Hi Marcelo, This issue can also been seen on the latest Ubuntu 18.04 image. It is also seen in the 5.10-rc7 Linux kernel as well as 5.4. The issue can be reproduced 100% of the time using a more simple setup as described below. A basic "hello world" C program compiled for 32 bit crashes the Azure Linux host if a standard VM is first started as described below using qemu-kvm. // the Azure host kernel panic reproduction with 32 bit hello world. Includes the kernel panic traceback at the end. // Install a standard ubuntu image on the host like below (if the 11/25/20 is no longer available, the current one will do). root@jnpronevm1:~# wget https://cloud-images.ubuntu.com/bionic/20201125/bionic-server-cloudimg-amd64.img --2020-11-30 19:43:20--  https://cloud-images.ubuntu.com/bionic/20201125/bionic-server-cloudimg-amd64.img Resolving cloud-images.ubuntu.com (cloud-images.ubuntu.com)... 91.189.88.247, 91.189.88.248, 2001:67c:1360:8001::33, ... Connecting to cloud-images.ubuntu.com (cloud-images.ubuntu.com)|91.189.88.247|:443... connected. HTTP request sent, awaiting response... 200 OK Length: 360775680 (344M) [application/octet-stream] Saving to: ‘bionic-server-cloudimg-amd64.img.1’ bionic-server-cloudim 100%[======================>] 344.06M  20.4MB/s    in 18s      2020-11-30 19:43:39 (19.2 MB/s) - ‘bionic-server-cloudimg-amd64.img.1’ saved [360775680/360775680] // make sure qemu-kvm is installed and kvm acceleration can be used. root@jnpronevm1:~# root@jnpronevm1:~# kvm-ok INFO: /dev/kvm exists KVM acceleration can be used root@jnpronevm1:~# cat hello.c #include int main() {     printf("Hello world\n");      } // compile about in 32 bit mode, 64 bit does not show the issue root@jnpronevm1:~# gcc -m32 hello.c -o hello // start the VM from the above downloaded image. root@jnpronevm1:~#/usr/bin/qemu-system-x86_64 -daemonize -name u1 -machine pc-i440fx-bionic,accel=kvm -m 1024 -smp 2,sockets=1 -uuid 772495e6-8658-4306-ba5f-f59c15f42f69 -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -drive file=bionic-server-cloudimg-amd64.img,if=none,id=drive-virtio-disk0,format=raw,cache=writeback -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x7,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -chardev socket,id=charserial0,host=127.0.0.1,port=8601,telnet,server,nowait,logfile=/var/log/console.log -vnc 127.0.0.1:0 -vga cirrus qemu-system-x86_64: warning: host doesn't support requested feature: CPUID.80000001H:ECX.svm [bit 2] qemu-system-x86_64: warning: host doesn't support requested feature: CPUID.80000001H:ECX.svm [bit 2] root@jnpronevm1:~# ps aux | grep qemu root      2966 45.6  0.1 1655976 41064 ?       Sl   20:02   0:02 /usr/bin/qemu-system-x86_64 -daemonize -name u1 -machine pc-i440fx-bionic,accel=kvm -m 1024 -smp 2,sockets=1 -uuid 772495e6-8658-4306-ba5f-f59c15f42f69 -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -drive file=bionic-server-cloudimg-amd64.img,if=none,id=drive-virtio-disk0,format=raw,cache=writeback -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x7,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -chardev socket,id=charserial0,host=127.0.0.1,port=8601,telnet,server,nowait,logfile=/var/log/console.log -vnc 127.0.0.1:0 -vga cirrus root      2979  0.0  0.0  14864  1064 pts/0    S+   20:02   0:00 grep qemu root@jnpronevm1:~# ./hello The host VM hung up due to kernel panic after above step. ### the host vm hit kernel panic after running hello program. [ 7858.522920] PANIC: double fault, error_code: 0x0 [ 7858.525679] Kernel panic - not syncing: Machine halted. [ 7858.525679] CPU: 5 PID: 4746 Comm: hello Not tainted 4.15.18+test #1 [ 7858.525679] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS 090008  12/07/2018 [ 7858.525679] Call Trace: [ 7858.525679]  <#DF> [ 7858.525679]  dump_stack+0x63/0x8b [ 7858.525679]  panic+0xe4/0x244 [ 7858.525679]  df_debug+0x2d/0x30 [ 7858.525679]  do_double_fault+0x9a/0x130 [ 7858.525679]  double_fault+0x1e/0x30 [ 7858.525679] RIP: 0010:0x1a80 [ 7858.525679] RSP: 0018:000000000000e200 EFLAGS: 00010086 [ 7858.525679] RAX: 00000000000000c5 RBX: 0000000000000001 RCX: 00000000ffc98f2c [ 7858.525679] RDX: 00000000000007d4 RSI: 00000000f7ef2d80 RDI: 00000000f7ef2000 [ 7858.525679] RBP: 00000000ffc98ed8 R08: 0000000000000000 R09: 0000000000000000 [ 7858.525679] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 [ 7858.525679] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 7858.525679]  [ 7858.525679] Kernel Offset: 0xf000000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff) [ 7858.525679] ---[ end Kernel panic - not syncing: Machine halted. [ 7858.525679] WARNING: CPU: 5 PID: 4746 at kernel/sched/core.c:1192 set_task_cpu+0x162/0x170 [ 7858.525679] Modules linked in: xt_owner iptable_security nf_conntrack_netlink nfnetlink xfrm_user xfrm_algo xt_addrtype xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat br_netfilter xt_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp bridge stp llc ebtable_filter ebtables aufs ip6table_filter ip6_tables iptable_filter overlay openvswitch nsh nf_conntrack_ipv6 nf_nat_ipv6 nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_defrag_ipv6 nf_nat nf_conntrack nls_iso8859_1 mlx4_en sb_edac mlx4_core devlink kvm_intel kvm irqbypass input_leds joydev mac_hid intel_rapl_perf hv_balloon pci_hyperv serio_raw sch_fq_codel ib_iser rdma_cm iw_cm ib_cm ib_core iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi ip_tables x_tables autofs4 btrfs zstd_compress raid10 raid456 async_raid6_recov [ 7858.525679]  async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear hid_generic crct10dif_pclmul crc32_pclmul ghash_clmulni_intel pcbc hid_hyperv aesni_intel hv_utils hv_storvsc ptp hid hyperv_keyboard scsi_transport_fc hv_netvsc pps_core aes_x86_64 hyperv_fb crypto_simd glue_helper cryptd psmouse pata_acpi i2c_piix4 floppy hv_vmbus [ 7858.525679] CPU: 5 PID: 4746 Comm: hello Not tainted 4.15.18+test #1 [ 7858.525679] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS 090008  12/07/2018 [ 7858.525679] RIP: 0010:set_task_cpu+0x162/0x170 [ 7858.525679] RSP: 0018:ffff960e7fd43ca0 EFLAGS: 00010046 [ 7858.525679] RAX: 0000000000000200 RBX: ffff960e55de16c0 RCX: 0000000000000001 [ 7858.525679] RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff960e55de16c0 [ 7858.525679] RBP: ffff960e7fd43cc0 R08: 0000000000000000 R09: 00000000000000ff [ 7858.525679] R10: 0000000000000000 R11: 0000000000000010 R12: ffff960e55de21ec [ 7858.525679] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000022880 [ 7858.525679] FS:  0000000000000000(0000) GS:ffff960e7fd40000(0063) knlGS:00000000f7f040c0 [ 7858.525679] CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033 [ 7858.525679] CR2: 000000000000e1f8 CR3: 000000086b978002 CR4: 00000000003626e0 [ 7858.525679] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 7858.525679] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 7858.525679] Call Trace: [ 7858.525679]  [ 7858.525679]  try_to_wake_up+0x14f/0x4a0 [ 7858.525679]  default_wake_function+0x12/0x20 [ 7858.525679]  autoremove_wake_function+0x12/0x40 [ 7858.525679]  __wake_up_common+0x8c/0x130 [ 7858.525679]  __wake_up_common_lock+0x80/0xc0 [ 7858.525679]  __wake_up+0x13/0x20 [ 7858.525679]  wake_up_klogd_work_func+0x40/0x60 [ 7858.525679]  irq_work_run_list+0x55/0x80 [ 7858.525679]  ? tick_sched_do_timer+0x40/0x40 [ 7858.525679]  irq_work_tick+0x40/0x50 [ 7858.525679]  update_process_times+0x42/0x60 [ 7858.525679]  tick_sched_handle+0x2a/0x60 [ 7858.525679]  tick_sched_timer+0x39/0x80 [ 7858.525679]  __hrtimer_run_queues+0xe7/0x230 [ 7858.525679]  hrtimer_interrupt+0xb1/0x200 [ 7858.525679]  vmbus_isr+0x16c/0x2a0 [hv_vmbus] [ 7858.525679]  hyperv_vector_handler+0x3f/0x6e [ 7858.525679]  hyperv_callback_vector+0x84/0x90 [ 7858.525679]  [ 7858.525679]  <#DF> [ 7858.525679] RIP: 0010:panic+0x1fe/0x244 [ 7858.525679] RSP: 0018:fffffe00000e3e90 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff0c [ 7858.525679] RAX: 0000000000000034 RBX: fffffe00000e3f00 RCX: 0000000000000006 [ 7858.525679] RDX: 0000000000000000 RSI: 0000000000000096 RDI: ffff960e7fd56490 [ 7858.525679] RBP: fffffe00000e3f08 R08: 0000000000000000 R09: 0000000000000268 [ 7858.525679] R10: 0000000000000000 R11: 0000000000000038 R12: 0000000000000000 [ 7858.525679] R13: 0000000000000000 R14: 000000086b979802 R15: 0000000000000000 [ 7858.525679]  df_debug+0x2d/0x30 [ 7858.525679]  do_double_fault+0x9a/0x130 [ 7858.525679]  double_fault+0x1e/0x30 [ 7858.525679] RIP: 0010:0x1a80 [ 7858.525679] RSP: 0018:000000000000e200 EFLAGS: 00010086 [ 7858.525679] RAX: 00000000000000c5 RBX: 0000000000000001 RCX: 00000000ffc98f2c [ 7858.525679] RDX: 00000000000007d4 RSI: 00000000f7ef2d80 RDI: 00000000f7ef2000 [ 7858.525679] RBP: 00000000ffc98ed8 R08: 0000000000000000 R09: 0000000000000000 [ 7858.525679] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 [ 7858.525679] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 7858.525679]  [ 7858.525679] Code: 2d ff ff ff 80 8b 64 08 00 00 04 e9 49 ff ff ff 0f 0b e9 e8 fe ff ff f7 43 5c fd ff ff ff 0f 84 f2 fe ff ff 0f 0b e9 eb fe ff ff <0f> 0b e9 fa fe ff ff 0f 1f 80 00 00 00 00 0f 1f 44 00 00 55 48 [ 7858.525679] ---[ end trace 21e7449a655e2326 ]--- [ 7858.652373] ------------[ cut here ]------------ [ 7858.652373] sched: Unexpected reschedule of offline CPU#0! [ 7858.652373] WARNING: CPU: 5 PID: 4746 at arch/x86/kernel/smp.c:128 native_smp_send_reschedule+0x3f/0x50 [ 7858.652373] Modules linked in: xt_owner iptable_security nf_conntrack_netlink nfnetlink xfrm_user xfrm_algo xt_addrtype xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat br_netfilter xt_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp bridge stp llc ebtable_filter ebtables aufs ip6table_filter ip6_tables iptable_filter overlay openvswitch nsh nf_conntrack_ipv6 nf_nat_ipv6 nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_defrag_ipv6 nf_nat nf_conntrack nls_iso8859_1 mlx4_en sb_edac mlx4_core devlink kvm_intel kvm irqbypass input_leds joydev mac_hid intel_rapl_perf hv_balloon pci_hyperv serio_raw sch_fq_codel ib_iser rdma_cm iw_cm ib_cm ib_core iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi ip_tables x_tables autofs4 btrfs zstd_compress raid10 raid456 async_raid6_recov [ 7858.652373]  async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear hid_generic crct10dif_pclmul crc32_pclmul ghash_clmulni_intel pcbc hid_hyperv aesni_intel hv_utils hv_storvsc ptp hid hyperv_keyboard scsi_transport_fc hv_netvsc pps_core aes_x86_64 hyperv_fb crypto_simd glue_helper cryptd psmouse pata_acpi i2c_piix4 floppy hv_vmbus [ 7858.652373] CPU: 5 PID: 4746 Comm: hello Tainted: G        W        4.15.18+test #1 [ 7858.652373] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS 090008  12/07/2018 [ 7858.652373] RIP: 0010:native_smp_send_reschedule+0x3f/0x50 [ 7858.652373] RSP: 0018:ffff960e7fd43c28 EFLAGS: 00010086 [ 7858.652373] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000006 [ 7858.652373] RDX: 0000000000000007 RSI: 0000000000000086 RDI: ffff960e7fd56490 [ 7858.652373] RBP: ffff960e7fd43c28 R08: 0000000000000000 R09: 00000000000002a5 [ 7858.652373] R10: 0000000000100000 R11: 0000000000000038 R12: ffff960e55de16c0 [ 7858.652373] R13: ffff960e7fc22880 R14: ffff960e7fd43ce0 R15: ffff960e7fc22880 [ 7858.652373] FS:  0000000000000000(0000) GS:ffff960e7fd40000(0063) knlGS:00000000f7f040c0 [ 7858.652373] CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033 [ 7858.652373] CR2: 000000000000e1f8 CR3: 000000086b978002 CR4: 00000000003626e0 [ 7858.652373] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 7858.652373] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 7858.652373] Call Trace: [ 7858.652373]  [ 7858.652373]  resched_curr+0x6c/0xd0 [ 7858.652373]  check_preempt_curr+0x54/0x90 [ 7858.652373]  ttwu_do_wakeup+0x1e/0x150 [ 7858.652373]  ttwu_do_activate+0x77/0x80 [ 7858.652373]  try_to_wake_up+0x1cc/0x4a0 [ 7858.652373]  default_wake_function+0x12/0x20 [ 7858.652373]  autoremove_wake_function+0x12/0x40 [ 7858.652373]  __wake_up_common+0x8c/0x130 [ 7858.652373]  __wake_up_common_lock+0x80/0xc0 [ 7858.652373]  __wake_up+0x13/0x20 [ 7858.652373]  wake_up_klogd_work_func+0x40/0x60 [ 7858.652373]  irq_work_run_list+0x55/0x80 [ 7858.652373]  ? tick_sched_do_timer+0x40/0x40 [ 7858.652373]  irq_work_tick+0x40/0x50 [ 7858.652373]  update_process_times+0x42/0x60 [ 7858.652373]  tick_sched_handle+0x2a/0x60 [ 7858.652373]  tick_sched_timer+0x39/0x80 [ 7858.652373]  __hrtimer_run_queues+0xe7/0x230 [ 7858.652373]  hrtimer_interrupt+0xb1/0x200 [ 7858.652373]  vmbus_isr+0x16c/0x2a0 [hv_vmbus] [ 7858.652373]  hyperv_vector_handler+0x3f/0x6e [ 7858.652373]  hyperv_callback_vector+0x84/0x90 [ 7858.652373]  [ 7858.652373]  <#DF> [ 7858.652373] RIP: 0010:panic+0x1fe/0x244 [ 7858.652373] RSP: 0018:fffffe00000e3e90 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff0c [ 7858.652373] RAX: 0000000000000034 RBX: fffffe00000e3f00 RCX: 0000000000000006 [ 7858.652373] RDX: 0000000000000000 RSI: 0000000000000096 RDI: ffff960e7fd56490 [ 7858.652373] RBP: fffffe00000e3f08 R08: 0000000000000000 R09: 0000000000000268 [ 7858.652373] R10: 0000000000000000 R11: 0000000000000038 R12: 0000000000000000 [ 7858.652373] R13: 0000000000000000 R14: 000000086b979802 R15: 0000000000000000 [ 7858.652373]  df_debug+0x2d/0x30 [ 7858.652373]  do_double_fault+0x9a/0x130 [ 7858.652373]  double_fault+0x1e/0x30 [ 7858.652373] RIP: 0010:0x1a80 [ 7858.652373] RSP: 0018:000000000000e200 EFLAGS: 00010086 [ 7858.652373] RAX: 00000000000000c5 RBX: 0000000000000001 RCX: 00000000ffc98f2c [ 7858.652373] RDX: 00000000000007d4 RSI: 00000000f7ef2d80 RDI: 00000000f7ef2000 [ 7858.652373] RBP: 00000000ffc98ed8 R08: 0000000000000000 R09: 0000000000000000 [ 7858.652373] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 [ 7858.652373] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 7858.652373]  [ 7858.652373] Code: 92 c0 84 c0 74 17 48 8b 05 7f 71 15 01 be fd 00 00 00 48 8b 40 30 e8 31 b6 ba 00 5d c3 89 fe 48 c7 c7 10 e3 0b 91 e8 b1 49 03 00 <0f> 0b 5d c3 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 [ 7858.652373] ---[ end trace 21e7449a655e2327 ]--- [ 7867.526414] hyperv_fb: Unable to send packet via vmbus [ 7867.526415] hyperv_fb: Unable to send packet via vmbus [ 7867.526415] hyperv_fb: Unable to send packet via vmbus [ 7867.526416] hyperv_fb: Unable to send packet via vmbus [ 7867.526416] hyperv_fb: Unable to send packet via vmbus [ 7867.526417] hyperv_fb: Unable to send packet via vmbus [ 7867.526417] hyperv_fb: Unable to send packet via vmbus [ 7867.526417] hyperv_fb: Unable to send packet via vmbus [ 7867.526418] hyperv_fb: Unable to send packet via vmbus On Thursday, December 10, 2020, 1:50:48 PM PST, Marcelo Cerri