linux-kernel - Re: [PATCH v4 12/21] KVM: arm64: Support SDEI_{PRIVATE, SHARED}

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Date:   Tue, 9 Nov 2021 21:37:43 +0100
From:   Eric Auger <eauger@...hat.com>
To:     Gavin Shan <gshan@...hat.com>, kvmarm@...ts.cs.columbia.edu
Cc:     maz@...nel.org, linux-kernel@...r.kernel.org,
        Jonathan.Cameron@...wei.com, pbonzini@...hat.com, will@...nel.org
Subject: Re: [PATCH v4 12/21] KVM: arm64: Support SDEI_{PRIVATE, SHARED}_RESET
 hypercall



On 8/15/21 2:13 AM, Gavin Shan wrote:
> This supports SDEI_{PRIVATE, SHARED}_RESET. They are used by the
> guest to purge the private or shared SDEI events, which are registered
to reset all private SDEI event registrations of the calling PE (resp.
PRIVATE or SHARED)
> previously.
> 
> Signed-off-by: Gavin Shan <gshan@...hat.com>
> ---
>  arch/arm64/kvm/sdei.c | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/arch/arm64/kvm/sdei.c b/arch/arm64/kvm/sdei.c
> index 3fb33258b494..62efee2b67b8 100644
> --- a/arch/arm64/kvm/sdei.c
> +++ b/arch/arm64/kvm/sdei.c
> @@ -582,6 +582,29 @@ static unsigned long kvm_sdei_hypercall_mask(struct kvm_vcpu *vcpu,
>  	return ret;
>  }
>  
> +static unsigned long kvm_sdei_hypercall_reset(struct kvm_vcpu *vcpu,
> +					      bool private)
> +{
> +	struct kvm *kvm = vcpu->kvm;
> +	struct kvm_sdei_kvm *ksdei = kvm->arch.sdei;
> +	struct kvm_sdei_vcpu *vsdei = vcpu->arch.sdei;
> +	unsigned int mask = private ? (1 << SDEI_EVENT_TYPE_PRIVATE) :
> +				      (1 << SDEI_EVENT_TYPE_SHARED);
> +	unsigned long ret = SDEI_SUCCESS;
> +
> +	/* Sanity check */
> +	if (!(ksdei && vsdei)) {
> +		ret = SDEI_NOT_SUPPORTED;
> +		goto out;
> +	}
> +
> +	spin_lock(&ksdei->lock);
> +	kvm_sdei_remove_kvm_events(kvm, mask, false);
With kvm_sdei_remove_kvm_events() implementation, why do you make sure
that events which have a running handler get unregistered once the
handler completes? I just see the refcount check that prevents the "KVM
event object" from being removed.
> +	spin_unlock(&ksdei->lock);
> +out:
> +	return ret;
> +}
> +
>  int kvm_sdei_hypercall(struct kvm_vcpu *vcpu)
>  {
>  	u32 func = smccc_get_function(vcpu);
> @@ -626,8 +649,14 @@ int kvm_sdei_hypercall(struct kvm_vcpu *vcpu)
>  		break;
>  	case SDEI_1_0_FN_SDEI_INTERRUPT_BIND:
>  	case SDEI_1_0_FN_SDEI_INTERRUPT_RELEASE:
> +		ret = SDEI_NOT_SUPPORTED;
> +		break;
>  	case SDEI_1_0_FN_SDEI_PRIVATE_RESET:
> +		ret = kvm_sdei_hypercall_reset(vcpu, true);
> +		break;
>  	case SDEI_1_0_FN_SDEI_SHARED_RESET:
> +		ret = kvm_sdei_hypercall_reset(vcpu, false);
> +		break;
>  	default:
>  		ret = SDEI_NOT_SUPPORTED;
>  	}
> 
Eric