diff mbox

[v7,11/12] ARM/ARM64: KVM: Emulate PSCI v0.2 CPU_SUSPEND

Message ID 1396435347-20056-12-git-send-email-anup.patel@linaro.org (mailing list archive)
State New, archived
Headers show

Commit Message

Anup Patel April 2, 2014, 10:42 a.m. UTC 
This patch adds emulation of PSCI v0.2 CPU_SUSPEND function call for
KVM ARM/ARM64. This is a CPU-level function call which can suspend
current CPU or current CPU cluster. We don't have VCPU clusters in
KVM so we only suspend the current VCPU.

The CPU_SUSPEND emulation is not tested much because currently there
is no CPUIDLE driver in Linux kernel that uses PSCI CPU_SUSPEND. The
PSCI CPU_SUSPEND implementation in ARM64 kernel was tested using a
Simple CPUIDLE driver which is not published due to unstable DT-bindings
for PSCI.
(For more info, http://lwn.net/Articles/574950/)

Even if we had stable DT-bindings for PSCI and CPUIDLE driver that
uses PSCI CPU_SUSPEND then still we need to define SUSPEND states
and WAKEUP events for KVM ARM/ARM64.

Due to above, we implement CPU_SUSPEND emulation similar to WFI
(Wait-for-interrupt) emulation and we also treat power-down request
to be same as stand-by request. This is also consistent with section
5.4.1 and section 5.4.2 of PSCI v0.2 specification.

Signed-off-by: Anup Patel <anup.patel@linaro.org>
Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@linaro.org>
---
 arch/arm/kvm/psci.c |   27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

Comments

Christoffer Dall April 2, 2014, 9:03 p.m. UTC | #1 
On Wed, Apr 02, 2014 at 04:12:26PM +0530, Anup Patel wrote:
> This patch adds emulation of PSCI v0.2 CPU_SUSPEND function call for
> KVM ARM/ARM64. This is a CPU-level function call which can suspend
> current CPU or current CPU cluster. We don't have VCPU clusters in
> KVM so we only suspend the current VCPU.
> 
> The CPU_SUSPEND emulation is not tested much because currently there
> is no CPUIDLE driver in Linux kernel that uses PSCI CPU_SUSPEND. The
> PSCI CPU_SUSPEND implementation in ARM64 kernel was tested using a
> Simple CPUIDLE driver which is not published due to unstable DT-bindings
> for PSCI.
> (For more info, http://lwn.net/Articles/574950/)
> 
> Even if we had stable DT-bindings for PSCI and CPUIDLE driver that
> uses PSCI CPU_SUSPEND then still we need to define SUSPEND states
> and WAKEUP events for KVM ARM/ARM64.
> 
> Due to above, we implement CPU_SUSPEND emulation similar to WFI
> (Wait-for-interrupt) emulation and we also treat power-down request
> to be same as stand-by request. This is also consistent with section
> 5.4.1 and section 5.4.2 of PSCI v0.2 specification.
> 
> Signed-off-by: Anup Patel <anup.patel@linaro.org>
> Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@linaro.org>
> ---
>  arch/arm/kvm/psci.c |   27 +++++++++++++++++++++++----
>  1 file changed, 23 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c
> index fdbd829..74fa4ad 100644
> --- a/arch/arm/kvm/psci.c
> +++ b/arch/arm/kvm/psci.c
> @@ -52,6 +52,25 @@ static unsigned long psci_affinity_mask(unsigned long affinity_level)
>  	return affinity_mask;
>  }
>  
> +static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu)
> +{
> +	/*
> +	 * NOTE: Currently, we don't have any wakeup events for KVM
> +	 * so for simplicity we make VCPU suspend emulation to be
> +	 * same-as WFI (Wait-for-interrupt) emulation. This is also
> +	 * consistent with intended use of StateID as described in
> +	 * section 5.4.1 of PSCI v0.2 specification (ARM DEN 0022A).

The WFI implementation wakes up on interrupts, so we are inherently
defining that as a wakeup event for KVM with this patch, so the comment
should be adjusted accordingly.

-Christoffer

> +	 *
> +	 * Further, we also treat power-down request to be same as
> +	 * stand-by request as-per section 5.4.2 clause 3 of PSCI v0.2
> +	 * specification (ARM DEN 0022A). This means all suspend states
> +	 * for KVM PSCI emulation will preserve the register state.
> +	 */
> +	kvm_vcpu_block(vcpu);
> +
> +	return PSCI_RET_SUCCESS;
> +}
> +
>  static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu)
>  {
>  	vcpu->arch.pause = true;
> @@ -195,6 +214,10 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
>  		 */
>  		val = 2;
>  		break;
> +	case PSCI_0_2_FN_CPU_SUSPEND:
> +	case PSCI_0_2_FN64_CPU_SUSPEND:
> +		val = kvm_psci_vcpu_suspend(vcpu);
> +		break;
>  	case PSCI_0_2_FN_CPU_OFF:
>  		kvm_psci_vcpu_off(vcpu);
>  		val = PSCI_RET_SUCCESS;
> @@ -232,10 +255,6 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
>  		val = PSCI_RET_SUCCESS;
>  		ret = 0;
>  		break;
> -	case PSCI_0_2_FN_CPU_SUSPEND:
> -	case PSCI_0_2_FN64_CPU_SUSPEND:
> -		val = PSCI_RET_NOT_SUPPORTED;
> -		break;
>  	default:
>  		return -EINVAL;
>  	}
> -- 
> 1.7.9.5
>
Anup Patel April 3, 2014, 5:28 a.m. UTC | #2 
On 3 April 2014 02:33, Christoffer Dall <christoffer.dall@linaro.org> wrote:
> On Wed, Apr 02, 2014 at 04:12:26PM +0530, Anup Patel wrote:
>> This patch adds emulation of PSCI v0.2 CPU_SUSPEND function call for
>> KVM ARM/ARM64. This is a CPU-level function call which can suspend
>> current CPU or current CPU cluster. We don't have VCPU clusters in
>> KVM so we only suspend the current VCPU.
>>
>> The CPU_SUSPEND emulation is not tested much because currently there
>> is no CPUIDLE driver in Linux kernel that uses PSCI CPU_SUSPEND. The
>> PSCI CPU_SUSPEND implementation in ARM64 kernel was tested using a
>> Simple CPUIDLE driver which is not published due to unstable DT-bindings
>> for PSCI.
>> (For more info, http://lwn.net/Articles/574950/)
>>
>> Even if we had stable DT-bindings for PSCI and CPUIDLE driver that
>> uses PSCI CPU_SUSPEND then still we need to define SUSPEND states
>> and WAKEUP events for KVM ARM/ARM64.
>>
>> Due to above, we implement CPU_SUSPEND emulation similar to WFI
>> (Wait-for-interrupt) emulation and we also treat power-down request
>> to be same as stand-by request. This is also consistent with section
>> 5.4.1 and section 5.4.2 of PSCI v0.2 specification.
>>
>> Signed-off-by: Anup Patel <anup.patel@linaro.org>
>> Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@linaro.org>
>> ---
>>  arch/arm/kvm/psci.c |   27 +++++++++++++++++++++++----
>>  1 file changed, 23 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c
>> index fdbd829..74fa4ad 100644
>> --- a/arch/arm/kvm/psci.c
>> +++ b/arch/arm/kvm/psci.c
>> @@ -52,6 +52,25 @@ static unsigned long psci_affinity_mask(unsigned long affinity_level)
>>       return affinity_mask;
>>  }
>>
>> +static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu)
>> +{
>> +     /*
>> +      * NOTE: Currently, we don't have any wakeup events for KVM
>> +      * so for simplicity we make VCPU suspend emulation to be
>> +      * same-as WFI (Wait-for-interrupt) emulation. This is also
>> +      * consistent with intended use of StateID as described in
>> +      * section 5.4.1 of PSCI v0.2 specification (ARM DEN 0022A).
>
> The WFI implementation wakes up on interrupts, so we are inherently
> defining that as a wakeup event for KVM with this patch, so the comment
> should be adjusted accordingly.

Sure, I will update the comment.

--
Anup

>
> -Christoffer
>
>> +      *
>> +      * Further, we also treat power-down request to be same as
>> +      * stand-by request as-per section 5.4.2 clause 3 of PSCI v0.2
>> +      * specification (ARM DEN 0022A). This means all suspend states
>> +      * for KVM PSCI emulation will preserve the register state.
>> +      */
>> +     kvm_vcpu_block(vcpu);
>> +
>> +     return PSCI_RET_SUCCESS;
>> +}
>> +
>>  static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu)
>>  {
>>       vcpu->arch.pause = true;
>> @@ -195,6 +214,10 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
>>                */
>>               val = 2;
>>               break;
>> +     case PSCI_0_2_FN_CPU_SUSPEND:
>> +     case PSCI_0_2_FN64_CPU_SUSPEND:
>> +             val = kvm_psci_vcpu_suspend(vcpu);
>> +             break;
>>       case PSCI_0_2_FN_CPU_OFF:
>>               kvm_psci_vcpu_off(vcpu);
>>               val = PSCI_RET_SUCCESS;
>> @@ -232,10 +255,6 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
>>               val = PSCI_RET_SUCCESS;
>>               ret = 0;
>>               break;
>> -     case PSCI_0_2_FN_CPU_SUSPEND:
>> -     case PSCI_0_2_FN64_CPU_SUSPEND:
>> -             val = PSCI_RET_NOT_SUPPORTED;
>> -             break;
>>       default:
>>               return -EINVAL;
>>       }
>> --
>> 1.7.9.5
>>
diff mbox

Patch

diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c
index fdbd829..74fa4ad 100644
--- a/arch/arm/kvm/psci.c
+++ b/arch/arm/kvm/psci.c
@@ -52,6 +52,25 @@  static unsigned long psci_affinity_mask(unsigned long affinity_level)
 	return affinity_mask;
 }
 
+static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu)
+{
+	/*
+	 * NOTE: Currently, we don't have any wakeup events for KVM
+	 * so for simplicity we make VCPU suspend emulation to be
+	 * same-as WFI (Wait-for-interrupt) emulation. This is also
+	 * consistent with intended use of StateID as described in
+	 * section 5.4.1 of PSCI v0.2 specification (ARM DEN 0022A).
+	 *
+	 * Further, we also treat power-down request to be same as
+	 * stand-by request as-per section 5.4.2 clause 3 of PSCI v0.2
+	 * specification (ARM DEN 0022A). This means all suspend states
+	 * for KVM PSCI emulation will preserve the register state.
+	 */
+	kvm_vcpu_block(vcpu);
+
+	return PSCI_RET_SUCCESS;
+}
+
 static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu)
 {
 	vcpu->arch.pause = true;
@@ -195,6 +214,10 @@  static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
 		 */
 		val = 2;
 		break;
+	case PSCI_0_2_FN_CPU_SUSPEND:
+	case PSCI_0_2_FN64_CPU_SUSPEND:
+		val = kvm_psci_vcpu_suspend(vcpu);
+		break;
 	case PSCI_0_2_FN_CPU_OFF:
 		kvm_psci_vcpu_off(vcpu);
 		val = PSCI_RET_SUCCESS;
@@ -232,10 +255,6 @@  static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
 		val = PSCI_RET_SUCCESS;
 		ret = 0;
 		break;
-	case PSCI_0_2_FN_CPU_SUSPEND:
-	case PSCI_0_2_FN64_CPU_SUSPEND:
-		val = PSCI_RET_NOT_SUPPORTED;
-		break;
 	default:
 		return -EINVAL;
 	}