Hi all, it seems the "new" KVM_SET_NESTED_STATE interface has some remaining robustness issues. The most urgent one: With the help of latest QEMU master that uses this interface, you can easily crash the host. You just need to start qemu-system-x86 -enable-kvm in L1 and then hard-reset L1. The host CPU that ran this will stall, the system will freeze soon. I've also seen a pattern with my Jailhouse test VM where I seems to get stuck in a loop between L1 and L2: qemu-system-x86-6660 [007] 398.691401: kvm_nested_vmexit: rip 7fa9ee5224e4 reason IO_INSTRUCTION info1 5658000b info2 0 int_info 0 int_info_err 0 qemu-system-x86-6660 [007] 398.691402: kvm_fpu: unload qemu-system-x86-6660 [007] 398.691403: kvm_userspace_exit: reason KVM_EXIT_IO (2) qemu-system-x86-6660 [007] 398.691440: kvm_fpu: load qemu-system-x86-6660 [007] 398.691441: kvm_pio: pio_read at 0x5658 size 4 count 1 val 0x4 qemu-system-x86-6660 [007] 398.691443: kvm_mmu_get_page: existing sp gfn 3a22e 1/4 q3 direct --x !pge !nxe root 6 sync qemu-system-x86-6660 [007] 398.691444: kvm_entry: vcpu 3 qemu-system-x86-6660 [007] 398.691475: kvm_exit: reason IO_INSTRUCTION rip 0x7fa9ee5224e4 info 5658000b 0 qemu-system-x86-6660 [007] 398.691476: kvm_nested_vmexit: rip 7fa9ee5224e4 reason IO_INSTRUCTION info1 5658000b info2 0 int_info 0 int_info_err 0 qemu-system-x86-6660 [007] 398.691477: kvm_fpu: unload qemu-system-x86-6660 [007] 398.691478: kvm_userspace_exit: reason KVM_EXIT_IO (2) qemu-system-x86-6660 [007] 398.691526: kvm_fpu: load qemu-system-x86-6660 [007] 398.691527: kvm_pio: pio_read at 0x5658 size 4 count 1 val 0x4 qemu-system-x86-6660 [007] 398.691529: kvm_mmu_get_page: existing sp gfn 3a22e 1/4 q3 direct --x !pge !nxe root 6 sync qemu-system-x86-6660 [007] 398.691530: kvm_entry: vcpu 3 qemu-system-x86-6660 [007] 398.691533: kvm_exit: reason IO_INSTRUCTION rip 0x7fa9ee5224e4 info 5658000b 0 qemu-system-x86-6660 [007] 398.691534: kvm_nested_vmexit: rip 7fa9ee5224e4 reason IO_INSTRUCTION info1 5658000b info2 0 int_info 0 int_info_err 0 These issues disappear when going from ebbfef2f back to 6cfd7639 (both with build fixes) in QEMU. Host kernels tested: 5.1.16 (distro) and 5.2 (vanilla). Jan -- Siemens AG, Corporate Technology, CT RDA IOT SES-DE Corporate Competence Center Embedded Linux
