linux-kernel - Re: [PATCH v6 14/18] KVM: arm64: Support SDEI_EVENT

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Message-ID: <Ym2q2fUwPXNDcMjQ@google.com>
Date:   Sat, 30 Apr 2022 21:32:09 +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 14/18] KVM: arm64: Support SDEI_EVENT_SIGNAL hypercall

Hi Gavin,

On Sun, Apr 03, 2022 at 11:39:07PM +0800, Gavin Shan wrote:
> This supports SDEI_EVENT_SIGNAL hypercall. It's used by guest
> to inject event, whose number must be zero to the specified
> vCPU. As the shared event isn't supported, calling vCPU is
> assumed to be the target.
> 
> Signed-off-by: Gavin Shan <gshan@...hat.com>
> ---
>  arch/arm64/kvm/sdei.c | 45 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 45 insertions(+)
> 
> diff --git a/arch/arm64/kvm/sdei.c b/arch/arm64/kvm/sdei.c
> index ebdbe7810cf0..e1f6ab9800ee 100644
> --- a/arch/arm64/kvm/sdei.c
> +++ b/arch/arm64/kvm/sdei.c
> @@ -455,6 +455,48 @@ static unsigned long hypercall_mask(struct kvm_vcpu *vcpu, bool mask)
>  	return ret;
>  }
>  
> +static unsigned long hypercall_signal(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm_sdei_vcpu *vsdei = vcpu->arch.sdei;
> +	struct kvm_sdei_event *event;
> +	unsigned int num = smccc_get_arg(vcpu, 1);
> +	unsigned long ret = SDEI_SUCCESS;
> +
> +	/*
> +	 * The event must be the software signaled one, whose number
> +	 * is zero.
> +	 */
> +	if (!kvm_sdei_is_sw_signaled(num)) {
> +		ret = SDEI_INVALID_PARAMETERS;
> +		goto out;
> +	}
> +
> +	spin_lock(&vsdei->lock);
> +
> +	/* Check if the vcpu has been masked */
> +	if (vsdei->masked) {
> +		ret = SDEI_INVALID_PARAMETERS;
> +		goto unlock;
> +	}

You should still be able to signal an event if the vCPU is masked. Just
means the bit will rot in the pending bitmap until the vCPU is unmasked.

--
Thanks,
Oliver