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SubjectRe: [PATCH 5/5] KVM: VMX: Handle RFLAGS.TF in skip_emulated_instruction
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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

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