> This program still triggers the warning in kvm_apic_accept_events with > the patch applied (on top of > 093b995e3b55a0ae0670226ddfcb05bfbf0099ae): > > https://gist.githubusercontent.com/dvyukov/2a39303347aa417aea2afd9fd99b7086/raw/09693aa7ed78d22b23948c726767f540b2276a99/gistfile1.txt > > ------------[ cut here ]------------ > WARNING: CPU: 3 PID: 2964 at arch/x86/kvm/lapic.c:2461 > kvm_apic_accept_events+0x46c/0x550 arch/x86/kvm/lapic.c:2461 > CPU: 3 PID: 2964 Comm: a.out Not tainted 4.11.0-rc3+ #365 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:16 [inline] > dump_stack+0x1b8/0x28d lib/dump_stack.c:52 > panic+0x20c/0x423 kernel/panic.c:180 > __warn+0x1c4/0x1e0 kernel/panic.c:541 > warn_slowpath_null+0x2c/0x40 kernel/panic.c:584 > kvm_apic_accept_events+0x46c/0x550 arch/x86/kvm/lapic.c:2461 > vcpu_block arch/x86/kvm/x86.c:7010 [inline] > vcpu_run arch/x86/kvm/x86.c:7048 [inline] > kvm_arch_vcpu_ioctl_run+0xefc/0x59e0 arch/x86/kvm/x86.c:7207 > kvm_vcpu_ioctl+0x627/0x1100 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2573 > vfs_ioctl fs/ioctl.c:45 [inline] > do_vfs_ioctl+0x1af/0x16d0 fs/ioctl.c:685 > SYSC_ioctl fs/ioctl.c:700 [inline] > SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691 > entry_SYSCALL_64_fastpath+0x1f/0xc2 > RIP: 0033:0x447109 > RSP: 002b:00007ffcb458a038 EFLAGS: 00000202 ORIG_RAX: 0000000000000010 > RAX: ffffffffffffffda RBX: 00000000004002b0 RCX: 0000000000447109 > RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005 > RBP: 0000000000000086 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000 > R13: 00000000004073f0 R14: 0000000000407480 R15: 0000000000000000 > I think we're seeing what Radim describes. So this is now a different call order. The VCPU is set to KVM_MP_STATE_SIPI_RECEIVED (which results in KVM_MP_STATE_INIT_RECEIVED). Then, KVM_SET_VCPU_EVENTS is set with KVM_VCPUEVENT_VALID_SMM | KVM_VCPUEVENT_VALID_NMI_PENDING, enabling SMM. Calling kvm_apic_accept_events() then will result in a warning on the next VCPU run. So the right thing is indeed adding an additional checks for KVM_SET_VCPU_EVENTS. -- Thanks, David