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

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Date:   Mon, 2 May 2022 10:57:38 +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 06/18] KVM: arm64: Support SDEI_EVENT_CONTEXT hypercall

Hi Oliver,

On 4/30/22 11:03 PM, Oliver Upton wrote:
> 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.
>

Yep, the event's active state will be checked instead in next respin :)

Thanks,
Gavin