[PATCH v9 07/12] ARM/ARM64: KVM: Emulate PSCI v0.2 SYSTEM_OFF and SYSTEM_RESET

[Anup Patel]

On Tue, Apr 15, 2014 at 4:04 PM, Marc Zyngier <marc.zyngier at arm.com> wrote:
> On Tue, Apr 15 2014 at  7:14:10 am BST, Anup Patel <anup.patel at linaro.org> wrote:
>> The PSCI v0.2 SYSTEM_OFF and SYSTEM_RESET functions are system-level
>> functions hence cannot be fully emulated by in-kernel PSCI emulation code.
>>
>> To tackle this, we forward PSCI v0.2 SYSTEM_OFF and SYSTEM_RESET function
>> calls from vcpu to user space (i.e. QEMU or KVMTOOL) via kvm_run structure
>> using KVM_EXIT_SYSTEM_EVENT exit reasons.
>>
>> Signed-off-by: Anup Patel <anup.patel at linaro.org>
>> Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar at linaro.org>
>> Reviewed-by: Christoffer Dall <christoffer.dall at linaro.org>
>> ---
>>  arch/arm/kvm/psci.c |   32 +++++++++++++++++++++++++++++---
>>  1 file changed, 29 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c
>> index 14e6fa6..b964aa4 100644
>> --- a/arch/arm/kvm/psci.c
>> +++ b/arch/arm/kvm/psci.c
>> @@ -85,6 +85,23 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
>>       return PSCI_RET_SUCCESS;
>>  }
>>
>> +static inline void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type)
>
> Loose the "inline". This is not performance critical, and the compiler
> does a pretty good job doing that for you.

OK, I will drop the "inline" attribute.

>
>> +{
>> +     memset(&vcpu->run->system_event, 0, sizeof(vcpu->run->system_event));
>> +     vcpu->run->system_event.type = type;
>> +     vcpu->run->exit_reason = KVM_EXIT_SYSTEM_EVENT;
>> +}
>> +
>> +static void kvm_psci_system_off(struct kvm_vcpu *vcpu)
>> +{
>> +     kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_SHUTDOWN);
>> +}
>> +
>> +static void kvm_psci_system_reset(struct kvm_vcpu *vcpu)
>> +{
>> +     kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_RESET);
>> +}
>> +
>>  int kvm_psci_version(struct kvm_vcpu *vcpu)
>>  {
>>       if (test_bit(KVM_ARM_VCPU_PSCI_0_2, vcpu->arch.features))
>> @@ -95,6 +112,7 @@ int kvm_psci_version(struct kvm_vcpu *vcpu)
>>
>>  static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
>>  {
>> +     int ret = 1;
>>       unsigned long psci_fn = *vcpu_reg(vcpu, 0) & ~((u32) 0);
>>       unsigned long val;
>>
>> @@ -114,13 +132,21 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
>>       case PSCI_0_2_FN64_CPU_ON:
>>               val = kvm_psci_vcpu_on(vcpu);
>>               break;
>> +     case PSCI_0_2_FN_SYSTEM_OFF:
>> +             kvm_psci_system_off(vcpu);
>> +             val = PSCI_RET_SUCCESS;
>> +             ret = 0;
>> +             break;
>> +     case PSCI_0_2_FN_SYSTEM_RESET:
>> +             kvm_psci_system_reset(vcpu);
>> +             val = PSCI_RET_SUCCESS;
>> +             ret = 0;
>> +             break;
>
> What is the significance of setting val to PSCI_RET_SUCCESS here? We're
> exiting to userspace, so surely only the platform emulation can set
> that. Am I missing something?

Actually, return value is undefined for SYSTEM_OFF and SYSTEM_RESET
because these functions are not expected to return. Currently, we are updating
r0 (or x0) for all PSCI functions.

Are you suggesting that we update r0 (or x0) only when there are no error
(i.e. ret == 0) ?

>
>>       case PSCI_0_2_FN_CPU_SUSPEND:
>>       case PSCI_0_2_FN_AFFINITY_INFO:
>>       case PSCI_0_2_FN_MIGRATE:
>>       case PSCI_0_2_FN_MIGRATE_INFO_TYPE:
>>       case PSCI_0_2_FN_MIGRATE_INFO_UP_CPU:
>> -     case PSCI_0_2_FN_SYSTEM_OFF:
>> -     case PSCI_0_2_FN_SYSTEM_RESET:
>>       case PSCI_0_2_FN64_CPU_SUSPEND:
>>       case PSCI_0_2_FN64_AFFINITY_INFO:
>>       case PSCI_0_2_FN64_MIGRATE:
>> @@ -132,7 +158,7 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
>>       }
>>
>>       *vcpu_reg(vcpu, 0) = val;
>> -     return 1;
>> +     return ret;
>>  }
>>
>>  static int kvm_psci_0_1_call(struct kvm_vcpu *vcpu)
> --
> Jazz is not dead. It just smells funny.
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--
Anup