The RMM keeps track of the timer while the realm REC is running, but on
exit to the normal world KVM is responsible for handling the timers.

A later patch adds the support for propagating the timer values from the
exit data structure and calling kvm_realm_timers_update().

Signed-off-by: Steven Price <steven.price@arm.com>
---
Changes since v11:
 * Drop the kvm_is_realm() check from timer_set_offset(). We already
   ensure that the offset is 0 when calling the function.
Changes since v10:
 * KVM_CAP_COUNTER_OFFSET is now already hidden by a previous patch.
Changes since v9:
 * No need to move the call to kvm_timer_unblocking() in
   kvm_timer_vcpu_load().
Changes since v7:
 * Hide KVM_CAP_COUNTER_OFFSET for realm guests.
---
 arch/arm64/kvm/arch_timer.c  | 37 ++++++++++++++++++++++++++++++++++--
 include/kvm/arm_arch_timer.h |  2 ++
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c
index 99a07972068d..99308bde2a05 100644
--- a/arch/arm64/kvm/arch_timer.c
+++ b/arch/arm64/kvm/arch_timer.c
@@ -453,6 +453,21 @@ static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level,
 			    timer_ctx);
 }
 
+void kvm_realm_timers_update(struct kvm_vcpu *vcpu)
+{
+	struct arch_timer_cpu *arch_timer = &vcpu->arch.timer_cpu;
+	int i;
+
+	for (i = 0; i < NR_KVM_EL0_TIMERS; i++) {
+		struct arch_timer_context *timer = &arch_timer->timers[i];
+		bool status = timer_get_ctl(timer) & ARCH_TIMER_CTRL_IT_STAT;
+		bool level = kvm_timer_irq_can_fire(timer) && status;
+
+		if (level != timer->irq.level)
+			kvm_timer_update_irq(vcpu, level, timer);
+	}
+}
+
 /* Only called for a fully emulated timer */
 static void timer_emulate(struct arch_timer_context *ctx)
 {
@@ -1056,7 +1071,9 @@ static void timer_context_init(struct kvm_vcpu *vcpu, int timerid)
 
 	ctxt->timer_id = timerid;
 
-	if (timerid == TIMER_VTIMER)
+	if (kvm_is_realm(vcpu->kvm))
+		ctxt->offset.vm_offset = NULL;
+	else if (timerid == TIMER_VTIMER)
 		ctxt->offset.vm_offset = &kvm->arch.timer_data.voffset;
 	else
 		ctxt->offset.vm_offset = &kvm->arch.timer_data.poffset;
@@ -1078,13 +1095,19 @@ static void timer_context_init(struct kvm_vcpu *vcpu, int timerid)
 void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu)
 {
 	struct arch_timer_cpu *timer = vcpu_timer(vcpu);
+	u64 cntvoff;
 
 	for (int i = 0; i < NR_KVM_TIMERS; i++)
 		timer_context_init(vcpu, i);
 
+	if (kvm_is_realm(vcpu->kvm))
+		cntvoff = 0;
+	else
+		cntvoff = kvm_phys_timer_read();
+
 	/* Synchronize offsets across timers of a VM if not already provided */
 	if (!test_bit(KVM_ARCH_FLAG_VM_COUNTER_OFFSET, &vcpu->kvm->arch.flags)) {
-		timer_set_offset(vcpu_vtimer(vcpu), kvm_phys_timer_read());
+		timer_set_offset(vcpu_vtimer(vcpu), cntvoff);
 		timer_set_offset(vcpu_ptimer(vcpu), 0);
 	}
 
@@ -1556,6 +1579,13 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu)
 		return -EINVAL;
 	}
 
+	/*
+	 * We don't use mapped IRQs for Realms because the RMI doesn't allow
+	 * us setting the LR.HW bit in the VGIC.
+	 */
+	if (vcpu_is_rec(vcpu))
+		return 0;
+
 	get_timer_map(vcpu, &map);
 
 	ret = kvm_vgic_map_phys_irq(vcpu,
@@ -1687,6 +1717,9 @@ int kvm_vm_ioctl_set_counter_offset(struct kvm *kvm,
 	if (offset->reserved)
 		return -EINVAL;
 
+	if (kvm_is_realm(kvm))
+		return -EINVAL;
+
 	mutex_lock(&kvm->lock);
 
 	if (!kvm_trylock_all_vcpus(kvm)) {
diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h
index 7310841f4512..bab0daafc6b1 100644
--- a/include/kvm/arm_arch_timer.h
+++ b/include/kvm/arm_arch_timer.h
@@ -111,6 +111,8 @@ int kvm_arm_timer_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr);
 int kvm_arm_timer_get_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr);
 int kvm_arm_timer_has_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr);
 
+void kvm_realm_timers_update(struct kvm_vcpu *vcpu);
+
 u64 kvm_phys_timer_read(void);
 
 void kvm_timer_vcpu_load(struct kvm_vcpu *vcpu);
-- 
2.43.0