Hi, I've enabled nested KVM on my L0 (host) kernel and have created a guest with the CPU model copied from the host. Inside this guest I've installed libvirt and am trying to create a KVM guest (L2 guest). As soon as virt-manager tries to create the domain, the L1 guest reboots and the following WARNING is logged by the L0 kernel: Feb 06 20:35:18 saturn kernel: ------------[ cut here ]------------ Feb 06 20:35:18 saturn kernel: WARNING: CPU: 0 PID: 2352 at arch/x86/kvm/vmx.c:9190 nested_vmx_vmexit+0x7fe/0x890 [kvm_intel]() Feb 06 20:35:18 saturn kernel: Modules linked in: vhost_net vhost macvtap macvlan tun xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat ipt_REJECT nf_reject_ipv4 bridge stp llc bnep bluetooth binfmt_misc cpufreq_userspace cpufreq_powersave cpufreq_conservative cpufreq_stats nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter ip6_tables xt_tcpudp nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack iptable_filter ip_tables x_tables snd_hda_codec_hdmi cx88_blackbird cx2341x cx22702 cx88_dvb cx88_vp3054_i2c videobuf2_dvb dvb_core wm8775 tuner_simple tuner_types iTCO_wdt iTCO_vendor_support tda9887 tda8290 tuner snd_hda_codec_via snd_hda_codec_generic evdev snd_hda_intel cx8800 snd_hda_controller nouveau cx8802 snd_hda_codec videobuf2_dma_sg joydev cx88_alsa coretemp snd_hwdep Feb 06 20:35:18 saturn kernel: videobuf2_memops video mxm_wmi cx88xx wmi videobuf2_core tveeprom rc_core v4l2_common videodev media kvm_intel drm_kms_helper ttm drm snd_pcm arc4 kvm psmouse rt61pci eeprom_93cx6 rt2x00pci rt2x00mmio snd_timer rt2x00lib snd mac80211 cfg80211 i2c_algo_bit i2c_i801 soundcore serio_raw rfkill i7core_edac edac_core 8250_fintek xhci_pci xhci_hcd i2c_core lpc_ich mfd_core asus_atk0110 shpchp button acpi_cpufreq processor thermal_sys loop firewire_sbp2 fuse parport_pc ppdev lp parport autofs4 ext4 crc16 mbcache jbd2 btrfs xor raid6_pq dm_mod raid1 raid0 md_mod sg sr_mod cdrom sd_mod hid_generic usbhid hid usb_storage crc32c_intel firewire_ohci ahci libahci firewire_core crc_itu_t libata scsi_mod ehci_pci ehci_hcd r8169 mii usbcore usb_common Feb 06 20:35:18 saturn kernel: CPU: 0 PID: 2352 Comm: qemu-system-x86 Not tainted 3.19.0-rc7 #1 Feb 06 20:35:18 saturn kernel: Hardware name: System manufacturer System Product Name/P7P55D-E, BIOS 1504 12/14/2010 Feb 06 20:35:18 saturn kernel: 0000000000000000 ffffffffa06f19fa ffffffff815357b8 0000000000000000 Feb 06 20:35:18 saturn kernel: ffffffff8106cde1 ffff8801e4f53000 0000000000000000 0000000000000014 Feb 06 20:35:18 saturn kernel: 0000000000000000 0000000000000000 ffffffffa06de3ce 0000000000000000 Feb 06 20:35:18 saturn kernel: Call Trace: Feb 06 20:35:18 saturn kernel: [<ffffffff815357b8>] ? dump_stack+0x40/0x50 Feb 06 20:35:18 saturn kernel: [<ffffffff8106cde1>] ? warn_slowpath_common+0x81/0xb0 Feb 06 20:35:18 saturn kernel: [<ffffffffa06de3ce>] ? nested_vmx_vmexit+0x7fe/0x890 [kvm_intel] Feb 06 20:35:18 saturn kernel: [<ffffffffa05d370b>] ? kvm_arch_vcpu_ioctl_run+0xd7b/0x1220 [kvm] Feb 06 20:35:18 saturn kernel: [<ffffffffa05cf0cc>] ? kvm_arch_vcpu_load+0x4c/0x1f0 [kvm] Feb 06 20:35:18 saturn kernel: [<ffffffffa05bf982>] ? kvm_vcpu_ioctl+0x322/0x5d0 [kvm] Feb 06 20:35:18 saturn kernel: [<ffffffff8109bdc6>] ? set_next_entity+0x56/0x70 Feb 06 20:35:18 saturn kernel: [<ffffffff810128e0>] ? __switch_to+0x440/0x5e0 Feb 06 20:35:18 saturn kernel: [<ffffffff811cf908>] ? do_vfs_ioctl+0x2e8/0x4f0 Feb 06 20:35:18 saturn kernel: [<ffffffff8110161c>] ? __audit_syscall_entry+0xbc/0x110 Feb 06 20:35:18 saturn kernel: [<ffffffff810228fb>] ? syscall_trace_enter_phase1+0xfb/0x160 Feb 06 20:35:18 saturn kernel: [<ffffffffa05c71a4>] ? kvm_on_user_return+0x44/0x80 [kvm] Feb 06 20:35:18 saturn kernel: [<ffffffff811cfb91>] ? SyS_ioctl+0x81/0xa0 Feb 06 20:35:18 saturn kernel: [<ffffffff8153b4cf>] ? int_signal+0x12/0x17 Feb 06 20:35:18 saturn kernel: [<ffffffff8153b22d>] ? system_call_fastpath+0x16/0x1b Feb 06 20:35:18 saturn kernel: ---[ end trace e7e11898e469021e ]--- I first hit this bug on the Debian 3.16.7-ckt4-3 kernel, but it's the first kernel I tried so the bug might be older. This system has the following processor type: processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 30 model name : Intel(R) Core(TM) i5 CPU 750 @ 2.67GHz stepping : 5 microcode : 0x7 cpu MHz : 1467.000 cache size : 8192 KB physical id : 0 siblings : 4 core id : 0 cpu cores : 4 apicid : 0 initial apicid : 0 fpu : yes fpu_exception : yes cpuid level : 11 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 sse4_2 popcnt lahf_lm ida dtherm tpr_shadow vnmi flexpriority ept vpid bugs : bogomips : 5349.73 clflush size : 64 cache_alignment : 64 address sizes : 36 bits physical, 48 bits virtual power management: rik@saturn:~$ lscpu Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Byte Order: Little Endian CPU(s): 4 On-line CPU(s) list: 0-3 Thread(s) per core: 1 Core(s) per socket: 4 Socket(s): 1 NUMA node(s): 1 Vendor ID: GenuineIntel CPU family: 6 Model: 30 Model name: Intel(R) Core(TM) i5 CPU 750 @ 2.67GHz Stepping: 5 CPU MHz: 1200.000 CPU max MHz: 2668.0000 CPU min MHz: 1200.0000 BogoMIPS: 5349.73 Virtualization: VT-x L1d cache: 32K L1i cache: 32K L2 cache: 256K L3 cache: 8192K NUMA node0 CPU(s): 0-3 Regards, Rik
Fixed with "KVM: nVMX: mask unrestricted_guest if disabled on L0". (https://lkml.org/lkml/2015/3/17/478)