linux-kernel - Re: [PATCH v6 06/18] KVM: arm64: Support SDEI_EVENT

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Date:   Sat, 30 Apr 2022 15:03:36 +0000
From:   Oliver Upton <oupton@...gle.com>
To:     Gavin Shan <gshan@...hat.com>
Cc:     kvmarm@...ts.cs.columbia.edu, linux-kernel@...r.kernel.org,
        eauger@...hat.com, Jonathan.Cameron@...wei.com,
        vkuznets@...hat.com, will@...nel.org, shannon.zhaosl@...il.com,
        james.morse@....com, mark.rutland@....com, maz@...nel.org,
        pbonzini@...hat.com, shan.gavin@...il.com
Subject: Re: [PATCH v6 06/18] KVM: arm64: Support SDEI_EVENT_CONTEXT hypercall

On Sun, Apr 03, 2022 at 11:38:59PM +0800, Gavin Shan wrote:
> This supports SDEI_EVENT_CONTEXT hypercall. It's used by the guest
> to retrieve the registers (x0 - x17) from the interrupted or preempted
> context in the event handler. The interrupted or preempted context
> is saved prior to handling the event by executing its handler and
> restored after that.
> 
> Signed-off-by: Gavin Shan <gshan@...hat.com>
> ---
>  arch/arm64/kvm/sdei.c | 34 ++++++++++++++++++++++++++++++++++
>  1 file changed, 34 insertions(+)
> 
> diff --git a/arch/arm64/kvm/sdei.c b/arch/arm64/kvm/sdei.c
> index 941263578b30..af5d11b8eb2f 100644
> --- a/arch/arm64/kvm/sdei.c
> +++ b/arch/arm64/kvm/sdei.c
> @@ -140,6 +140,37 @@ static unsigned long hypercall_enable(struct kvm_vcpu *vcpu, bool enable)
>  	return ret;
>  }
>  
> +static unsigned long hypercall_context(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm_sdei_vcpu *vsdei = vcpu->arch.sdei;
> +	struct kvm_sdei_vcpu_context *context;
> +	unsigned long param_id = smccc_get_arg(vcpu, 1);
> +	unsigned long ret = SDEI_SUCCESS;
> +
> +	spin_lock(&vsdei->lock);
> +
> +	/* Check if we have events are being handled */
> +	context = &vsdei->context[SDEI_EVENT_PRIORITY_CRITICAL];
> +	context = context->event ? context : NULL;
> +	context = context ? : &vsdei->context[SDEI_EVENT_PRIORITY_NORMAL];
> +	context = context->event ? context : NULL;
> +	if (!context) {
> +		ret = SDEI_DENIED;
> +		goto unlock;
> +	}

Eek! You'll probably be able to drop all of this and just check the SDEI
active flag.

--
Thanks,
Oliver