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/*
* 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.
*/
#include "hf/arch/timer.h"
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include "hf/arch/cpu.h"
#include "hf/addr.h"
#include "msr.h"
#define CNTV_CTL_EL0_ENABLE (1u << 0)
#define CNTV_CTL_EL0_IMASK (1u << 1)
#define CNTV_CTL_EL0_ISTATUS (1u << 2)
#define NANOS_PER_UNIT 1000000000
/**
* Sets the bit to mask virtual timer interrupts.
*/
void arch_timer_mask(struct arch_regs *regs)
{
regs->lazy.cntv_ctl_el0 |= CNTV_CTL_EL0_IMASK;
}
/**
* Checks whether the virtual timer is enabled and its interrupt not masked.
*/
bool arch_timer_enabled(struct arch_regs *regs)
{
uintreg_t cntv_ctl_el0 = regs->lazy.cntv_ctl_el0;
return (cntv_ctl_el0 & CNTV_CTL_EL0_ENABLE) &&
!(cntv_ctl_el0 & CNTV_CTL_EL0_IMASK);
}
/**
* Converts a number of timer ticks to the equivalent number of nanoseconds.
*/
static uint64_t ticks_to_ns(uint64_t ticks)
{
return (ticks * NANOS_PER_UNIT) / read_msr(cntfrq_el0);
}
/**
* 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)
{
/*
* Calculate the value from the saved CompareValue (cntv_cval_el0) and
* the virtual count value.
*/
uintreg_t cntv_cval_el0 = regs->lazy.cntv_cval_el0;
uintreg_t cntvct_el0 = read_msr(cntvct_el0);
if (cntv_cval_el0 >= cntvct_el0) {
return cntv_cval_el0 - cntvct_el0;
}
return 0;
}
/**
* 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)
{
return ticks_to_ns(arch_timer_remaining_ticks(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)
{
if (!arch_timer_enabled(regs)) {
return false;
}
if (regs->lazy.cntv_ctl_el0 & CNTV_CTL_EL0_ISTATUS) {
return true;
}
if (arch_timer_remaining_ticks(regs) == 0) {
/*
* This can happen even if the (stored) ISTATUS bit is not set,
* because time has passed between when the registers were
* stored and now.
*/
return true;
}
return false;
}
/**
* Checks whether the virtual timer is enabled and its interrupt not masked, for
* the currently active vCPU.
*/
bool arch_timer_enabled_current(void)
{
uintreg_t cntv_ctl_el0 = read_msr(cntv_ctl_el0);
return (cntv_ctl_el0 & CNTV_CTL_EL0_ENABLE) &&
!(cntv_ctl_el0 & CNTV_CTL_EL0_IMASK);
}
/**
* 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)
{
uintreg_t cntv_cval_el0 = read_msr(cntv_cval_el0);
uintreg_t cntvct_el0 = read_msr(cntvct_el0);
if (cntv_cval_el0 >= cntvct_el0) {
return cntv_cval_el0 - cntvct_el0;
}
return 0;
}
/**
* 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)
{
return ticks_to_ns(arch_timer_remaining_ticks_current());
}