Re: [PATCH] KVM: x86: respect singlestep when emulating instruction

On May 18, 2020, at 11:38 PM, Paolo Bonzini pbonzini@redhat.com wrote:

On 18/05/20 23:36, Felipe Franciosi wrote:

...

    exception_type(ctxt->exception.vector) == EXCPT_TRAP) {
	kvm_rip_write(vcpu, ctxt->eip);

• 	if (r && ctxt->tf)
  

• 	if ((r && ctxt->tf) || (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP))
  	r = kvm_vcpu_do_singlestep(vcpu);
  

Almost:

if (r && (ctxt->tf || (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP))

This is because if r == 0 you have to exit to userspace with KVM_EXIT_MMIO and KVM_EXIT_IO before completing execution of the instruction. Once this is done, you'll get here again and you'll be able to go through kvm_vcpu_do_singlestep.

AHH yeah. I tested *only* with SINGLESTEP enabled and I didn't do any MMIO/PIO, so I didn't even realise it. Thanks. Sending v2.

F.

Thanks,

Paolo