On Mon, Nov 28, 2016 at 3:42 AM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>
>
> On 28/11/2016 05:18, Kyle Huey wrote:
>> +
>> + if (unlikely(vmx_get_rflags(vcpu) & X86_EFLAGS_TF)) {
>> + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
>> + vcpu->run->debug.arch.dr6 = DR6_BS | DR6_FIXED_1 |
>> + DR6_RTM;
>> + vcpu->run->debug.arch.pc = vcpu->arch.singlestep_rip;
>> + vcpu->run->debug.arch.exception = DB_VECTOR;
>> + vcpu->run->exit_reason = KVM_EXIT_DEBUG;
>> + return 0;
>> + }
>> +
>> + /*
>> + * "Certain debug exceptions may clear bit 0-3. The
>> + * remaining contents of the DR6 register are never
>> + * cleared by the processor".
>> + */
>> + vcpu->arch.dr6 &= ~15;
>> + vcpu->arch.dr6 |= DR6_BS | DR6_RTM;
>> + kvm_queue_exception(vcpu, DB_VECTOR);
>> + }
>
> This code is pretty much the same as kvm_vcpu_check_singlestep. Let's
> not duplicate the code and implement skip_emulated_instruction can be
> implemented in x86.c, like
>
> unsigned long rflags = kvm_x86_ops->get_rflags(vcpu);
> int r = EMULATE_DONE;
>
> /* This would be the no_trap variant */
> kvm_x86_ops->skip_emulated_instruction(vcpu);
> kvm_vcpu_check_singlestep(vcpu, rflags, &r);
> return r == EMULATE_DONE;
>
> (because x86.c/vmx.c/svm.c are separate modules, when moving the function
> to x86.c you should rename it to kvm_skip_emulated_instruction).
>
> Paolo
They're not exactly the same. For some reason I don't understand
kvm_vcpu_check_singlestep clears the trap flag. Perhaps that is also
a bug?
- Kyle
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