KVM: ARM: Power State Coordination Interface implementation

Implement the PSCI specification (ARM DEN 0022A) to control
virtual CPUs being "powered" on or off.

PSCI/KVM is detected using the KVM_CAP_ARM_PSCI capability.

A virtual CPU can now be initialized in a "powered off" state,
using the KVM_ARM_VCPU_POWER_OFF feature flag.

The guest can use either SMC or HVC to execute a PSCI function.

Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>

1 files changed, 108 insertions, 0 deletions

diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c
new file mode 100644
index 000000000000..7ee5bb7a3667
--- /dev/null
+++ b/arch/arm/kvm/psci.c
@@ -0,0 +1,108 @@
+/*
+ * Copyright (C) 2012 - ARM Ltd
+ * Author: Marc Zyngier <marc.zyngier@arm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/kvm_host.h>
+#include <linux/wait.h>
+
+#include <asm/kvm_emulate.h>
+#include <asm/kvm_psci.h>
+
+/*
+ * This is an implementation of the Power State Coordination Interface
+ * as described in ARM document number ARM DEN 0022A.
+ */
+
+static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu)
+{
+	vcpu->arch.pause = true;
+}
+
+static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
+{
+	struct kvm *kvm = source_vcpu->kvm;
+	struct kvm_vcpu *vcpu;
+	wait_queue_head_t *wq;
+	unsigned long cpu_id;
+	phys_addr_t target_pc;
+
+	cpu_id = *vcpu_reg(source_vcpu, 1);
+	if (vcpu_mode_is_32bit(source_vcpu))
+		cpu_id &= ~((u32) 0);
+
+	if (cpu_id >= atomic_read(&kvm->online_vcpus))
+		return KVM_PSCI_RET_INVAL;
+
+	target_pc = *vcpu_reg(source_vcpu, 2);
+
+	vcpu = kvm_get_vcpu(kvm, cpu_id);
+
+	wq = kvm_arch_vcpu_wq(vcpu);
+	if (!waitqueue_active(wq))
+		return KVM_PSCI_RET_INVAL;
+
+	kvm_reset_vcpu(vcpu);
+
+	/* Gracefully handle Thumb2 entry point */
+	if (vcpu_mode_is_32bit(vcpu) && (target_pc & 1)) {
+		target_pc &= ~((phys_addr_t) 1);
+		vcpu_set_thumb(vcpu);
+	}
+
+	*vcpu_pc(vcpu) = target_pc;
+	vcpu->arch.pause = false;
+	smp_mb();		/* Make sure the above is visible */
+
+	wake_up_interruptible(wq);
+
+	return KVM_PSCI_RET_SUCCESS;
+}
+
+/**
+ * kvm_psci_call - handle PSCI call if r0 value is in range
+ * @vcpu: Pointer to the VCPU struct
+ *
+ * Handle PSCI calls from guests through traps from HVC or SMC instructions.
+ * The calling convention is similar to SMC calls to the secure world where
+ * the function number is placed in r0 and this function returns true if the
+ * function number specified in r0 is withing the PSCI range, and false
+ * otherwise.
+ */
+bool kvm_psci_call(struct kvm_vcpu *vcpu)
+{
+	unsigned long psci_fn = *vcpu_reg(vcpu, 0) & ~((u32) 0);
+	unsigned long val;
+
+	switch (psci_fn) {
+	case KVM_PSCI_FN_CPU_OFF:
+		kvm_psci_vcpu_off(vcpu);
+		val = KVM_PSCI_RET_SUCCESS;
+		break;
+	case KVM_PSCI_FN_CPU_ON:
+		val = kvm_psci_vcpu_on(vcpu);
+		break;
+	case KVM_PSCI_FN_CPU_SUSPEND:
+	case KVM_PSCI_FN_MIGRATE:
+		val = KVM_PSCI_RET_NI;
+		break;
+
+	default:
+		return false;
+	}
+
+	*vcpu_reg(vcpu, 0) = val;
+	return true;
+}