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Subject: Re: [PATCH v4 19/21] KVM: arm64: Support SDEI event cancellation
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>
 <20210815001352.81927-20-gshan@redhat.com>
From:   Eric Auger <eauger@redhat.com>
Message-ID: <6557af7a-ca00-d9dd-c970-3e85c81d1582@redhat.com>
Date:   Wed, 10 Nov 2021 15:09:57 +0100
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On 8/15/21 2:13 AM, Gavin Shan wrote:
> The injected SDEI event is to send notification to guest. The SDEI
> event might not be needed after it's injected. This introduces API
> to support cancellation on the injected SDEI event if it's not fired
> to the guest yet.
> 
> This mechanism will be needed when we're going to support asynchronous
> page fault.

if we are able to manage the migration of an executing SDEI why can't we
manage the migration of pending SDEIs?

Eric
> 
> Signed-off-by: Gavin Shan <gshan@redhat.com>
> ---
>  arch/arm64/include/asm/kvm_sdei.h |  1 +
>  arch/arm64/kvm/sdei.c             | 49 +++++++++++++++++++++++++++++++
>  2 files changed, 50 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/kvm_sdei.h b/arch/arm64/include/asm/kvm_sdei.h
> index 51087fe971ba..353744c7bad9 100644
> --- a/arch/arm64/include/asm/kvm_sdei.h
> +++ b/arch/arm64/include/asm/kvm_sdei.h
> @@ -126,6 +126,7 @@ int kvm_sdei_register_notifier(struct kvm *kvm, unsigned long num,
>  			       kvm_sdei_notifier notifier);
>  int kvm_sdei_inject(struct kvm_vcpu *vcpu,
>  		    unsigned long num, bool immediate);
> +int kvm_sdei_cancel(struct kvm_vcpu *vcpu, unsigned long num);
>  void kvm_sdei_deliver(struct kvm_vcpu *vcpu);
>  long kvm_sdei_vm_ioctl(struct kvm *kvm, unsigned long arg);
>  long kvm_sdei_vcpu_ioctl(struct kvm_vcpu *vcpu, unsigned long arg);
> diff --git a/arch/arm64/kvm/sdei.c b/arch/arm64/kvm/sdei.c
> index 7c2789cd1421..4f5a582daa97 100644
> --- a/arch/arm64/kvm/sdei.c
> +++ b/arch/arm64/kvm/sdei.c
> @@ -907,6 +907,55 @@ int kvm_sdei_inject(struct kvm_vcpu *vcpu,
>  	return ret;
>  }
>  
> +int kvm_sdei_cancel(struct kvm_vcpu *vcpu, unsigned long num)
> +{
> +	struct kvm *kvm = vcpu->kvm;
> +	struct kvm_sdei_kvm *ksdei = kvm->arch.sdei;
> +	struct kvm_sdei_vcpu *vsdei = vcpu->arch.sdei;
> +	struct kvm_sdei_kvm_event *kske = NULL;
> +	struct kvm_sdei_vcpu_event *ksve = NULL;
> +	int ret = 0;
> +
> +	if (!(ksdei && vsdei)) {
> +		ret = -EPERM;
> +		goto out;
> +	}
> +
> +	/* Find the vCPU event */
> +	spin_lock(&vsdei->lock);
> +	ksve = kvm_sdei_find_vcpu_event(vcpu, num);
> +	if (!ksve) {
> +		ret = -EINVAL;
> +		goto unlock;
> +	}
> +
> +	/* Event can't be cancelled if it has been delivered */
> +	if (ksve->state.refcount <= 1 &&
> +	    (vsdei->critical_event == ksve ||
> +	     vsdei->normal_event == ksve)) {
> +		ret = -EINPROGRESS;
> +		goto unlock;
> +	}
> +
> +	/* Free the vCPU event if necessary */
> +	kske = ksve->kske;
> +	ksve->state.refcount--;
> +	if (!ksve->state.refcount) {
> +		list_del(&ksve->link);
> +		kfree(ksve);
> +	}
> +
> +unlock:
> +	spin_unlock(&vsdei->lock);
> +	if (kske) {
> +		spin_lock(&ksdei->lock);
> +		kske->state.refcount--;
> +		spin_unlock(&ksdei->lock);
> +	}
> +out:
> +	return ret;
> +}
> +
>  void kvm_sdei_deliver(struct kvm_vcpu *vcpu)
>  {
>  	struct kvm *kvm = vcpu->kvm;
>