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

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Date:   Mon, 2 May 2022 11:04:44 +0800
From:   Gavin Shan <gshan@...hat.com>
To:     Oliver Upton <oupton@...gle.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 Oliver,

On 5/1/22 5:32 AM, Oliver Upton wrote:
> 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.
> 

Nice point! The event pending state is set if vCPU is masked. However,
it's not becoming active until the vCPU is unmasked :)

Thanks,
Gavin