Date:   Tue, 28 Sep 2021 22:01:58 +0000
From:   David Matlack <dmatlack@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Marc Zyngier <maz@...nel.org>, Huacai Chen <chenhuacai@...nel.org>,
        Aleksandar Markovic <aleksandar.qemu.devel@...il.com>,
        Paul Mackerras <paulus@...abs.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-mips@...r.kernel.org, kvm@...r.kernel.org,
        kvm-ppc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jing Zhang <jingzhangos@...gle.com>
Subject: Re: [PATCH 09/14] KVM: Rename kvm_vcpu_block() => kvm_vcpu_halt()

On Fri, Sep 24, 2021 at 05:55:23PM -0700, Sean Christopherson wrote:
> Rename kvm_vcpu_block() to kvm_vcpu_halt() in preparation for splitting
> the actual "block" sequences into a separate helper (to be named
> kvm_vcpu_block()).  x86 will use the standalone block-only path to handle
> non-halt cases where the vCPU is not runnable.
> 
> Rename block_ns to halt_ns to match the new function name.
> 
> Opportunistically move an x86-specific comment to x86, and enhance it, too.
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Reviewed-by: David Matlack <dmatlack@...gle.com>

> ---
>  arch/arm64/kvm/arch_timer.c       |  2 +-
>  arch/arm64/kvm/handle_exit.c      |  4 ++--
>  arch/arm64/kvm/psci.c             |  2 +-
>  arch/mips/kvm/emulate.c           |  2 +-
>  arch/powerpc/kvm/book3s_pr.c      |  2 +-
>  arch/powerpc/kvm/book3s_pr_papr.c |  2 +-
>  arch/powerpc/kvm/booke.c          |  2 +-
>  arch/powerpc/kvm/powerpc.c        |  2 +-
>  arch/s390/kvm/interrupt.c         |  2 +-
>  arch/x86/kvm/x86.c                | 11 +++++++++--
>  include/linux/kvm_host.h          |  2 +-
>  virt/kvm/kvm_main.c               | 20 +++++++++-----------
>  12 files changed, 29 insertions(+), 24 deletions(-)
> 
> diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c
> index 3df67c127489..7e8396f74010 100644
> --- a/arch/arm64/kvm/arch_timer.c
> +++ b/arch/arm64/kvm/arch_timer.c
> @@ -467,7 +467,7 @@ static void timer_save_state(struct arch_timer_context *ctx)
>  }
>  
>  /*
> - * Schedule the background timer before calling kvm_vcpu_block, so that this
> + * Schedule the background timer before calling kvm_vcpu_halt, so that this
>   * thread is removed from its waitqueue and made runnable when there's a timer
>   * interrupt to handle.
>   */
> diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
> index 275a27368a04..08f823984712 100644
> --- a/arch/arm64/kvm/handle_exit.c
> +++ b/arch/arm64/kvm/handle_exit.c
> @@ -82,7 +82,7 @@ static int handle_no_fpsimd(struct kvm_vcpu *vcpu)
>   *
>   * WFE: Yield the CPU and come back to this vcpu when the scheduler
>   * decides to.
> - * WFI: Simply call kvm_vcpu_block(), which will halt execution of
> + * WFI: Simply call kvm_vcpu_halt(), which will halt execution of
>   * world-switches and schedule other host processes until there is an
>   * incoming IRQ or FIQ to the VM.
>   */
> @@ -95,7 +95,7 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu)
>  	} else {
>  		trace_kvm_wfx_arm64(*vcpu_pc(vcpu), false);
>  		vcpu->stat.wfi_exit_stat++;
> -		kvm_vcpu_block(vcpu);
> +		kvm_vcpu_halt(vcpu);
>  		kvm_clear_request(KVM_REQ_UNHALT, vcpu);
>  	}
>  
> diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
> index 74c47d420253..e275b2ca08b9 100644
> --- a/arch/arm64/kvm/psci.c
> +++ b/arch/arm64/kvm/psci.c
> @@ -46,7 +46,7 @@ static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu)
>  	 * specification (ARM DEN 0022A). This means all suspend states
>  	 * for KVM will preserve the register state.
>  	 */
> -	kvm_vcpu_block(vcpu);
> +	kvm_vcpu_halt(vcpu);
>  	kvm_clear_request(KVM_REQ_UNHALT, vcpu);
>  
>  	return PSCI_RET_SUCCESS;
> diff --git a/arch/mips/kvm/emulate.c b/arch/mips/kvm/emulate.c
> index 22e745e49b0a..b494d8d39290 100644
> --- a/arch/mips/kvm/emulate.c
> +++ b/arch/mips/kvm/emulate.c
> @@ -952,7 +952,7 @@ enum emulation_result kvm_mips_emul_wait(struct kvm_vcpu *vcpu)
>  	if (!vcpu->arch.pending_exceptions) {
>  		kvm_vz_lose_htimer(vcpu);
>  		vcpu->arch.wait = 1;
> -		kvm_vcpu_block(vcpu);
> +		kvm_vcpu_halt(vcpu);
>  
>  		/*
>  		 * We we are runnable, then definitely go off to user space to
> diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
> index 6bc9425acb32..0ced1b16f0e5 100644
> --- a/arch/powerpc/kvm/book3s_pr.c
> +++ b/arch/powerpc/kvm/book3s_pr.c
> @@ -492,7 +492,7 @@ static void kvmppc_set_msr_pr(struct kvm_vcpu *vcpu, u64 msr)
>  
>  	if (msr & MSR_POW) {
>  		if (!vcpu->arch.pending_exceptions) {
> -			kvm_vcpu_block(vcpu);
> +			kvm_vcpu_halt(vcpu);
>  			kvm_clear_request(KVM_REQ_UNHALT, vcpu);
>  			vcpu->stat.generic.halt_wakeup++;
>  
> diff --git a/arch/powerpc/kvm/book3s_pr_papr.c b/arch/powerpc/kvm/book3s_pr_papr.c
> index ac14239f3424..1f10e7dfcdd0 100644
> --- a/arch/powerpc/kvm/book3s_pr_papr.c
> +++ b/arch/powerpc/kvm/book3s_pr_papr.c
> @@ -376,7 +376,7 @@ int kvmppc_h_pr(struct kvm_vcpu *vcpu, unsigned long cmd)
>  		return kvmppc_h_pr_stuff_tce(vcpu);
>  	case H_CEDE:
>  		kvmppc_set_msr_fast(vcpu, kvmppc_get_msr(vcpu) | MSR_EE);
> -		kvm_vcpu_block(vcpu);
> +		kvm_vcpu_halt(vcpu);
>  		kvm_clear_request(KVM_REQ_UNHALT, vcpu);
>  		vcpu->stat.generic.halt_wakeup++;
>  		return EMULATE_DONE;
> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
> index 977801c83aff..12abffa40cd9 100644
> --- a/arch/powerpc/kvm/booke.c
> +++ b/arch/powerpc/kvm/booke.c
> @@ -718,7 +718,7 @@ int kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
>  
>  	if (vcpu->arch.shared->msr & MSR_WE) {
>  		local_irq_enable();
> -		kvm_vcpu_block(vcpu);
> +		kvm_vcpu_halt(vcpu);
>  		kvm_clear_request(KVM_REQ_UNHALT, vcpu);
>  		hard_irq_disable();
>  
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 8ab90ce8738f..565eed2dab81 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -236,7 +236,7 @@ int kvmppc_kvm_pv(struct kvm_vcpu *vcpu)
>  		break;
>  	case EV_HCALL_TOKEN(EV_IDLE):
>  		r = EV_SUCCESS;
> -		kvm_vcpu_block(vcpu);
> +		kvm_vcpu_halt(vcpu);
>  		kvm_clear_request(KVM_REQ_UNHALT, vcpu);
>  		break;
>  	default:
> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
> index 520450a7956f..10bd648170b7 100644
> --- a/arch/s390/kvm/interrupt.c
> +++ b/arch/s390/kvm/interrupt.c
> @@ -1335,7 +1335,7 @@ int kvm_s390_handle_wait(struct kvm_vcpu *vcpu)
>  	VCPU_EVENT(vcpu, 4, "enabled wait: %llu ns", sltime);
>  no_timer:
>  	srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> -	kvm_vcpu_block(vcpu);
> +	kvm_vcpu_halt(vcpu);
>  	vcpu->valid_wakeup = false;
>  	__unset_cpu_idle(vcpu);
>  	vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index eade8a2bdccf..0d71c73a61bb 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -8645,6 +8645,13 @@ void kvm_arch_exit(void)
>  
>  static int __kvm_emulate_halt(struct kvm_vcpu *vcpu, int state, int reason)
>  {
> +	/*
> +	 * The vCPU has halted, e.g. executed HLT.  Update the run state if the
> +	 * local APIC is in-kernel, the run loop will detect the non-runnable
> +	 * state and halt the vCPU.  Exit to userspace if the local APIC is
> +	 * managed by userspace, in which case userspace is responsible for
> +	 * handling wake events.
> +	 */
>  	++vcpu->stat.halt_exits;
>  	if (lapic_in_kernel(vcpu)) {
>  		vcpu->arch.mp_state = state;
> @@ -9886,7 +9893,7 @@ static inline int vcpu_block(struct kvm *kvm, struct kvm_vcpu *vcpu)
>  	if (!kvm_arch_vcpu_runnable(vcpu) &&
>  	    (!kvm_x86_ops.pre_block || static_call(kvm_x86_pre_block)(vcpu) == 0)) {
>  		srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
> -		kvm_vcpu_block(vcpu);
> +		kvm_vcpu_halt(vcpu);
>  		vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
>  
>  		if (kvm_x86_ops.post_block)
> @@ -10120,7 +10127,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
>  			r = -EINTR;
>  			goto out;
>  		}
> -		kvm_vcpu_block(vcpu);
> +		kvm_vcpu_halt(vcpu);
>  		if (kvm_apic_accept_events(vcpu) < 0) {
>  			r = 0;
>  			goto out;
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 3f87d6ad20bf..d2a8be3fb9ba 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -965,7 +965,7 @@ void kvm_vcpu_mark_page_dirty(struct kvm_vcpu *vcpu, gfn_t gfn);
>  void kvm_sigset_activate(struct kvm_vcpu *vcpu);
>  void kvm_sigset_deactivate(struct kvm_vcpu *vcpu);
>  
> -void kvm_vcpu_block(struct kvm_vcpu *vcpu);
> +void kvm_vcpu_halt(struct kvm_vcpu *vcpu);
>  void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu);
>  void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu);
>  bool kvm_vcpu_wake_up(struct kvm_vcpu *vcpu);
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index f96cda8312f3..280cf1dca7db 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -3221,16 +3221,13 @@ static inline void update_halt_poll_stats(struct kvm_vcpu *vcpu, ktime_t start,
>  	}
>  }
>  
> -/*
> - * The vCPU has executed a HLT instruction with in-kernel mode enabled.
> - */
> -void kvm_vcpu_block(struct kvm_vcpu *vcpu)
> +void kvm_vcpu_halt(struct kvm_vcpu *vcpu)
>  {
>  	bool halt_poll_allowed = !kvm_arch_no_poll(vcpu);
>  	bool do_halt_poll = halt_poll_allowed && vcpu->halt_poll_ns;
>  	ktime_t start, cur, poll_end;
>  	bool waited = false;
> -	u64 block_ns;
> +	u64 halt_ns;
>  
>  	start = cur = poll_end = ktime_get();
>  	if (do_halt_poll) {
> @@ -3273,7 +3270,8 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
>  	}
>  
>  out:
> -	block_ns = ktime_to_ns(cur) - ktime_to_ns(start);
> +	/* The total time the vCPU was "halted", including polling time. */
> +	halt_ns = ktime_to_ns(cur) - ktime_to_ns(start);
>  
>  	/*
>  	 * Note, halt-polling is considered successful so long as the vCPU was
> @@ -3287,24 +3285,24 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
>  		if (!vcpu_valid_wakeup(vcpu)) {
>  			shrink_halt_poll_ns(vcpu);
>  		} else if (vcpu->kvm->max_halt_poll_ns) {
> -			if (block_ns <= vcpu->halt_poll_ns)
> +			if (halt_ns <= vcpu->halt_poll_ns)
>  				;
>  			/* we had a long block, shrink polling */
>  			else if (vcpu->halt_poll_ns &&
> -					block_ns > vcpu->kvm->max_halt_poll_ns)
> +				 halt_ns > vcpu->kvm->max_halt_poll_ns)
>  				shrink_halt_poll_ns(vcpu);
>  			/* we had a short halt and our poll time is too small */
>  			else if (vcpu->halt_poll_ns < vcpu->kvm->max_halt_poll_ns &&
> -					block_ns < vcpu->kvm->max_halt_poll_ns)
> +				 halt_ns < vcpu->kvm->max_halt_poll_ns)
>  				grow_halt_poll_ns(vcpu);
>  		} else {
>  			vcpu->halt_poll_ns = 0;
>  		}
>  	}
>  
> -	trace_kvm_vcpu_wakeup(block_ns, waited, vcpu_valid_wakeup(vcpu));
> +	trace_kvm_vcpu_wakeup(halt_ns, waited, vcpu_valid_wakeup(vcpu));
>  }
> -EXPORT_SYMBOL_GPL(kvm_vcpu_block);
> +EXPORT_SYMBOL_GPL(kvm_vcpu_halt);
>  
>  bool kvm_vcpu_wake_up(struct kvm_vcpu *vcpu)
>  {
> -- 
> 2.33.0.685.g46640cef36-goog
> 

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