted asn1_encoder tee vfat fat kvm_intel kvm crct10dif_pclmul crc32_pclmul polyval_clmulni polyval_generic gf128mul ghash_clmulni_intel sha512_ssse3 sha1_ssse3 aesni_intel crypto_simd cryptd rapl cfg80211 rfkill iTCO_wdt joydev intel_pmc_bxt mousedev iTCO_vendor_support i2c_i801 psmouse i2c_smbus pcspkr lpc_ich mac_hid fuse loop dm_mod nfnetlink vsock_loopback vmw_vsock_virtio_transport_common vmw_vsock_vmci_transport vsock vmw_vmci qemu_fw_cfg ip_tables x_tables btrfs blake2b_generic libcrc32c crc32c_generic xor raid6_pq serio_raw atkbd virtio_net libps2 net_failover virtio_blk failover vivaldi_fmap virtio_balloon virtio_rng virtio_pci crc32c_intel intel_agp sha256_ssse3 virtio_pci_legacy_dev i8042 [ 75.803034] kernel: xhci_pci intel_gtt virtio_pci_modern_dev xhci_pci_renesas cirrus serio [ 75.803043] kernel: CPU: 59 PID: 0 Comm: swapper/59 Tainted: G L 6.9.0-rc2-1-mainline #1 4c361158dea5838a7441c4025165296045a48154 [ 75.803048] kernel: Hardware name: Red Hat KVM/RHEL, BIOS edk2-20240214-1.el9 02/14/2024 [ 75.803050] kernel: RIP: 0010:pv_native_safe_halt+0xf/0x20 [ 75.803057] kernel: Code: 22 d7 c3 cc cc cc cc 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 23 db 24 00 fb f4 <c3> cc cc cc cc 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 [ 75.803059] kernel: RSP: 0018:ffffa945c029fed8 EFLAGS: 00000252 [ 75.803062] kernel: RAX: 000000000000003b RBX: ffff921dc0c78000 RCX: ffff921e01edf5a8 [ 75.803064] kernel: RDX: 000000000000003b RSI: 000000000000003b RDI: 0000000000121a9c [ 75.803065] kernel: RBP: 000000000000003b R08: 0000000000000001 R09: 0000000000000000 [ 75.803067] kernel: R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000 [ 75.803069] kernel: R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 75.803070] kernel: FS: 0000000000000000(0000) GS:ffff923cbf780000(0000) knlGS:0000000000000000 [ 75.803072] kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 75.803074] kernel: CR2: 00007f08c013e000 CR3: 000000186ac20005 CR4: 0000000000770ef0 [ 75.803078] kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 75.803079] kernel: DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 75.803081] kernel: PKRU: 55555554 [ 75.803082] kernel: Call Trace: [ 75.803085] kernel: <IRQ> [ 75.803091] kernel: ? watchdog_timer_fn+0x1dd/0x260 [ 75.803096] kernel: ? __pfx_watchdog_timer_fn+0x10/0x10 [ 75.803098] kernel: ? __hrtimer_run_queues+0x10f/0x2a0 [ 75.803103] kernel: ? hrtimer_interrupt+0xfa/0x230 [ 75.803106] kernel: ? __sysvec_apic_timer_interrupt+0x55/0x150 [ 75.803111] kernel: ? sysvec_apic_timer_interrupt+0x6c/0x90 [ 75.803113] kernel: </IRQ> [ 75.803114] kernel: <TASK> [ 75.803116] kernel: ? asm_sysvec_apic_timer_interrupt+0x1a/0x20 [ 75.803122] kernel: ? pv_native_safe_halt+0xf/0x20 [ 75.803125] kernel: default_idle+0x9/0x20 [ 75.803129] kernel: default_idle_call+0x30/0x100 [ 75.803131] kernel: do_idle+0x1cb/0x210 [ 75.803137] kernel: cpu_startup_entry+0x29/0x30 [ 75.803139] kernel: start_secondary+0x11c/0x140 [ 75.803145] kernel: common_startup_64+0x13e/0x141 [ 75.803151] kernel: </TASK> ... The full stack trace is quite long, please see [2] which is a complete journal from the machine boot. I can reproduce the soft lockups quite reliably. However, I'm not really sure who to blame here, since there's too many moving parts. But my first question would be - is this an issue of the guest (Arch Linux) kernel, or is it/can it be caused by the host kernel? I did some testing and if I use the _same_ image on the C8S hypervisor (with all three guest kernel variations), the issue disappears, but I'm still not convinced that this might be the host kernel doings. I'm more than happy to debug this further, but currently I have no idea where to start, so any hint would be greatly appreciated. [0] https://aws.amazon.com/ec2/instance-types/c5/ [1] https://mrc0mmand.fedorapeople.org/kernel_kvm_softlockup/arch-mainline-cpuinfo.log [2] https://mrc0mmand.fedorapeople.org/kernel_kvm_softlockup/arch-mainline-journal.log -- You may reply to this email to add a comment. 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