[v8] arm64: Support for Arm CCA in KVM

[PATCH v8 21/43] KVM: arm64: Handle realm VCPU load

Posted by Steven Price 8 months ago

When loading a realm VCPU much of the work is handled by the RMM so only
some of the actions are required. Rearrange kvm_arch_vcpu_load()
slightly so we can bail out early for a realm guest.

Signed-off-by: Steven Price <steven.price@arm.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
---
 arch/arm64/kvm/arm.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index cf707130ef66..08d5e0d76749 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -644,10 +644,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 	kvm_timer_vcpu_load(vcpu);
 	kvm_vgic_load(vcpu);
 	kvm_vcpu_load_debug(vcpu);
-	if (has_vhe())
-		kvm_vcpu_load_vhe(vcpu);
-	kvm_arch_vcpu_load_fp(vcpu);
-	kvm_vcpu_pmu_restore_guest(vcpu);
 	if (kvm_arm_is_pvtime_enabled(&vcpu->arch))
 		kvm_make_request(KVM_REQ_RECORD_STEAL, vcpu);
 
@@ -671,6 +667,15 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 			     &vcpu->arch.vgic_cpu.vgic_v3);
 	}
 
+	/* No additional state needs to be loaded on Realmed VMs */
+	if (vcpu_is_rec(vcpu))
+		return;
+
+	if (has_vhe())
+		kvm_vcpu_load_vhe(vcpu);
+	kvm_arch_vcpu_load_fp(vcpu);
+	kvm_vcpu_pmu_restore_guest(vcpu);
+
 	if (!cpumask_test_cpu(cpu, vcpu->kvm->arch.supported_cpus))
 		vcpu_set_on_unsupported_cpu(vcpu);
 }
-- 
2.43.0

Re: [PATCH v8 21/43] KVM: arm64: Handle realm VCPU load

Posted by Suzuki K Poulose 7 months ago

On 16/04/2025 14:41, Steven Price wrote:
> When loading a realm VCPU much of the work is handled by the RMM so only
> some of the actions are required. Rearrange kvm_arch_vcpu_load()
> slightly so we can bail out early for a realm guest.
> 
> Signed-off-by: Steven Price <steven.price@arm.com>
> Reviewed-by: Gavin Shan <gshan@redhat.com>
> ---
>   arch/arm64/kvm/arm.c | 13 +++++++++----
>   1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index cf707130ef66..08d5e0d76749 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -644,10 +644,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)

I think we use the pkvm hook to skip to the nommu goto, to avoid
the VMID allocation and context flush.


>   	kvm_timer_vcpu_load(vcpu);
>   	kvm_vgic_load(vcpu);
>   	kvm_vcpu_load_debug(vcpu);
> -	if (has_vhe())
> -		kvm_vcpu_load_vhe(vcpu);
> -	kvm_arch_vcpu_load_fp(vcpu);
> -	kvm_vcpu_pmu_restore_guest(vcpu);
>   	if (kvm_arm_is_pvtime_enabled(&vcpu->arch))
>   		kvm_make_request(KVM_REQ_RECORD_STEAL, vcpu);

We could also move thise pvtime to the bottom too ?

>   
> @@ -671,6 +667,15 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>   			     &vcpu->arch.vgic_cpu.vgic_v3);
>   	}
>   
> +	/* No additional state needs to be loaded on Realmed VMs */
> +	if (vcpu_is_rec(vcpu))
> +		return;
> +
> +	if (has_vhe())
> +		kvm_vcpu_load_vhe(vcpu);
> +	kvm_arch_vcpu_load_fp(vcpu);
> +	kvm_vcpu_pmu_restore_guest(vcpu);
> +

With the above addressed:

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>


>   	if (!cpumask_test_cpu(cpu, vcpu->kvm->arch.supported_cpus))
>   		vcpu_set_on_unsupported_cpu(vcpu);
>   }

Re: [PATCH v8 21/43] KVM: arm64: Handle realm VCPU load

Posted by Steven Price 6 months, 4 weeks ago

On 19/05/2025 18:48, Suzuki K Poulose wrote:
> On 16/04/2025 14:41, Steven Price wrote:
>> When loading a realm VCPU much of the work is handled by the RMM so only
>> some of the actions are required. Rearrange kvm_arch_vcpu_load()
>> slightly so we can bail out early for a realm guest.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> Reviewed-by: Gavin Shan <gshan@redhat.com>
>> ---
>>   arch/arm64/kvm/arm.c | 13 +++++++++----
>>   1 file changed, 9 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
>> index cf707130ef66..08d5e0d76749 100644
>> --- a/arch/arm64/kvm/arm.c
>> +++ b/arch/arm64/kvm/arm.c
>> @@ -644,10 +644,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu,
>> int cpu)
> 
> I think we use the pkvm hook to skip to the nommu goto, to avoid
> the VMID allocation and context flush.
> 
> 
>>       kvm_timer_vcpu_load(vcpu);
>>       kvm_vgic_load(vcpu);
>>       kvm_vcpu_load_debug(vcpu);
>> -    if (has_vhe())
>> -        kvm_vcpu_load_vhe(vcpu);
>> -    kvm_arch_vcpu_load_fp(vcpu);
>> -    kvm_vcpu_pmu_restore_guest(vcpu);
>>       if (kvm_arm_is_pvtime_enabled(&vcpu->arch))
>>           kvm_make_request(KVM_REQ_RECORD_STEAL, vcpu);
> 
> We could also move thise pvtime to the bottom too ?
> 
>>   @@ -671,6 +667,15 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu,
>> int cpu)
>>                    &vcpu->arch.vgic_cpu.vgic_v3);
>>       }
>>   +    /* No additional state needs to be loaded on Realmed VMs */
>> +    if (vcpu_is_rec(vcpu))
>> +        return;
>> +
>> +    if (has_vhe())
>> +        kvm_vcpu_load_vhe(vcpu);
>> +    kvm_arch_vcpu_load_fp(vcpu);
>> +    kvm_vcpu_pmu_restore_guest(vcpu);
>> +
> 
> With the above addressed:
> 
> Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>

Thanks, the suggestions above seem sensible, I'll make those changes.

Thanks,
Steve

> 
> 
>>       if (!cpumask_test_cpu(cpu, vcpu->kvm->arch.supported_cpus))
>>           vcpu_set_on_unsupported_cpu(vcpu);
>>   }
>