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Commit b376d02b authored by Anup Patel's avatar Anup Patel Committed by Christoffer Dall
Browse files

ARM/ARM64: KVM: Emulate PSCI v0.2 CPU_SUSPEND 

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/

)

For simplicity, 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 consistent with section
5.4.1 and section 5.4.2 of PSCI v0.2 specification.

Signed-off-by: default avatarAnup Patel <anup.patel@linaro.org>
Signed-off-by: default avatarPranavkumar Sawargaonkar <pranavkumar@linaro.org>
Acked-by: default avatarChristoffer Dall <christoffer.dall@linaro.org>
Acked-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarChristoffer Dall <christoffer.dall@linaro.org>
parent aa8aeefe

arch/arm/kvm/psci.c

+24 −4
Original line number Diff line number Diff line
@@ -37,6 +37,26 @@ static unsigned long psci_affinity_mask(unsigned long affinity_level) 
	return 0;

}



static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu)

{

	/*

	 * NOTE: For simplicity, we make VCPU suspend emulation to be

	 * same-as WFI (Wait-for-interrupt) emulation.

	 *

	 * This means for KVM the wakeup events are interrupts and

	 * this is 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 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;
@@ -183,6 +203,10 @@ 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;
@@ -235,10 +259,6 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu) 
		val = PSCI_RET_INTERNAL_FAILURE;

		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;

	}