2017-08-22 0:20 GMT+08:00 Radim Krčmář <rkrcmar@xxxxxxxxxx>: > 2017-08-18 07:11-0700, Wanpeng Li: >> From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> >> >> ------------[ cut here ]------------ >> WARNING: CPU: 7 PID: 3861 at /home/kernel/ssd/kvm/arch/x86/kvm//vmx.c:11299 nested_vmx_vmexit+0x176e/0x1980 [kvm_intel] >> CPU: 7 PID: 3861 Comm: qemu-system-x86 Tainted: G W OE 4.13.0-rc4+ #11 >> RIP: 0010:nested_vmx_vmexit+0x176e/0x1980 [kvm_intel] >> Call Trace: >> ? kvm_multiple_exception+0x149/0x170 [kvm] >> ? handle_emulation_failure+0x79/0x230 [kvm] >> ? load_vmcs12_host_state+0xa80/0xa80 [kvm_intel] >> ? check_chain_key+0x137/0x1e0 >> ? reexecute_instruction.part.168+0x130/0x130 [kvm] >> nested_vmx_inject_exception_vmexit+0xb7/0x100 [kvm_intel] >> ? nested_vmx_inject_exception_vmexit+0xb7/0x100 [kvm_intel] >> vmx_queue_exception+0x197/0x300 [kvm_intel] >> kvm_arch_vcpu_ioctl_run+0x1b0c/0x2c90 [kvm] >> ? kvm_arch_vcpu_runnable+0x220/0x220 [kvm] >> ? preempt_count_sub+0x18/0xc0 >> ? restart_apic_timer+0x17d/0x300 [kvm] >> ? kvm_lapic_restart_hv_timer+0x37/0x50 [kvm] >> ? kvm_arch_vcpu_load+0x1d8/0x350 [kvm] >> kvm_vcpu_ioctl+0x4e4/0x910 [kvm] >> ? kvm_vcpu_ioctl+0x4e4/0x910 [kvm] >> ? kvm_dev_ioctl+0xbe0/0xbe0 [kvm] >> >> The flag "nested_run_pending", which can override the decision of which should run >> next, L1 or L2. nested_run_pending=1 means that we *must* run L2 next, not L1. This >> is necessary in particular when L1 did a VMLAUNCH of L2 and therefore expects L2 to >> be run (and perhaps be injected with an event it specified, etc.). Nested_run_pending >> is especially intended to avoid switching to L1 in the injection decision-point. >> >> I catch this in the queue exception path, this patch fixes it by requesting >> an immediate VM exit from L2 and keeping the exception for L1 pending for a >> subsequent nested VM exit. >> >> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> >> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx> >> Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> >> --- >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >> @@ -6356,8 +6356,8 @@ static int inject_pending_event(struct kvm_vcpu *vcpu, bool req_int_win) >> kvm_update_dr7(vcpu); >> } > > Hm, we shouldn't execute the code above if exception won't be injected. > >> >> - kvm_x86_ops->queue_exception(vcpu); >> - return 0; > > vmx_complete_interrupts() assumes that the exception is always injected, > so it would be dropped by kvm_clear_exception_queue(). > > I'm starting to wonder whether getting rid of nested_run_pending > wouldn't be nicer. Yeah, I rethink of your concern for nested_run_pending w/ return value is 0, actually the path in the calltrace is the else branch in nested_vmx_check_exception(), an exception will be injected to L2 by L1 if L1 owns this exception, otherwise injected by L0 directly. For the nested_run_pending w/ return value is 0 stuff, we can treat it as L0 injects the exception to L2 directly. So there is no exception is injected to wrong guest. Regards, Wanpeng Li
