arch/riscv/kvm/vcpu_timer.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2019 Western Digital Corporation or its affiliates.
  *
  * Authors:
  *     Atish Patra <atish.patra@wdc.com>
  */

 #include <linux/errno.h>
 #include <linux/err.h>
 #include <linux/kvm_host.h>
 #include <linux/uaccess.h>
 #include <clocksource/timer-riscv.h>
 #include <asm/csr.h>
 #include <asm/delay.h>
 #include <asm/kvm_vcpu_timer.h>

 static u64 kvm_riscv_current_cycles(struct kvm_guest_timer *gt)
 {
 	return get_cycles64() + gt->time_delta;
 }

 static u64 kvm_riscv_delta_cycles2ns(u64 cycles,
 				     struct kvm_guest_timer *gt,
 				     struct kvm_vcpu_timer *t)
 {
 	unsigned long flags;
 	u64 cycles_now, cycles_delta, delta_ns;

 	local_irq_save(flags);
 	cycles_now = kvm_riscv_current_cycles(gt);
 	if (cycles_now < cycles)
 		cycles_delta = cycles - cycles_now;
 	else
 		cycles_delta = 0;
 	delta_ns = (cycles_delta * gt->nsec_mult) >> gt->nsec_shift;
 	local_irq_restore(flags);

 	return delta_ns;
 }

 static enum hrtimer_restart kvm_riscv_vcpu_hrtimer_expired(struct hrtimer *h)
 {
 	u64 delta_ns;
 	struct kvm_vcpu_timer *t = container_of(h, struct kvm_vcpu_timer, hrt);
 	struct kvm_vcpu *vcpu = container_of(t, struct kvm_vcpu, arch.timer);
 	struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;

 	if (kvm_riscv_current_cycles(gt) < t->next_cycles) {
 		delta_ns = kvm_riscv_delta_cycles2ns(t->next_cycles, gt, t);
 		hrtimer_forward_now(&t->hrt, ktime_set(0, delta_ns));
 		return HRTIMER_RESTART;
 	}

 	t->next_set = false;
 	kvm_riscv_vcpu_set_interrupt(vcpu, IRQ_VS_TIMER);

 	return HRTIMER_NORESTART;
 }

 static int kvm_riscv_vcpu_timer_cancel(struct kvm_vcpu_timer *t)
 {
 	if (!t->init_done || !t->next_set)
 		return -EINVAL;

 	hrtimer_cancel(&t->hrt);
 	t->next_set = false;

 	return 0;
 }

 static int kvm_riscv_vcpu_update_vstimecmp(struct kvm_vcpu *vcpu, u64 ncycles)
 {
 #if defined(CONFIG_32BIT)
 		csr_write(CSR_VSTIMECMP, ncycles & 0xFFFFFFFF);
 		csr_write(CSR_VSTIMECMPH, ncycles >> 32);
 #else
 		csr_write(CSR_VSTIMECMP, ncycles);
 #endif
 		return 0;
 }

 static int kvm_riscv_vcpu_update_hrtimer(struct kvm_vcpu *vcpu, u64 ncycles)
 {
 	struct kvm_vcpu_timer *t = &vcpu->arch.timer;
 	struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;
 	u64 delta_ns;

 	if (!t->init_done)
 		return -EINVAL;

 	kvm_riscv_vcpu_unset_interrupt(vcpu, IRQ_VS_TIMER);

 	delta_ns = kvm_riscv_delta_cycles2ns(ncycles, gt, t);
 	t->next_cycles = ncycles;
 	hrtimer_start(&t->hrt, ktime_set(0, delta_ns), HRTIMER_MODE_REL);
 	t->next_set = true;

 	return 0;
 }

 int kvm_riscv_vcpu_timer_next_event(struct kvm_vcpu *vcpu, u64 ncycles)
 {
 	struct kvm_vcpu_timer *t = &vcpu->arch.timer;

 	return t->timer_next_event(vcpu, ncycles);
 }

 static enum hrtimer_restart kvm_riscv_vcpu_vstimer_expired(struct hrtimer *h)
 {
 	u64 delta_ns;
 	struct kvm_vcpu_timer *t = container_of(h, struct kvm_vcpu_timer, hrt);
 	struct kvm_vcpu *vcpu = container_of(t, struct kvm_vcpu, arch.timer);
 	struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;

 	if (kvm_riscv_current_cycles(gt) < t->next_cycles) {
 		delta_ns = kvm_riscv_delta_cycles2ns(t->next_cycles, gt, t);
 		hrtimer_forward_now(&t->hrt, ktime_set(0, delta_ns));
 		return HRTIMER_RESTART;
 	}

 	t->next_set = false;
 	kvm_vcpu_kick(vcpu);

 	return HRTIMER_NORESTART;
 }

 bool kvm_riscv_vcpu_timer_pending(struct kvm_vcpu *vcpu)
 {
 	struct kvm_vcpu_timer *t = &vcpu->arch.timer;
 	struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;

 	if (!kvm_riscv_delta_cycles2ns(t->next_cycles, gt, t) ||
 	    kvm_riscv_vcpu_has_interrupts(vcpu, 1UL << IRQ_VS_TIMER))
 		return true;
 	else
 		return false;
 }

 static void kvm_riscv_vcpu_timer_blocking(struct kvm_vcpu *vcpu)
 {
 	struct kvm_vcpu_timer *t = &vcpu->arch.timer;
 	struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;
 	u64 delta_ns;

 	if (!t->init_done)
 		return;

 	delta_ns = kvm_riscv_delta_cycles2ns(t->next_cycles, gt, t);
 	if (delta_ns) {
 		hrtimer_start(&t->hrt, ktime_set(0, delta_ns), HRTIMER_MODE_REL);
 		t->next_set = true;
 	}
 }

 static void kvm_riscv_vcpu_timer_unblocking(struct kvm_vcpu *vcpu)
 {
 	kvm_riscv_vcpu_timer_cancel(&vcpu->arch.timer);
 }

 int kvm_riscv_vcpu_get_reg_timer(struct kvm_vcpu *vcpu,
 				 const struct kvm_one_reg *reg)
 {
 	struct kvm_vcpu_timer *t = &vcpu->arch.timer;
 	struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;
 	u64 __user *uaddr = (u64 __user *)(unsigned long)reg->addr;
 	unsigned long reg_num = reg->id & ~(KVM_REG_ARCH_MASK |
 					    KVM_REG_SIZE_MASK |
 					    KVM_REG_RISCV_TIMER);
 	u64 reg_val;

 	if (KVM_REG_SIZE(reg->id) != sizeof(u64))
 		return -EINVAL;
 	if (reg_num >= sizeof(struct kvm_riscv_timer) / sizeof(u64))
 		return -EINVAL;

 	switch (reg_num) {
 	case KVM_REG_RISCV_TIMER_REG(frequency):
 		reg_val = riscv_timebase;
 		break;
 	case KVM_REG_RISCV_TIMER_REG(time):
 		reg_val = kvm_riscv_current_cycles(gt);
 		break;
 	case KVM_REG_RISCV_TIMER_REG(compare):
 		reg_val = t->next_cycles;
 		break;
 	case KVM_REG_RISCV_TIMER_REG(state):
 		reg_val = (t->next_set) ? KVM_RISCV_TIMER_STATE_ON :
 					  KVM_RISCV_TIMER_STATE_OFF;
 		break;
 	default:
 		return -EINVAL;
 	}

 	if (copy_to_user(uaddr, &reg_val, KVM_REG_SIZE(reg->id)))
 		return -EFAULT;

 	return 0;
 }

 int kvm_riscv_vcpu_set_reg_timer(struct kvm_vcpu *vcpu,
 				 const struct kvm_one_reg *reg)
 {
 	struct kvm_vcpu_timer *t = &vcpu->arch.timer;
 	struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;
 	u64 __user *uaddr = (u64 __user *)(unsigned long)reg->addr;
 	unsigned long reg_num = reg->id & ~(KVM_REG_ARCH_MASK |
 					    KVM_REG_SIZE_MASK |
 					    KVM_REG_RISCV_TIMER);
 	u64 reg_val;
 	int ret = 0;

 	if (KVM_REG_SIZE(reg->id) != sizeof(u64))
 		return -EINVAL;
 	if (reg_num >= sizeof(struct kvm_riscv_timer) / sizeof(u64))
 		return -EINVAL;

 	if (copy_from_user(&reg_val, uaddr, KVM_REG_SIZE(reg->id)))
 		return -EFAULT;

 	switch (reg_num) {
 	case KVM_REG_RISCV_TIMER_REG(frequency):
 		ret = -EOPNOTSUPP;
 		break;
 	case KVM_REG_RISCV_TIMER_REG(time):
 		gt->time_delta = reg_val - get_cycles64();
 		break;
 	case KVM_REG_RISCV_TIMER_REG(compare):
 		t->next_cycles = reg_val;
 		break;
 	case KVM_REG_RISCV_TIMER_REG(state):
 		if (reg_val == KVM_RISCV_TIMER_STATE_ON)
 			ret = kvm_riscv_vcpu_timer_next_event(vcpu, reg_val);
 		else
 			ret = kvm_riscv_vcpu_timer_cancel(t);
 		break;
 	default:
 		ret = -EINVAL;
 		break;
 	}

 	return ret;
 }

 int kvm_riscv_vcpu_timer_init(struct kvm_vcpu *vcpu)
 {
 	struct kvm_vcpu_timer *t = &vcpu->arch.timer;

 	if (t->init_done)
 		return -EINVAL;

 	hrtimer_init(&t->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	t->init_done = true;
 	t->next_set = false;

 	/* Enable sstc for every vcpu if available in hardware */
 	if (riscv_isa_extension_available(NULL, SSTC)) {
 		t->sstc_enabled = true;
 		t->hrt.function = kvm_riscv_vcpu_vstimer_expired;
 		t->timer_next_event = kvm_riscv_vcpu_update_vstimecmp;
 	} else {
 		t->sstc_enabled = false;
 		t->hrt.function = kvm_riscv_vcpu_hrtimer_expired;
 		t->timer_next_event = kvm_riscv_vcpu_update_hrtimer;
 	}

 	return 0;
 }

 int kvm_riscv_vcpu_timer_deinit(struct kvm_vcpu *vcpu)
 {
 	int ret;

 	ret = kvm_riscv_vcpu_timer_cancel(&vcpu->arch.timer);
 	vcpu->arch.timer.init_done = false;

 	return ret;
 }

 int kvm_riscv_vcpu_timer_reset(struct kvm_vcpu *vcpu)
 {
 	struct kvm_vcpu_timer *t = &vcpu->arch.timer;

 	t->next_cycles = -1ULL;
 	return kvm_riscv_vcpu_timer_cancel(&vcpu->arch.timer);
 }

 static void kvm_riscv_vcpu_update_timedelta(struct kvm_vcpu *vcpu)
 {
 	struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;

 #if defined(CONFIG_32BIT)
 	csr_write(CSR_HTIMEDELTA, (u32)(gt->time_delta));
 	csr_write(CSR_HTIMEDELTAH, (u32)(gt->time_delta >> 32));
 #else
 	csr_write(CSR_HTIMEDELTA, gt->time_delta);
 #endif
 }

 void kvm_riscv_vcpu_timer_restore(struct kvm_vcpu *vcpu)
 {
 	struct kvm_vcpu_timer *t = &vcpu->arch.timer;

 	kvm_riscv_vcpu_update_timedelta(vcpu);

 	if (!t->sstc_enabled)
 		return;

 #if defined(CONFIG_32BIT)
 	csr_write(CSR_VSTIMECMP, (u32)t->next_cycles);
 	csr_write(CSR_VSTIMECMPH, (u32)(t->next_cycles >> 32));
 #else
 	csr_write(CSR_VSTIMECMP, t->next_cycles);
 #endif

 	/* timer should be enabled for the remaining operations */
 	if (unlikely(!t->init_done))
 		return;

 	kvm_riscv_vcpu_timer_unblocking(vcpu);
 }

 void kvm_riscv_vcpu_timer_sync(struct kvm_vcpu *vcpu)
 {
 	struct kvm_vcpu_timer *t = &vcpu->arch.timer;

 	if (!t->sstc_enabled)
 		return;

 #if defined(CONFIG_32BIT)
 	t->next_cycles = csr_read(CSR_VSTIMECMP);
 	t->next_cycles |= (u64)csr_read(CSR_VSTIMECMPH) << 32;
 #else
 	t->next_cycles = csr_read(CSR_VSTIMECMP);
 #endif
 }

 void kvm_riscv_vcpu_timer_save(struct kvm_vcpu *vcpu)
 {
 	struct kvm_vcpu_timer *t = &vcpu->arch.timer;

 	if (!t->sstc_enabled)
 		return;

 	/*
 	 * The vstimecmp CSRs are saved by kvm_riscv_vcpu_timer_sync()
 	 * upon every VM exit so no need to save here.
 	 */

 	/* timer should be enabled for the remaining operations */
 	if (unlikely(!t->init_done))
 		return;

 	if (kvm_vcpu_is_blocking(vcpu))
 		kvm_riscv_vcpu_timer_blocking(vcpu);
 }

 void kvm_riscv_guest_timer_init(struct kvm *kvm)
 {
 	struct kvm_guest_timer *gt = &kvm->arch.timer;

 	riscv_cs_get_mult_shift(&gt->nsec_mult, &gt->nsec_shift);
 	gt->time_delta = -get_cycles64();
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Copyright (C) 2019 Western Digital Corporation or its affiliates.
	*
	* Authors:
	* Atish Patra <atish.patra@wdc.com>
	*/

	#include <linux/errno.h>
	#include <linux/err.h>
	#include <linux/kvm_host.h>
	#include <linux/uaccess.h>
	#include <clocksource/timer-riscv.h>
	#include <asm/csr.h>
	#include <asm/delay.h>
	#include <asm/kvm_vcpu_timer.h>

	static u64 kvm_riscv_current_cycles(struct kvm_guest_timer *gt)
	{
	return get_cycles64() + gt->time_delta;
	}

	static u64 kvm_riscv_delta_cycles2ns(u64 cycles,
	struct kvm_guest_timer *gt,
	struct kvm_vcpu_timer *t)
	{
	unsigned long flags;
	u64 cycles_now, cycles_delta, delta_ns;

	local_irq_save(flags);
	cycles_now = kvm_riscv_current_cycles(gt);
	if (cycles_now < cycles)
	cycles_delta = cycles - cycles_now;
	else
	cycles_delta = 0;
	delta_ns = (cycles_delta * gt->nsec_mult) >> gt->nsec_shift;
	local_irq_restore(flags);

	return delta_ns;
	}

	static enum hrtimer_restart kvm_riscv_vcpu_hrtimer_expired(struct hrtimer *h)
	{
	u64 delta_ns;
	struct kvm_vcpu_timer *t = container_of(h, struct kvm_vcpu_timer, hrt);
	struct kvm_vcpu *vcpu = container_of(t, struct kvm_vcpu, arch.timer);
	struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;

	if (kvm_riscv_current_cycles(gt) < t->next_cycles) {
	delta_ns = kvm_riscv_delta_cycles2ns(t->next_cycles, gt, t);
	hrtimer_forward_now(&t->hrt, ktime_set(0, delta_ns));
	return HRTIMER_RESTART;
	}

	t->next_set = false;
	kvm_riscv_vcpu_set_interrupt(vcpu, IRQ_VS_TIMER);

	return HRTIMER_NORESTART;
	}

	static int kvm_riscv_vcpu_timer_cancel(struct kvm_vcpu_timer *t)
	{
	if (!t->init_done \|\| !t->next_set)
	return -EINVAL;

	hrtimer_cancel(&t->hrt);
	t->next_set = false;

	return 0;
	}

	static int kvm_riscv_vcpu_update_vstimecmp(struct kvm_vcpu *vcpu, u64 ncycles)
	{
	#if defined(CONFIG_32BIT)
	csr_write(CSR_VSTIMECMP, ncycles & 0xFFFFFFFF);
	csr_write(CSR_VSTIMECMPH, ncycles >> 32);
	#else
	csr_write(CSR_VSTIMECMP, ncycles);
	#endif
	return 0;
	}

	static int kvm_riscv_vcpu_update_hrtimer(struct kvm_vcpu *vcpu, u64 ncycles)
	{
	struct kvm_vcpu_timer *t = &vcpu->arch.timer;
	struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;
	u64 delta_ns;

	if (!t->init_done)
	return -EINVAL;

	kvm_riscv_vcpu_unset_interrupt(vcpu, IRQ_VS_TIMER);

	delta_ns = kvm_riscv_delta_cycles2ns(ncycles, gt, t);
	t->next_cycles = ncycles;
	hrtimer_start(&t->hrt, ktime_set(0, delta_ns), HRTIMER_MODE_REL);
	t->next_set = true;

	return 0;
	}

	int kvm_riscv_vcpu_timer_next_event(struct kvm_vcpu *vcpu, u64 ncycles)
	{
	struct kvm_vcpu_timer *t = &vcpu->arch.timer;

	return t->timer_next_event(vcpu, ncycles);
	}

	static enum hrtimer_restart kvm_riscv_vcpu_vstimer_expired(struct hrtimer *h)
	{
	u64 delta_ns;
	struct kvm_vcpu_timer *t = container_of(h, struct kvm_vcpu_timer, hrt);
	struct kvm_vcpu *vcpu = container_of(t, struct kvm_vcpu, arch.timer);
	struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;

	if (kvm_riscv_current_cycles(gt) < t->next_cycles) {
	delta_ns = kvm_riscv_delta_cycles2ns(t->next_cycles, gt, t);
	hrtimer_forward_now(&t->hrt, ktime_set(0, delta_ns));
	return HRTIMER_RESTART;
	}

	t->next_set = false;
	kvm_vcpu_kick(vcpu);

	return HRTIMER_NORESTART;
	}

	bool kvm_riscv_vcpu_timer_pending(struct kvm_vcpu *vcpu)
	{
	struct kvm_vcpu_timer *t = &vcpu->arch.timer;
	struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;

	if (!kvm_riscv_delta_cycles2ns(t->next_cycles, gt, t) \|\|
	kvm_riscv_vcpu_has_interrupts(vcpu, 1UL << IRQ_VS_TIMER))
	return true;
	else
	return false;
	}

	static void kvm_riscv_vcpu_timer_blocking(struct kvm_vcpu *vcpu)
	{
	struct kvm_vcpu_timer *t = &vcpu->arch.timer;
	struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;
	u64 delta_ns;

	if (!t->init_done)
	return;

	delta_ns = kvm_riscv_delta_cycles2ns(t->next_cycles, gt, t);
	if (delta_ns) {
	hrtimer_start(&t->hrt, ktime_set(0, delta_ns), HRTIMER_MODE_REL);
	t->next_set = true;
	}
	}

	static void kvm_riscv_vcpu_timer_unblocking(struct kvm_vcpu *vcpu)
	{
	kvm_riscv_vcpu_timer_cancel(&vcpu->arch.timer);
	}

	int kvm_riscv_vcpu_get_reg_timer(struct kvm_vcpu *vcpu,
	const struct kvm_one_reg *reg)
	{
	struct kvm_vcpu_timer *t = &vcpu->arch.timer;
	struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;
	u64 __user uaddr = (u64 __user )(unsigned long)reg->addr;
	unsigned long reg_num = reg->id & ~(KVM_REG_ARCH_MASK \|
	KVM_REG_SIZE_MASK \|
	KVM_REG_RISCV_TIMER);
	u64 reg_val;

	if (KVM_REG_SIZE(reg->id) != sizeof(u64))
	return -EINVAL;
	if (reg_num >= sizeof(struct kvm_riscv_timer) / sizeof(u64))
	return -EINVAL;

	switch (reg_num) {
	case KVM_REG_RISCV_TIMER_REG(frequency):
	reg_val = riscv_timebase;
	break;
	case KVM_REG_RISCV_TIMER_REG(time):
	reg_val = kvm_riscv_current_cycles(gt);
	break;
	case KVM_REG_RISCV_TIMER_REG(compare):
	reg_val = t->next_cycles;
	break;
	case KVM_REG_RISCV_TIMER_REG(state):
	reg_val = (t->next_set) ? KVM_RISCV_TIMER_STATE_ON :
	KVM_RISCV_TIMER_STATE_OFF;
	break;
	default:
	return -EINVAL;
	}

	if (copy_to_user(uaddr, &reg_val, KVM_REG_SIZE(reg->id)))
	return -EFAULT;

	return 0;
	}

	int kvm_riscv_vcpu_set_reg_timer(struct kvm_vcpu *vcpu,
	const struct kvm_one_reg *reg)
	{
	struct kvm_vcpu_timer *t = &vcpu->arch.timer;
	struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;
	u64 __user uaddr = (u64 __user )(unsigned long)reg->addr;
	unsigned long reg_num = reg->id & ~(KVM_REG_ARCH_MASK \|
	KVM_REG_SIZE_MASK \|
	KVM_REG_RISCV_TIMER);
	u64 reg_val;
	int ret = 0;

	if (KVM_REG_SIZE(reg->id) != sizeof(u64))
	return -EINVAL;
	if (reg_num >= sizeof(struct kvm_riscv_timer) / sizeof(u64))
	return -EINVAL;

	if (copy_from_user(&reg_val, uaddr, KVM_REG_SIZE(reg->id)))
	return -EFAULT;

	switch (reg_num) {
	case KVM_REG_RISCV_TIMER_REG(frequency):
	ret = -EOPNOTSUPP;
	break;
	case KVM_REG_RISCV_TIMER_REG(time):
	gt->time_delta = reg_val - get_cycles64();
	break;
	case KVM_REG_RISCV_TIMER_REG(compare):
	t->next_cycles = reg_val;
	break;
	case KVM_REG_RISCV_TIMER_REG(state):
	if (reg_val == KVM_RISCV_TIMER_STATE_ON)
	ret = kvm_riscv_vcpu_timer_next_event(vcpu, reg_val);
	else
	ret = kvm_riscv_vcpu_timer_cancel(t);
	break;
	default:
	ret = -EINVAL;
	break;
	}

	return ret;
	}

	int kvm_riscv_vcpu_timer_init(struct kvm_vcpu *vcpu)
	{
	struct kvm_vcpu_timer *t = &vcpu->arch.timer;

	if (t->init_done)
	return -EINVAL;

	hrtimer_init(&t->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	t->init_done = true;
	t->next_set = false;

	/* Enable sstc for every vcpu if available in hardware */
	if (riscv_isa_extension_available(NULL, SSTC)) {
	t->sstc_enabled = true;
	t->hrt.function = kvm_riscv_vcpu_vstimer_expired;
	t->timer_next_event = kvm_riscv_vcpu_update_vstimecmp;
	} else {
	t->sstc_enabled = false;
	t->hrt.function = kvm_riscv_vcpu_hrtimer_expired;
	t->timer_next_event = kvm_riscv_vcpu_update_hrtimer;
	}

	return 0;
	}

	int kvm_riscv_vcpu_timer_deinit(struct kvm_vcpu *vcpu)
	{
	int ret;

	ret = kvm_riscv_vcpu_timer_cancel(&vcpu->arch.timer);
	vcpu->arch.timer.init_done = false;

	return ret;
	}

	int kvm_riscv_vcpu_timer_reset(struct kvm_vcpu *vcpu)
	{
	struct kvm_vcpu_timer *t = &vcpu->arch.timer;

	t->next_cycles = -1ULL;
	return kvm_riscv_vcpu_timer_cancel(&vcpu->arch.timer);
	}

	static void kvm_riscv_vcpu_update_timedelta(struct kvm_vcpu *vcpu)
	{
	struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;

	#if defined(CONFIG_32BIT)
	csr_write(CSR_HTIMEDELTA, (u32)(gt->time_delta));
	csr_write(CSR_HTIMEDELTAH, (u32)(gt->time_delta >> 32));
	#else
	csr_write(CSR_HTIMEDELTA, gt->time_delta);
	#endif
	}

	void kvm_riscv_vcpu_timer_restore(struct kvm_vcpu *vcpu)
	{
	struct kvm_vcpu_timer *t = &vcpu->arch.timer;

	kvm_riscv_vcpu_update_timedelta(vcpu);

	if (!t->sstc_enabled)
	return;

	#if defined(CONFIG_32BIT)
	csr_write(CSR_VSTIMECMP, (u32)t->next_cycles);
	csr_write(CSR_VSTIMECMPH, (u32)(t->next_cycles >> 32));
	#else
	csr_write(CSR_VSTIMECMP, t->next_cycles);
	#endif

	/* timer should be enabled for the remaining operations */
	if (unlikely(!t->init_done))
	return;

	kvm_riscv_vcpu_timer_unblocking(vcpu);
	}

	void kvm_riscv_vcpu_timer_sync(struct kvm_vcpu *vcpu)
	{
	struct kvm_vcpu_timer *t = &vcpu->arch.timer;

	if (!t->sstc_enabled)
	return;

	#if defined(CONFIG_32BIT)
	t->next_cycles = csr_read(CSR_VSTIMECMP);
	t->next_cycles \|= (u64)csr_read(CSR_VSTIMECMPH) << 32;
	#else
	t->next_cycles = csr_read(CSR_VSTIMECMP);
	#endif
	}

	void kvm_riscv_vcpu_timer_save(struct kvm_vcpu *vcpu)
	{
	struct kvm_vcpu_timer *t = &vcpu->arch.timer;

	if (!t->sstc_enabled)
	return;

	/*
	* The vstimecmp CSRs are saved by kvm_riscv_vcpu_timer_sync()
	* upon every VM exit so no need to save here.
	*/

	/* timer should be enabled for the remaining operations */
	if (unlikely(!t->init_done))
	return;

	if (kvm_vcpu_is_blocking(vcpu))
	kvm_riscv_vcpu_timer_blocking(vcpu);
	}

	void kvm_riscv_guest_timer_init(struct kvm *kvm)
	{
	struct kvm_guest_timer *gt = &kvm->arch.timer;

	riscv_cs_get_mult_shift(&gt->nsec_mult, &gt->nsec_shift);
	gt->time_delta = -get_cycles64();
	}