Re: [PATCH v2 12/43] KVM: x86: Tweak halt emulation helper names to free up kvm_vcpu_halt()

From: Maxim Levitsky
Date: Wed Oct 27 2021 - 10:10:56 EST


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@xxxxxxxxxx>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
> 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);
>