2017-07-11 00:13-0700, Wanpeng Li: > From: Wanpeng Li <wanpeng...@hotmail.com> > > This can be reproduced by EPT=1, unrestricted_guest=N, > emulate_invalid_state=Y > or EPT=0, the trace of kvm-unit-tests/taskswitch2.flat is like below, it > tries > to emulate invalid guest state task-switch: > > kvm_exit: reason TASK_SWITCH rip 0x0 info 40000058 0 > kvm_emulate_insn: 42000:0:0f 0b (0x2) > kvm_emulate_insn: 42000:0:0f 0b (0x2) failed > kvm_inj_exception: #UD (0x0) > kvm_entry: vcpu 0 > kvm_exit: reason TASK_SWITCH rip 0x0 info 40000058 0 > kvm_emulate_insn: 42000:0:0f 0b (0x2) > kvm_emulate_insn: 42000:0:0f 0b (0x2) failed > kvm_inj_exception: #UD (0x0) > ...................... > > It appears that the task-switch emulation updates rflags (and vm86 > flag) only after the segments are loaded, causing vmx->emulation_required > to be set, when in fact invalid guest state emulation is not needed. > > This patch fixes it by updating vmx->emulation_required after the > rflags (and vm86 flag) is updated in task-switch emulation. > > Suggested-by: Nadav Amit <nadav.a...@gmail.com> > Cc: Paolo Bonzini <pbonz...@redhat.com> > Cc: Radim Krčmář <rkrc...@redhat.com> > Cc: Nadav Amit <nadav.a...@gmail.com> > Signed-off-by: Wanpeng Li <wanpeng...@hotmail.com> > --- > arch/x86/kvm/vmx.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index f50cbfd..70270a2 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -6255,6 +6255,7 @@ static int handle_task_switch(struct kvm_vcpu *vcpu) > * TODO: What about debug traps on tss switch? > * Are we supposed to inject them and update dr6? > */ > + vmx->emulation_required = emulation_required(vcpu);
Hm, so the problem happened because changes to rflags can flip the value of emulation_required(). I would add this line to vmx_set_rflags() to make sure that we fixed everything, thanks.
