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Subject: Re: [PATCH v4 06/21] KVM: arm64: Support SDEI_EVENT_CONTEXT hypercall
To:     Gavin Shan <gshan@redhat.com>, kvmarm@lists.cs.columbia.edu
Cc:     maz@kernel.org, linux-kernel@vger.kernel.org,
        Jonathan.Cameron@huawei.com, pbonzini@redhat.com, will@kernel.org
References: <20210815001352.81927-1-gshan@redhat.com>
 <20210815001352.81927-7-gshan@redhat.com>
 <d9471e38-1840-1f79-c028-8f78afc0d2c7@redhat.com>
 <28219c6a-5200-b8f3-09e1-6aa08565030a@redhat.com>
From:   Eric Auger <eauger@redhat.com>
Message-ID: <33a1ba7a-ad97-00db-a381-3dbc88835e15@redhat.com>
Date:   Tue, 25 Jan 2022 19:29:12 +0100
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Hi Gavin,

On 1/12/22 3:33 AM, Gavin Shan wrote:
> Hi Eric,
> 
> On 11/10/21 7:16 PM, Eric Auger wrote:
>> On 8/15/21 2:13 AM, Gavin Shan wrote:
>>> This supports SDEI_EVENT_CONTEXT hypercall. It's used by the guest
>>> to retrieved the original registers (R0 - R17) in its SDEI event
>>> handler. Those registers can be corrupted during the SDEI event
>>> delivery.
>>>
>>> Signed-off-by: Gavin Shan <gshan@redhat.com>
>>> ---
>>>   arch/arm64/kvm/sdei.c | 40 ++++++++++++++++++++++++++++++++++++++++
>>>   1 file changed, 40 insertions(+)
>>>
>>> diff --git a/arch/arm64/kvm/sdei.c b/arch/arm64/kvm/sdei.c
>>> index b022ce0a202b..b4162efda470 100644
>>> --- a/arch/arm64/kvm/sdei.c
>>> +++ b/arch/arm64/kvm/sdei.c
>>> @@ -270,6 +270,44 @@ static unsigned long
>>> kvm_sdei_hypercall_enable(struct kvm_vcpu *vcpu,
>>>       return ret;
>>>   }
>>>   +static unsigned long kvm_sdei_hypercall_context(struct kvm_vcpu
>>> *vcpu)
>>> +{
>>> +    struct kvm *kvm = vcpu->kvm;
>>> +    struct kvm_sdei_kvm *ksdei = kvm->arch.sdei;
>>> +    struct kvm_sdei_vcpu *vsdei = vcpu->arch.sdei;
>>> +    struct kvm_sdei_vcpu_regs *regs;
>>> +    unsigned long index = smccc_get_arg1(vcpu);
>> s/index/param_id to match the spec?
> 
> Sure, but "reg_id" seems better here. As the parameter indicates the GPR
> index
> to be fetched on request of the guest kernel.
fine with me.
> 
>>> +    unsigned long ret = SDEI_SUCCESS;
>>> +
>>> +    /* Sanity check */
>>> +    if (!(ksdei && vsdei)) {
>>> +        ret = SDEI_NOT_SUPPORTED;
>>> +        goto out;
>>> +    }
>>> +
>>> +    if (index > ARRAY_SIZE(vsdei->state.critical_regs.regs)) {
>>> +        ret = SDEI_INVALID_PARAMETERS;
>>> +        goto out;
>>> +    }
>> I would move the above after regs = and use regs there (although the
>> regs ARRAY_SIZE of both is identifical)
> 
> Ok.
> 
>>> +
>>> +    /* Check if the pending event exists */
>>> +    spin_lock(&vsdei->lock);
>>> +    if (!(vsdei->critical_event || vsdei->normal_event)) {
>>> +        ret = SDEI_DENIED;
>>> +        goto unlock;
>>> +    }
>>> +
>>> +    /* Fetch the requested register */
>>> +    regs = vsdei->critical_event ? &vsdei->state.critical_regs :
>>> +                       &vsdei->state.normal_regs;
>>> +    ret = regs->regs[index];
>>> +
>>> +unlock:
>>> +    spin_unlock(&vsdei->lock);
>>> +out:
>>> +    return ret;
>>> +}
>>> +
>>>   int kvm_sdei_hypercall(struct kvm_vcpu *vcpu)
>>>   {
>>>       u32 func = smccc_get_function(vcpu);
>>> @@ -290,6 +328,8 @@ int kvm_sdei_hypercall(struct kvm_vcpu *vcpu)
>>>           ret = kvm_sdei_hypercall_enable(vcpu, false);
>>>           break;
>>>       case SDEI_1_0_FN_SDEI_EVENT_CONTEXT:
>>> +        ret = kvm_sdei_hypercall_context(vcpu);
>>> +        break;
>>>       case SDEI_1_0_FN_SDEI_EVENT_COMPLETE:
>>>       case SDEI_1_0_FN_SDEI_EVENT_COMPLETE_AND_RESUME:
>>>       case SDEI_1_0_FN_SDEI_EVENT_UNREGISTER:
>>>
> 
> Thanks,
> Gavin
> 
Eric