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    SubjectRe: [PATCH v2 12/43] KVM: x86: Tweak halt emulation helper names to free up kvm_vcpu_halt()
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    On Wed, 2021-10-27 at 17:10 +0300, Maxim Levitsky wrote:
    > On Fri, 2021-10-08 at 19:12 -0700, Sean Christopherson wrote:
    > > Rename a variety of HLT-related helpers to free up the function name
    > > "kvm_vcpu_halt" for future use in generic KVM code, e.g. to differentiate
    > > between "block" and "halt".
    > >
    > > No functional change intended.
    > >
    > > Reviewed-by: David Matlack <dmatlack@google.com>
    > > Signed-off-by: Sean Christopherson <seanjc@google.com>
    > > ---
    > > arch/x86/include/asm/kvm_host.h | 2 +-
    > > arch/x86/kvm/vmx/nested.c | 2 +-
    > > arch/x86/kvm/vmx/vmx.c | 4 ++--
    > > arch/x86/kvm/x86.c | 13 +++++++------
    > > 4 files changed, 11 insertions(+), 10 deletions(-)
    > >
    > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
    > > index 7aafc27ce7a9..328103a520d3 100644
    > > --- a/arch/x86/include/asm/kvm_host.h
    > > +++ b/arch/x86/include/asm/kvm_host.h
    > > @@ -1689,7 +1689,7 @@ int kvm_emulate_monitor(struct kvm_vcpu *vcpu);
    > > int kvm_fast_pio(struct kvm_vcpu *vcpu, int size, unsigned short port, int in);
    > > int kvm_emulate_cpuid(struct kvm_vcpu *vcpu);
    > > int kvm_emulate_halt(struct kvm_vcpu *vcpu);
    > > -int kvm_vcpu_halt(struct kvm_vcpu *vcpu);
    > > +int kvm_emulate_halt_noskip(struct kvm_vcpu *vcpu);
    > > int kvm_emulate_ap_reset_hold(struct kvm_vcpu *vcpu);
    > > int kvm_emulate_wbinvd(struct kvm_vcpu *vcpu);
    > >
    > > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
    > > index af1bbb73430a..d0237a441feb 100644
    > > --- a/arch/x86/kvm/vmx/nested.c
    > > +++ b/arch/x86/kvm/vmx/nested.c
    > > @@ -3619,7 +3619,7 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
    > > !(nested_cpu_has(vmcs12, CPU_BASED_INTR_WINDOW_EXITING) &&
    > > (vmcs12->guest_rflags & X86_EFLAGS_IF))) {
    > > vmx->nested.nested_run_pending = 0;
    > > - return kvm_vcpu_halt(vcpu);
    > > + return kvm_emulate_halt_noskip(vcpu);
    > > }
    > > break;
    > > case GUEST_ACTIVITY_WAIT_SIPI:
    > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
    > > index 1c8b2b6e7ed9..5517893f12fc 100644
    > > --- a/arch/x86/kvm/vmx/vmx.c
    > > +++ b/arch/x86/kvm/vmx/vmx.c
    > > @@ -4741,7 +4741,7 @@ static int handle_rmode_exception(struct kvm_vcpu *vcpu,
    > > if (kvm_emulate_instruction(vcpu, 0)) {
    > > if (vcpu->arch.halt_request) {
    > > vcpu->arch.halt_request = 0;
    > > - return kvm_vcpu_halt(vcpu);
    > > + return kvm_emulate_halt_noskip(vcpu);
    >
    > Could you elaborate on why you choose _noskip suffix?
    >
    > As far as I see, kvm_vcpu_halt just calls __kvm_vcpu_halt with new VCPU run state/exit reason,
    > which is used only when local apic is not in the kernel (which is these days not that
    > supported configuration).
    >
    > Other user of __kvm_vcpu_halt is something SEV related.
    >
    > Best regards,
    > Maxim Levitsky
    >
    >
    > > }
    > > return 1;
    > > }
    > > @@ -5415,7 +5415,7 @@ static int handle_invalid_guest_state(struct kvm_vcpu *vcpu)
    > >
    > > if (vcpu->arch.halt_request) {
    > > vcpu->arch.halt_request = 0;
    > > - return kvm_vcpu_halt(vcpu);
    > > + return kvm_emulate_halt_noskip(vcpu);
    > > }
    > >
    > > /*
    > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    > > index 4a52a08707de..9c23ae1d483d 100644
    > > --- a/arch/x86/kvm/x86.c
    > > +++ b/arch/x86/kvm/x86.c
    > > @@ -8649,7 +8649,7 @@ void kvm_arch_exit(void)
    > > #endif
    > > }
    > >
    > > -static int __kvm_vcpu_halt(struct kvm_vcpu *vcpu, int state, int reason)
    > > +static int __kvm_emulate_halt(struct kvm_vcpu *vcpu, int state, int reason)
    > > {
    > > ++vcpu->stat.halt_exits;
    > > if (lapic_in_kernel(vcpu)) {
    > > @@ -8661,11 +8661,11 @@ static int __kvm_vcpu_halt(struct kvm_vcpu *vcpu, int state, int reason)
    > > }
    > > }
    > >
    > > -int kvm_vcpu_halt(struct kvm_vcpu *vcpu)
    > > +int kvm_emulate_halt_noskip(struct kvm_vcpu *vcpu)
    > > {
    > > - return __kvm_vcpu_halt(vcpu, KVM_MP_STATE_HALTED, KVM_EXIT_HLT);
    > > + return __kvm_emulate_halt(vcpu, KVM_MP_STATE_HALTED, KVM_EXIT_HLT);
    > > }
    > > -EXPORT_SYMBOL_GPL(kvm_vcpu_halt);
    > > +EXPORT_SYMBOL_GPL(kvm_emulate_halt_noskip);
    > >
    > > int kvm_emulate_halt(struct kvm_vcpu *vcpu)
    > > {
    > > @@ -8674,7 +8674,7 @@ int kvm_emulate_halt(struct kvm_vcpu *vcpu)
    > > * TODO: we might be squashing a GUESTDBG_SINGLESTEP-triggered
    > > * KVM_EXIT_DEBUG here.
    > > */
    > > - return kvm_vcpu_halt(vcpu) && ret;
    > > + return kvm_emulate_halt_noskip(vcpu) && ret;
    > > }
    > > EXPORT_SYMBOL_GPL(kvm_emulate_halt);
    > >
    > > @@ -8682,7 +8682,8 @@ int kvm_emulate_ap_reset_hold(struct kvm_vcpu *vcpu)
    > > {
    > > int ret = kvm_skip_emulated_instruction(vcpu);
    > >
    > > - return __kvm_vcpu_halt(vcpu, KVM_MP_STATE_AP_RESET_HOLD, KVM_EXIT_AP_RESET_HOLD) && ret;
    > > + return __kvm_emulate_halt(vcpu, KVM_MP_STATE_AP_RESET_HOLD,
    > > + KVM_EXIT_AP_RESET_HOLD) && ret;
    > > }
    > > EXPORT_SYMBOL_GPL(kvm_emulate_ap_reset_hold);
    > >

    Also while at it, why not to use say '__kvm_emulate_hlt' ('hlt' instead of 'halt') to
    put emphasis on the fact that we are emulating a cpu instruction?

    Best regards,
    Maxim Levitsky


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