[PATCH v2 06/11] KVM: arm64: Add support for SYSTEM_SUSPEND PSCI call

[Oliver Upton <oupton@google.com>]

ARM DEN0022D 5.19 "SYSTEM_SUSPEND" describes a PSCI call that may be
used to request a system be suspended. This is optional for PSCI v1.0
and to date KVM has elected to not implement the call. However, a
VMM/operator may wish to provide their guests with the ability to
suspend/resume, necessitating this PSCI call.

Implement support for SYSTEM_SUSPEND according to the prescribed
behavior in the specification. Add a new system event exit type,
KVM_SYSTEM_EVENT_SUSPEND, to notify userspace when a VM has requested a
system suspend. Make KVM_MP_STATE_HALTED a valid state on arm64.
Userspace can set this to request an in-kernel emulation of the suspend.

Signed-off-by: Oliver Upton <oupton@google.com>
---
 Documentation/virt/kvm/api.rst    |  6 ++++
 arch/arm64/include/asm/kvm_host.h |  3 ++
 arch/arm64/kvm/arm.c              |  8 +++++
 arch/arm64/kvm/psci.c             | 60 +++++++++++++++++++++++++++++++
 include/uapi/linux/kvm.h          |  2 ++
 5 files changed, 79 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index a6729c8cf063..361a57061b8f 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -5656,6 +5656,7 @@ should put the acknowledged interrupt vector into the 'epr' field.
   #define KVM_SYSTEM_EVENT_SHUTDOWN       1
   #define KVM_SYSTEM_EVENT_RESET          2
   #define KVM_SYSTEM_EVENT_CRASH          3
+  #define KVM_SYSTEM_EVENT_SUSPEND        4
 			__u32 type;
 			__u64 flags;
 		} system_event;
@@ -5680,6 +5681,11 @@ Valid values for 'type' are:
    has requested a crash condition maintenance. Userspace can choose
    to ignore the request, or to gather VM memory core dump and/or
    reset/shutdown of the VM.
+ - KVM_SYSTEM_EVENT_SUSPEND -- the guest has requested that the VM
+   suspends. Userspace is not obliged to honor this, and may call KVM_RUN
+   again. Doing so will cause the guest to resume at its requested entry
+   point. For ARM64, userspace can request in-kernel suspend emulation
+   by setting the vCPU's MP state to KVM_MP_STATE_HALTED.
 
 ::
 
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 1beda1189a15..441eb6fa7adc 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -137,6 +137,9 @@ struct kvm_arch {
 
 	/* Memory Tagging Extension enabled for the guest */
 	bool mte_enabled;
+
+	/* PSCI SYSTEM_SUSPEND call enabled for the guest */
+	bool suspend_enabled;
 };
 
 struct kvm_vcpu_fault_info {
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index f1a375648e25..d875d3bcf3c5 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -101,6 +101,10 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
 		}
 		mutex_unlock(&kvm->lock);
 		break;
+	case KVM_CAP_ARM_SYSTEM_SUSPEND:
+		r = 0;
+		kvm->arch.suspend_enabled = true;
+		break;
 	default:
 		r = -EINVAL;
 		break;
@@ -215,6 +219,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_SET_GUEST_DEBUG:
 	case KVM_CAP_VCPU_ATTRIBUTES:
 	case KVM_CAP_PTP_KVM:
+	case KVM_CAP_ARM_SYSTEM_SUSPEND:
 		r = 1;
 		break;
 	case KVM_CAP_SET_GUEST_DEBUG2:
@@ -470,6 +475,9 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
 	int ret = 0;
 
 	switch (mp_state->mp_state) {
+	case KVM_MP_STATE_HALTED:
+		kvm_make_request(KVM_REQ_SUSPEND, vcpu);
+		fallthrough;
 	case KVM_MP_STATE_RUNNABLE:
 		vcpu->arch.power_off = false;
 		break;
diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
index d453666ddb83..cf869f1f8615 100644
--- a/arch/arm64/kvm/psci.c
+++ b/arch/arm64/kvm/psci.c
@@ -203,6 +203,46 @@ static void kvm_psci_system_reset(struct kvm_vcpu *vcpu)
 	kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_RESET);
 }
 
+static int kvm_psci_system_suspend(struct kvm_vcpu *vcpu)
+{
+	unsigned long entry_addr, context_id;
+	struct kvm *kvm = vcpu->kvm;
+	unsigned long psci_ret = 0;
+	struct kvm_vcpu *tmp;
+	int ret = 0;
+	int i;
+
+	/*
+	 * The SYSTEM_SUSPEND PSCI call requires that all vCPUs (except the
+	 * calling vCPU) be in an OFF state, as determined by the
+	 * implementation.
+	 *
+	 * See ARM DEN0022D, 5.19 "SYSTEM_SUSPEND" for more details.
+	 */
+	mutex_lock(&kvm->lock);
+	kvm_for_each_vcpu(i, tmp, kvm) {
+		if (tmp != vcpu && !tmp->arch.power_off) {
+			psci_ret = PSCI_RET_DENIED;
+			ret = 1;
+			goto out;
+		}
+	}
+
+	entry_addr = smccc_get_arg1(vcpu);
+	context_id = smccc_get_arg2(vcpu);
+
+	kvm_psci_vcpu_request_reset(vcpu, entry_addr, context_id,
+				    kvm_vcpu_is_be(vcpu));
+
+	memset(&vcpu->run->system_event, 0, sizeof(vcpu->run->system_event));
+	vcpu->run->system_event.type = KVM_SYSTEM_EVENT_SUSPEND;
+	vcpu->run->exit_reason = KVM_EXIT_SYSTEM_EVENT;
+out:
+	mutex_unlock(&kvm->lock);
+	smccc_set_retval(vcpu, psci_ret, 0, 0, 0);
+	return ret;
+}
+
 static void kvm_psci_narrow_to_32bit(struct kvm_vcpu *vcpu)
 {
 	int i;
@@ -223,6 +263,14 @@ static unsigned long kvm_psci_check_allowed_function(struct kvm_vcpu *vcpu, u32
 	if ((fn & PSCI_0_2_64BIT) && vcpu_mode_is_32bit(vcpu))
 		return PSCI_RET_NOT_SUPPORTED;
 
+	switch (fn) {
+	case PSCI_1_0_FN_SYSTEM_SUSPEND:
+	case PSCI_1_0_FN64_SYSTEM_SUSPEND:
+		if (!vcpu->kvm->arch.suspend_enabled)
+			return PSCI_RET_NOT_SUPPORTED;
+		break;
+	}
+
 	return 0;
 }
 
@@ -316,6 +364,10 @@ static int kvm_psci_1_0_call(struct kvm_vcpu *vcpu)
 	unsigned long val;
 	int ret = 1;
 
+	val = kvm_psci_check_allowed_function(vcpu, psci_fn);
+	if (val)
+		goto out;
+
 	switch(psci_fn) {
 	case PSCI_0_2_FN_PSCI_VERSION:
 		val = KVM_ARM_PSCI_1_0;
@@ -339,6 +391,8 @@ static int kvm_psci_1_0_call(struct kvm_vcpu *vcpu)
 		case PSCI_0_2_FN_SYSTEM_OFF:
 		case PSCI_0_2_FN_SYSTEM_RESET:
 		case PSCI_1_0_FN_PSCI_FEATURES:
+		case PSCI_1_0_FN_SYSTEM_SUSPEND:
+		case PSCI_1_0_FN64_SYSTEM_SUSPEND:
 		case ARM_SMCCC_VERSION_FUNC_ID:
 			val = 0;
 			break;
@@ -347,10 +401,16 @@ static int kvm_psci_1_0_call(struct kvm_vcpu *vcpu)
 			break;
 		}
 		break;
+	case PSCI_1_0_FN_SYSTEM_SUSPEND:
+		kvm_psci_narrow_to_32bit(vcpu);
+		fallthrough;
+	case PSCI_1_0_FN64_SYSTEM_SUSPEND:
+		return kvm_psci_system_suspend(vcpu);
 	default:
 		return kvm_psci_0_2_call(vcpu);
 	}
 
+out:
 	smccc_set_retval(vcpu, val, 0, 0, 0);
 	return ret;
 }
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index a067410ebea5..052b0e717b08 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -433,6 +433,7 @@ struct kvm_run {
 #define KVM_SYSTEM_EVENT_SHUTDOWN       1
 #define KVM_SYSTEM_EVENT_RESET          2
 #define KVM_SYSTEM_EVENT_CRASH          3
+#define KVM_SYSTEM_EVENT_SUSPEND        4
 			__u32 type;
 			__u64 flags;
 		} system_event;
@@ -1112,6 +1113,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_BINARY_STATS_FD 203
 #define KVM_CAP_EXIT_ON_EMULATION_FAILURE 204
 #define KVM_CAP_ARM_MTE 205
+#define KVM_CAP_ARM_SYSTEM_SUSPEND 206
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
-- 
2.33.0.685.g46640cef36-goog