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From:   Eric Auger <eauger@redhat.com>
Subject: Re: [PATCH v4 13/21] KVM: arm64: Impment SDEI event delivery
To:     Gavin Shan <gshan@redhat.com>, kvmarm@lists.cs.columbia.edu
Cc:     maz@kernel.org, linux-kernel@vger.kernel.org,
        Jonathan.Cameron@huawei.com, pbonzini@redhat.com, will@kernel.org
References: <20210815001352.81927-1-gshan@redhat.com>
 <20210815001352.81927-14-gshan@redhat.com>
Message-ID: <74c5f170-fb08-56a7-ff87-9a51ecfda989@redhat.com>
Date:   Wed, 10 Nov 2021 11:58:57 +0100
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s/Impment/Implement in the commit title

On 8/15/21 2:13 AM, Gavin Shan wrote:
> This implement kvm_sdei_deliver() to support SDEI event delivery.
> The function is called when the request (KVM_REQ_SDEI) is raised.
> The following rules are taken according to the SDEI specification:
> 
>    * x0 - x17 are saved. All of them are cleared except the following
>      registered:
s/registered/registers
>      x0: number SDEI event to be delivered
s/number SDEI event/SDEI event number
>      x1: parameter associated with the SDEI event
user arg?
>      x2: PC of the interrupted context
>      x3: PState of the interrupted context
> 
>    * PC is set to the handler of the SDEI event, which was provided
>      during its registration. PState is modified accordingly.
> 
>    * SDEI event with critical priority can preempt those with normal
>      priority.
> 
> Signed-off-by: Gavin Shan <gshan@redhat.com>
> ---
>  arch/arm64/include/asm/kvm_host.h |  1 +
>  arch/arm64/include/asm/kvm_sdei.h |  1 +
>  arch/arm64/kvm/arm.c              |  3 ++
>  arch/arm64/kvm/sdei.c             | 84 +++++++++++++++++++++++++++++++
>  4 files changed, 89 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index aedf901e1ec7..46f363aa6524 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -47,6 +47,7 @@
>  #define KVM_REQ_RECORD_STEAL	KVM_ARCH_REQ(3)
>  #define KVM_REQ_RELOAD_GICv4	KVM_ARCH_REQ(4)
>  #define KVM_REQ_RELOAD_PMU	KVM_ARCH_REQ(5)
> +#define KVM_REQ_SDEI		KVM_ARCH_REQ(6)
>  
>  #define KVM_DIRTY_LOG_MANUAL_CAPS   (KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE | \
>  				     KVM_DIRTY_LOG_INITIALLY_SET)
> diff --git a/arch/arm64/include/asm/kvm_sdei.h b/arch/arm64/include/asm/kvm_sdei.h
> index b0abc13a0256..7f5f5ad689e6 100644
> --- a/arch/arm64/include/asm/kvm_sdei.h
> +++ b/arch/arm64/include/asm/kvm_sdei.h
> @@ -112,6 +112,7 @@ KVM_SDEI_FLAG_FUNC(enabled)
>  void kvm_sdei_init_vm(struct kvm *kvm);
>  void kvm_sdei_create_vcpu(struct kvm_vcpu *vcpu);
>  int kvm_sdei_hypercall(struct kvm_vcpu *vcpu);
> +void kvm_sdei_deliver(struct kvm_vcpu *vcpu);
>  void kvm_sdei_destroy_vcpu(struct kvm_vcpu *vcpu);
>  void kvm_sdei_destroy_vm(struct kvm *kvm);
>  
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 2f021aa41632..0c3db1ef1ba9 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -689,6 +689,9 @@ static void check_vcpu_requests(struct kvm_vcpu *vcpu)
>  		if (kvm_check_request(KVM_REQ_VCPU_RESET, vcpu))
>  			kvm_reset_vcpu(vcpu);
>  
> +		if (kvm_check_request(KVM_REQ_SDEI, vcpu))
> +			kvm_sdei_deliver(vcpu);
> +
>  		/*
>  		 * Clear IRQ_PENDING requests that were made to guarantee
>  		 * that a VCPU sees new virtual interrupts.
> diff --git a/arch/arm64/kvm/sdei.c b/arch/arm64/kvm/sdei.c
> index 62efee2b67b8..b5d6d1ed3858 100644
> --- a/arch/arm64/kvm/sdei.c
> +++ b/arch/arm64/kvm/sdei.c
> @@ -671,6 +671,90 @@ int kvm_sdei_hypercall(struct kvm_vcpu *vcpu)
>  	return 1;
>  }
>  
> +void kvm_sdei_deliver(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm *kvm = vcpu->kvm;
> +	struct kvm_sdei_kvm *ksdei = kvm->arch.sdei;
> +	struct kvm_sdei_vcpu *vsdei = vcpu->arch.sdei;
> +	struct kvm_sdei_event *kse = NULL;
> +	struct kvm_sdei_kvm_event *kske = NULL;
> +	struct kvm_sdei_vcpu_event *ksve = NULL;
> +	struct kvm_sdei_vcpu_regs *regs = NULL;
> +	unsigned long pstate;
> +	int index = 0;
> +
> +	/* Sanity check */
> +	if (!(ksdei && vsdei))
> +		return;
> +
> +	/* The critical event can't be preempted */
move the comment after the spin_lock
> +	spin_lock(&vsdei->lock);
> +	if (vsdei->critical_event)
> +		goto unlock;
> +
> +	/*
> +	 * The normal event can be preempted by the critical event.
> +	 * However, the normal event can't be preempted by another
> +	 * normal event.
> +	 */
> +	ksve = list_first_entry_or_null(&vsdei->critical_events,
> +			struct kvm_sdei_vcpu_event, link);
> +	if (!ksve && !vsdei->normal_event) {
> +		ksve = list_first_entry_or_null(&vsdei->normal_events,
> +				struct kvm_sdei_vcpu_event, link);
> +	}
At this stage of the review the struct kvm_sdei_vcpu_event lifecycle is
not known.

From the dispatcher pseudocode I understand you check

((IsCriticalEvent(E) and !CriticalEventRunning(P, C)) ||
(!IsCriticalEvent(E) and !EventRunning(P, C)))

but I can't check you take care of
IsEnabled(E) and
IsEventTarget(E, P)
IsUnmasked(P)

Either you should shash with 18/21 or at least you should add comments.
> +
> +	if (!ksve)
> +		goto unlock;
> +
> +	kske = ksve->kske;
> +	kse = kske->kse;
> +	if (kse->state.priority == SDEI_EVENT_PRIORITY_CRITICAL) {
> +		vsdei->critical_event = ksve;
> +		vsdei->state.critical_num = ksve->state.num;
> +		regs = &vsdei->state.critical_regs;
> +	} else {
> +		vsdei->normal_event = ksve;
> +		vsdei->state.normal_num = ksve->state.num;
> +		regs = &vsdei->state.normal_regs;
> +	}
> +
> +	/* Save registers: x0 -> x17, PC, PState */
> +	for (index = 0; index < ARRAY_SIZE(regs->regs); index++)
> +		regs->regs[index] = vcpu_get_reg(vcpu, index);
> +
> +	regs->pc = *vcpu_pc(vcpu);
> +	regs->pstate = *vcpu_cpsr(vcpu);
> +
> +	/*
> +	 * Inject SDEI event: x0 -> x3, PC, PState. We needn't take lock
> +	 * for the KVM event as it can't be destroyed because of its
> +	 * reference count.
> +	 */
> +	for (index = 0; index < ARRAY_SIZE(regs->regs); index++)
> +		vcpu_set_reg(vcpu, index, 0);
> +
> +	index = (kse->state.type == SDEI_EVENT_TYPE_PRIVATE) ?
> +		vcpu->vcpu_idx : 0;
> +	vcpu_set_reg(vcpu, 0, kske->state.num);
> +	vcpu_set_reg(vcpu, 1, kske->state.params[index]);
> +	vcpu_set_reg(vcpu, 2, regs->pc);
> +	vcpu_set_reg(vcpu, 3, regs->pstate);
> +
> +	pstate = regs->pstate;
> +	pstate |= (PSR_D_BIT | PSR_A_BIT | PSR_I_BIT | PSR_F_BIT);
> +	pstate &= ~PSR_MODE_MASK;
> +	pstate |= PSR_MODE_EL1h;
> +	pstate &= ~PSR_MODE32_BIT;
> +
> +	vcpu_write_sys_reg(vcpu, regs->pstate, SPSR_EL1);
> +	*vcpu_cpsr(vcpu) = pstate;
> +	*vcpu_pc(vcpu) = kske->state.entries[index];
> +
> +unlock:
> +	spin_unlock(&vsdei->lock);
> +}
> +
>  void kvm_sdei_init_vm(struct kvm *kvm)
>  {
>  	struct kvm_sdei_kvm *ksdei;
> 
Eric