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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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