linux-kernel - [PATCH kvmtool v4 11/15] arm64: psci: Implement CPU

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Message-ID: <20250930103130.197534-13-suzuki.poulose@arm.com>
Date: Tue, 30 Sep 2025 11:31:26 +0100
From: Suzuki K Poulose <suzuki.poulose@....com>
To: kvmarm@...ts.linux.dev
Cc: kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	will@...nel.org,
	oliver.upton@...ux.dev,
	maz@...nel.org,
	alexandru.elisei@....com,
	aneesh.kumar@...nel.org,
	steven.price@....com,
	tabba@...gle.com,
	Suzuki K Poulose <suzuki.poulose@....com>
Subject: [PATCH kvmtool v4 11/15] arm64: psci: Implement CPU_ON

From: Oliver Upton <oliver.upton@...ux.dev>

Add support for the PSCI CPU_ON call, wherein a caller can power on a
targeted CPU and reset it with the provided context (i.e. entrypoint and
context id). Rely on the KVM_ARM_VCPU_INIT ioctl, which has the effect
of an architectural warm reset, to do the heavy lifting.

Signed-off-by: Oliver Upton <oliver.upton@...ux.dev>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
---
 arm64/psci.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/arm64/psci.c b/arm64/psci.c
index 72429b36..14c98639 100644
--- a/arm64/psci.c
+++ b/arm64/psci.c
@@ -18,6 +18,8 @@ static void psci_features(struct kvm_cpu *vcpu, struct arm_smccc_res *res)
 	case PSCI_0_2_FN_CPU_SUSPEND:
 	case PSCI_0_2_FN64_CPU_SUSPEND:
 	case PSCI_0_2_FN_CPU_OFF:
+	case PSCI_0_2_FN_CPU_ON:
+	case PSCI_0_2_FN64_CPU_ON:
 	case ARM_SMCCC_VERSION_FUNC_ID:
 		res->a0 = PSCI_RET_SUCCESS;
 		break;
@@ -47,6 +49,68 @@ static void cpu_off(struct kvm_cpu *vcpu, struct arm_smccc_res *res)
 		die_perror("KVM_SET_MP_STATE failed");
 }
 
+static void reset_cpu_with_context(struct kvm_cpu *vcpu, u64 entry_addr, u64 ctx_id)
+{
+	struct kvm_one_reg reg;
+
+	if (ioctl(vcpu->vcpu_fd, KVM_ARM_VCPU_INIT, &vcpu->init))
+		die_perror("KVM_ARM_VCPU_INIT failed");
+
+	reg = (struct kvm_one_reg) {
+		.id	= ARM64_CORE_REG(regs.pc),
+		.addr	= (u64)&entry_addr,
+	};
+	if (ioctl(vcpu->vcpu_fd, KVM_SET_ONE_REG, &reg))
+		die_perror("KVM_SET_ONE_REG failed");
+
+	reg = (struct kvm_one_reg) {
+		.id	= ARM64_CORE_REG(regs.regs[0]),
+		.addr	= (u64)&ctx_id,
+	};
+	if (ioctl(vcpu->vcpu_fd, KVM_SET_ONE_REG, &reg))
+		die_perror("KVM_SET_ONE_REG failed");
+}
+
+static bool psci_valid_affinity(u64 affinity)
+{
+	return !(affinity & ~ARM_MPIDR_HWID_BITMASK);
+}
+
+static void cpu_on(struct kvm_cpu *vcpu, struct arm_smccc_res *res)
+{
+	u64 target_mpidr = smccc_get_arg(vcpu, 1);
+	u64 entry_addr = smccc_get_arg(vcpu, 2);
+	u64 ctx_id = smccc_get_arg(vcpu, 3);
+	struct kvm_mp_state mp_state;
+	struct kvm_cpu *target;
+
+	if (!psci_valid_affinity(target_mpidr)) {
+		res->a0 = PSCI_RET_INVALID_PARAMS;
+		return;
+	}
+
+	kvm__pause(vcpu->kvm);
+
+	target = kvm__arch_mpidr_to_vcpu(vcpu->kvm, target_mpidr);
+	if (!target) {
+		res->a0 = PSCI_RET_INVALID_PARAMS;
+		goto out_continue;
+	}
+
+	if (ioctl(target->vcpu_fd, KVM_GET_MP_STATE, &mp_state))
+		die_perror("KVM_GET_MP_STATE failed");
+
+	if (mp_state.mp_state != KVM_MP_STATE_STOPPED) {
+		res->a0 = PSCI_RET_ALREADY_ON;
+		goto out_continue;
+	}
+
+	reset_cpu_with_context(target, entry_addr, ctx_id);
+	res->a0 = PSCI_RET_SUCCESS;
+out_continue:
+	kvm__continue(vcpu->kvm);
+}
+
 void handle_psci(struct kvm_cpu *vcpu, struct arm_smccc_res *res)
 {
 	switch (vcpu->kvm_run->hypercall.nr) {
@@ -63,6 +127,10 @@ void handle_psci(struct kvm_cpu *vcpu, struct arm_smccc_res *res)
 	case PSCI_0_2_FN_CPU_OFF:
 		cpu_off(vcpu, res);
 		break;
+	case PSCI_0_2_FN_CPU_ON:
+	case PSCI_0_2_FN64_CPU_ON:
+		cpu_on(vcpu, res);
+		break;
 	default:
 		res->a0 = PSCI_RET_NOT_SUPPORTED;
 	}
-- 
2.43.0