paravirt.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/types.h>
#include <linux/interrupt.h>
#include <linux/irq_work.h>
#include <linux/jump_label.h>
#include <linux/kvm_para.h>
#include <linux/reboot.h>
#include <linux/static_call.h>
#include <asm/paravirt.h>

static int has_steal_clock;
struct static_key paravirt_steal_enabled;
struct static_key paravirt_steal_rq_enabled;
static DEFINE_PER_CPU(struct kvm_steal_time, steal_time) __aligned(64);
DEFINE_STATIC_KEY_FALSE(virt_spin_lock_key);

static u64 native_steal_clock(int cpu)
{
	return 0;
}

DEFINE_STATIC_CALL(pv_steal_clock, native_steal_clock);

static bool steal_acc = true;

static int __init parse_no_stealacc(char *arg)
{
	steal_acc = false;
	return 0;
}
early_param("no-steal-acc", parse_no_stealacc);

static u64 paravt_steal_clock(int cpu)
{
	int version;
	u64 steal;
	struct kvm_steal_time *src;

	src = &per_cpu(steal_time, cpu);
	do {

		version = src->version;
		virt_rmb(); /* Make sure that the version is read before the steal */
		steal = src->steal;
		virt_rmb(); /* Make sure that the steal is read before the next version */

	} while ((version & 1) || (version != src->version));

	return steal;
}

#ifdef CONFIG_SMP
static struct smp_ops native_ops;

static void pv_send_ipi_single(int cpu, unsigned int action)
{
	int min, old;
	irq_cpustat_t *info = &per_cpu(irq_stat, cpu);

	if (unlikely(action == ACTION_BOOT_CPU)) {
		native_ops.send_ipi_single(cpu, action);
		return;
	}

	old = atomic_fetch_or(BIT(action), &info->message);
	if (old)
		return;

	min = cpu_logical_map(cpu);
	kvm_hypercall3(KVM_HCALL_FUNC_IPI, 1, 0, min);
}

#define KVM_IPI_CLUSTER_SIZE	(2 * BITS_PER_LONG)

static void pv_send_ipi_mask(const struct cpumask *mask, unsigned int action)
{
	int i, cpu, min = 0, max = 0, old;
	__uint128_t bitmap = 0;
	irq_cpustat_t *info;

	if (cpumask_empty(mask))
		return;

	if (unlikely(action == ACTION_BOOT_CPU)) {
		native_ops.send_ipi_mask(mask, action);
		return;
	}

	action = BIT(action);
	for_each_cpu(i, mask) {
		info = &per_cpu(irq_stat, i);
		old = atomic_fetch_or(action, &info->message);
		if (old)
			continue;

		cpu = cpu_logical_map(i);
		if (!bitmap) {
			min = max = cpu;
		} else if (cpu < min && cpu > (max - KVM_IPI_CLUSTER_SIZE)) {
			/* cpu < min, and bitmap still enough */
			bitmap <<= min - cpu;
			min = cpu;
		} else if (cpu > min && cpu < (min + KVM_IPI_CLUSTER_SIZE)) {
			/* cpu > min, and bitmap still enough */
			max = cpu > max ? cpu : max;
		} else {
			/*
			 * With cpu, bitmap will exceed KVM_IPI_CLUSTER_SIZE,
			 * send IPI here directly and skip the remaining CPUs.
			 */
			kvm_hypercall3(KVM_HCALL_FUNC_IPI, (unsigned long)bitmap,
				      (unsigned long)(bitmap >> BITS_PER_LONG), min);
			min = max = cpu;
			bitmap = 0;
		}
		__set_bit(cpu - min, (unsigned long *)&bitmap);
	}

	if (bitmap)
		kvm_hypercall3(KVM_HCALL_FUNC_IPI, (unsigned long)bitmap,
			      (unsigned long)(bitmap >> BITS_PER_LONG), min);
}

static irqreturn_t pv_ipi_interrupt(int irq, void *dev)
{
	u32 action;
	irq_cpustat_t *info;

	/* Clear SWI interrupt */
	clear_csr_estat(1 << INT_SWI0);
	info = this_cpu_ptr(&irq_stat);
	action = atomic_xchg(&info->message, 0);

	if (action & SMP_RESCHEDULE) {
		scheduler_ipi();
		info->ipi_irqs[IPI_RESCHEDULE]++;
	}

	if (action & SMP_CALL_FUNCTION) {
		generic_smp_call_function_interrupt();
		info->ipi_irqs[IPI_CALL_FUNCTION]++;
	}

	if (action & SMP_IRQ_WORK) {
		irq_work_run();
		info->ipi_irqs[IPI_IRQ_WORK]++;
	}

	if (action & SMP_CLEAR_VECTOR) {
		complete_irq_moving();
		info->ipi_irqs[IPI_CLEAR_VECTOR]++;
	}

	return IRQ_HANDLED;
}

static void pv_init_ipi(void)
{
	int r, swi;

	/* Init native ipi irq for ACTION_BOOT_CPU */
	native_ops.init_ipi();
	swi = get_percpu_irq(INT_SWI0);
	if (swi < 0)
		panic("SWI0 IRQ mapping failed\n");
	irq_set_percpu_devid(swi);
	r = request_percpu_irq(swi, pv_ipi_interrupt, "SWI0-IPI", &irq_stat);
	if (r < 0)
		panic("SWI0 IRQ request failed\n");
}
#endif

bool kvm_para_available(void)
{
	int config;
	static int hypervisor_type;

	if (!cpu_has_hypervisor)
		return false;

	if (!hypervisor_type) {
		config = read_cpucfg(CPUCFG_KVM_SIG);
		if (!memcmp(&config, KVM_SIGNATURE, 4))
			hypervisor_type = HYPERVISOR_KVM;
	}

	return hypervisor_type == HYPERVISOR_KVM;
}

unsigned int kvm_arch_para_features(void)
{
	static unsigned int feature;

	if (!kvm_para_available())
		return 0;

	if (!feature)
		feature = read_cpucfg(CPUCFG_KVM_FEATURE);

	return feature;
}

int __init pv_ipi_init(void)
{
	if (!kvm_para_has_feature(KVM_FEATURE_IPI))
		return 0;

#ifdef CONFIG_SMP
	native_ops		= mp_ops;
	mp_ops.init_ipi		= pv_init_ipi;
	mp_ops.send_ipi_single	= pv_send_ipi_single;
	mp_ops.send_ipi_mask	= pv_send_ipi_mask;
#endif

	return 0;
}

static int pv_enable_steal_time(void)
{
	int cpu = smp_processor_id();
	unsigned long addr;
	struct kvm_steal_time *st;

	if (!has_steal_clock)
		return -EPERM;

	st = &per_cpu(steal_time, cpu);
	addr = per_cpu_ptr_to_phys(st);

	/* The whole structure kvm_steal_time should be in one page */
	if (PFN_DOWN(addr) != PFN_DOWN(addr + sizeof(*st))) {
		pr_warn("Illegal PV steal time addr %lx\n", addr);
		return -EFAULT;
	}

	addr |= KVM_STEAL_PHYS_VALID;
	kvm_hypercall2(KVM_HCALL_FUNC_NOTIFY, BIT(KVM_FEATURE_STEAL_TIME), addr);

	return 0;
}

static void pv_disable_steal_time(void)
{
	if (has_steal_clock)
		kvm_hypercall2(KVM_HCALL_FUNC_NOTIFY, BIT(KVM_FEATURE_STEAL_TIME), 0);
}

#ifdef CONFIG_SMP
static int pv_time_cpu_online(unsigned int cpu)
{
	unsigned long flags;

	local_irq_save(flags);
	pv_enable_steal_time();
	local_irq_restore(flags);

	return 0;
}

static int pv_time_cpu_down_prepare(unsigned int cpu)
{
	unsigned long flags;

	local_irq_save(flags);
	pv_disable_steal_time();
	local_irq_restore(flags);

	return 0;
}
#endif

static void pv_cpu_reboot(void *unused)
{
	pv_disable_steal_time();
}

static int pv_reboot_notify(struct notifier_block *nb, unsigned long code, void *unused)
{
	on_each_cpu(pv_cpu_reboot, NULL, 1);
	return NOTIFY_DONE;
}

static struct notifier_block pv_reboot_nb = {
	.notifier_call  = pv_reboot_notify,
};

int __init pv_time_init(void)
{
	int r;

	if (!kvm_para_has_feature(KVM_FEATURE_STEAL_TIME))
		return 0;

	has_steal_clock = 1;
	r = pv_enable_steal_time();
	if (r < 0) {
		has_steal_clock = 0;
		return 0;
	}
	register_reboot_notifier(&pv_reboot_nb);

#ifdef CONFIG_SMP
	r = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
				      "loongarch/pv_time:online",
				      pv_time_cpu_online, pv_time_cpu_down_prepare);
	if (r < 0) {
		has_steal_clock = 0;
		pr_err("Failed to install cpu hotplug callbacks\n");
		return r;
	}
#endif

	static_call_update(pv_steal_clock, paravt_steal_clock);

	static_key_slow_inc(&paravirt_steal_enabled);
#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
	if (steal_acc)
		static_key_slow_inc(&paravirt_steal_rq_enabled);
#endif

	pr_info("Using paravirt steal-time\n");

	return 0;
}

int __init pv_spinlock_init(void)
{
	if (!cpu_has_hypervisor)
		return 0;

	static_branch_enable(&virt_spin_lock_key);

	return 0;
}