KVM: arm64: selftests: Add basic support for arch_timers

Add a minimalistic library support to access the virtual timers,
that can be used for simple timing functionalities, such as
introducing delays in the guest.
Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211007233439.1826892-7-rananta@google.com

tools/testing/selftests/kvm/include/aarch64/arch_timer.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * ARM Generic Timer specific interface
+ */
+
+#ifndef SELFTEST_KVM_ARCH_TIMER_H
+#define SELFTEST_KVM_ARCH_TIMER_H
+
+#include "processor.h"
+
+enum arch_timer {
+	VIRTUAL,
+	PHYSICAL,
+};
+
+#define CTL_ENABLE	(1 << 0)
+#define CTL_IMASK	(1 << 1)
+#define CTL_ISTATUS	(1 << 2)
+
+#define msec_to_cycles(msec)	\
+	(timer_get_cntfrq() * (uint64_t)(msec) / 1000)
+
+#define usec_to_cycles(usec)	\
+	(timer_get_cntfrq() * (uint64_t)(usec) / 1000000)
+
+#define cycles_to_usec(cycles) \
+	((uint64_t)(cycles) * 1000000 / timer_get_cntfrq())
+
+static inline uint32_t timer_get_cntfrq(void)
+{
+	return read_sysreg(cntfrq_el0);
+}
+
+static inline uint64_t timer_get_cntct(enum arch_timer timer)
+{
+	isb();
+
+	switch (timer) {
+	case VIRTUAL:
+		return read_sysreg(cntvct_el0);
+	case PHYSICAL:
+		return read_sysreg(cntpct_el0);
+	default:
+		GUEST_ASSERT_1(0, timer);
+	}
+
+	/* We should not reach here */
+	return 0;
+}
+
+static inline void timer_set_cval(enum arch_timer timer, uint64_t cval)
+{
+	switch (timer) {
+	case VIRTUAL:
+		write_sysreg(cval, cntv_cval_el0);
+		break;
+	case PHYSICAL:
+		write_sysreg(cval, cntp_cval_el0);
+		break;
+	default:
+		GUEST_ASSERT_1(0, timer);
+	}
+
+	isb();
+}
+
+static inline uint64_t timer_get_cval(enum arch_timer timer)
+{
+	switch (timer) {
+	case VIRTUAL:
+		return read_sysreg(cntv_cval_el0);
+	case PHYSICAL:
+		return read_sysreg(cntp_cval_el0);
+	default:
+		GUEST_ASSERT_1(0, timer);
+	}
+
+	/* We should not reach here */
+	return 0;
+}
+
+static inline void timer_set_tval(enum arch_timer timer, uint32_t tval)
+{
+	switch (timer) {
+	case VIRTUAL:
+		write_sysreg(tval, cntv_tval_el0);
+		break;
+	case PHYSICAL:
+		write_sysreg(tval, cntp_tval_el0);
+		break;
+	default:
+		GUEST_ASSERT_1(0, timer);
+	}
+
+	isb();
+}
+
+static inline void timer_set_ctl(enum arch_timer timer, uint32_t ctl)
+{
+	switch (timer) {
+	case VIRTUAL:
+		write_sysreg(ctl, cntv_ctl_el0);
+		break;
+	case PHYSICAL:
+		write_sysreg(ctl, cntp_ctl_el0);
+		break;
+	default:
+		GUEST_ASSERT_1(0, timer);
+	}
+
+	isb();
+}
+
+static inline uint32_t timer_get_ctl(enum arch_timer timer)
+{
+	switch (timer) {
+	case VIRTUAL:
+		return read_sysreg(cntv_ctl_el0);
+	case PHYSICAL:
+		return read_sysreg(cntp_ctl_el0);
+	default:
+		GUEST_ASSERT_1(0, timer);
+	}
+
+	/* We should not reach here */
+	return 0;
+}
+
+static inline void timer_set_next_cval_ms(enum arch_timer timer, uint32_t msec)
+{
+	uint64_t now_ct = timer_get_cntct(timer);
+	uint64_t next_ct = now_ct + msec_to_cycles(msec);
+
+	timer_set_cval(timer, next_ct);
+}
+
+static inline void timer_set_next_tval_ms(enum arch_timer timer, uint32_t msec)
+{
+	timer_set_tval(timer, msec_to_cycles(msec));
+}
+
+#endif /* SELFTEST_KVM_ARCH_TIMER_H */