Implement virtual timer for secondary VMs.
If the timer fires while the secondary VM is running, the physical
interrupt will go to the primary VM, which should then run the secondary
again. Hafnium will then inject the virtual timer interrupt
automatically, and mask the timer interrupt so it doesn't immediately go
back to the primary. Note that the secondary must clear this mask before
it can get another timer interrupt.
Bug: 117271574
Change-Id: If90a3c4fd133333713ad6bf7d6a3b515ae6fea6a
diff --git a/inc/hf/arch/timer.h b/inc/hf/arch/timer.h
new file mode 100644
index 0000000..935a9f4
--- /dev/null
+++ b/inc/hf/arch/timer.h
@@ -0,0 +1,72 @@
+/*
+ * Copyright 2018 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include "hf/arch/types.h"
+
+/**
+ * Sets the bit to mask virtual timer interrupts.
+ */
+void arch_timer_mask(struct arch_regs *regs);
+
+/**
+ * Checks whether the virtual timer is enabled and its interrupt not masked.
+ */
+bool arch_timer_enabled(struct arch_regs *regs);
+
+/**
+ * Returns the number of ticks remaining on the virtual timer as stored in
+ * the given `arch_regs`, or 0 if it has already expired. This is undefined if
+ * the timer is not enabled.
+ */
+uint64_t arch_timer_remaining_ticks(struct arch_regs *regs);
+
+/**
+ * Returns the number of nanoseconds remaining on the virtual timer as stored in
+ * the given `arch_regs`, or 0 if it has already expired. This is undefined if
+ * the timer is not enabled.
+ */
+uint64_t arch_timer_remaining_ns(struct arch_regs *regs);
+
+/**
+ * Returns whether the timer is ready to fire: i.e. it is enabled, not masked,
+ * and the condition is met.
+ */
+bool arch_timer_pending(struct arch_regs *regs);
+
+/**
+ * Checks whether the virtual timer is enabled and its interrupt not masked, for
+ * the currently active vCPU.
+ */
+bool arch_timer_enabled_current(void);
+
+/**
+ * Returns the number of ticks remaining on the virtual timer of the currently
+ * active vCPU, or 0 if it has already expired. This is undefined if the timer
+ * is not enabled.
+ */
+uint64_t arch_timer_remaining_ticks_current(void);
+
+/**
+ * Returns the number of nanoseconds remaining on the virtual timer of the
+ * currently active vCPU, or 0 if it has already expired. This is undefined if
+ * the timer is not enabled.
+ */
+uint64_t arch_timer_remaining_ns_current(void);