// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2019 Western Digital Corporation or its affiliates.
 *
 * Authors:
 *     Anup Patel <anup.patel@wdc.com>
 */

#include <linux/errno.h>
#include <linux/err.h>
#include <linux/module.h>
#include <linux/kvm_host.h>
#include <linux/cpu_pm.h>
#include <asm/cpufeature.h>
#include <asm/kvm_mmu.h>
#include <asm/kvm_nacl.h>
#include <asm/sbi.h>
#include <asm/kvm_vcpu_vector.h>

static DEFINE_PER_CPU(bool, kvm_riscv_virtualization_enabled);

DEFINE_STATIC_KEY_FALSE(kvm_riscv_vsstage_tlb_no_gpa);

static void kvm_riscv_setup_vendor_features(void)
{
	/* Andes AX66: split two-stage TLBs */
	if (riscv_cached_mvendorid(0) == ANDES_VENDOR_ID &&
	    (riscv_cached_marchid(0) & 0xFFFF) == 0x8A66) {
		static_branch_enable(&kvm_riscv_vsstage_tlb_no_gpa);
		kvm_info("VS-stage TLB does not cache guest physical address and VMID\n");
	}
}

long kvm_arch_dev_ioctl(struct file *filp,
			unsigned int ioctl, unsigned long arg)
{
	return -EINVAL;
}

/* Initialize hypervisor CSRs - called during CPU online and non-retention idle resume */
static void kvm_riscv_csr_init(void)
{
	csr_write(CSR_HEDELEG, 0);
	csr_write(CSR_HIDELEG, 0);

	/* VS should access only the time counter directly. Everything else should trap */
	csr_write(CSR_HCOUNTEREN, 0x02);

	csr_write(CSR_HVIP, 0);
}

/* Clear hypervisor CSRs - called during CPU offline and non-retention idle entry */
static void kvm_riscv_csr_cleanup(void)
{
	/*
	 * After clearing the hideleg CSR, the host kernel will receive
	 * spurious interrupts if hvip CSR has pending interrupts and the
	 * corresponding enable bits in vsie CSR are asserted. To avoid it,
	 * hvip CSR and vsie CSR must be cleared before clearing hideleg CSR.
	 */
	csr_write(CSR_VSIE, 0);
	csr_write(CSR_HVIP, 0);
	csr_write(CSR_HEDELEG, 0);
	csr_write(CSR_HIDELEG, 0);

	kvm_riscv_clear_former_vcpu();
}

int kvm_arch_enable_virtualization_cpu(void)
{
	int rc;

	rc = kvm_riscv_nacl_enable();
	if (rc)
		return rc;

	kvm_riscv_csr_init();
	kvm_riscv_aia_enable();

	__this_cpu_write(kvm_riscv_virtualization_enabled, true);

	return 0;
}

void kvm_arch_disable_virtualization_cpu(void)
{
	kvm_riscv_aia_disable();
	kvm_riscv_csr_cleanup();
	kvm_riscv_nacl_disable();

	__this_cpu_write(kvm_riscv_virtualization_enabled, false);
}

static int kvm_riscv_cpu_pm_notifier(struct notifier_block *self, unsigned long cmd, void *v)
{
	switch (cmd) {
	case CPU_PM_EXIT:
	case CPU_PM_ENTER_FAILED:
		/*
		 * Only restore hypervisor state if KVM virtualization is
		 * enabled on this CPU. This prevents unintentional re-enabling
		 * of virtualization after it has been explicitly disabled.
		 */
		if (__this_cpu_read(kvm_riscv_virtualization_enabled)) {
			kvm_riscv_csr_init();
			kvm_riscv_aia_pm_exit();
		}
		return NOTIFY_OK;
	case CPU_PM_ENTER:
		/*
		 * Only save and clear hypervisor state if KVM virtualization
		 * is enabled on this CPU.
		 */
		if (__this_cpu_read(kvm_riscv_virtualization_enabled)) {
			kvm_riscv_aia_pm_enter();
			kvm_riscv_csr_cleanup();
		}
		return NOTIFY_OK;
	default:
		break;
	}

	return NOTIFY_DONE;
}

static struct notifier_block kvm_riscv_cpu_pm_nb = {
	.notifier_call = kvm_riscv_cpu_pm_notifier,
};

static void kvm_riscv_teardown(void)
{
	kvm_riscv_aia_exit();
	kvm_riscv_nacl_exit();
	kvm_riscv_v_exit();
	kvm_unregister_perf_callbacks();
}

static int __init riscv_kvm_init(void)
{
	int rc;
	char slist[64];
	const char *str;

	if (!riscv_isa_extension_available(NULL, H)) {
		kvm_info("hypervisor extension not available\n");
		return -ENODEV;
	}

	if (sbi_spec_is_0_1()) {
		kvm_info("require SBI v0.2 or higher\n");
		return -ENODEV;
	}

	if (!sbi_probe_extension(SBI_EXT_RFENCE)) {
		kvm_info("require SBI RFENCE extension\n");
		return -ENODEV;
	}

	rc = kvm_riscv_nacl_init();
	if (rc && rc != -ENODEV)
		return rc;

	kvm_riscv_gstage_mode_detect();
	switch (kvm_riscv_gstage_max_pgd_levels) {
	case 2:
		str = "Sv32x4";
		break;
	case 3:
		str = "Sv39x4";
		break;
	case 4:
		str = "Sv48x4";
		break;
	case 5:
		str = "Sv57x4";
		break;
	default:
		kvm_riscv_nacl_exit();
		return -ENODEV;
	}

	kvm_riscv_gstage_vmid_detect();

	rc = kvm_riscv_aia_init();
	if (rc && rc != -ENODEV) {
		kvm_riscv_nacl_exit();
		return rc;
	}

	kvm_info("hypervisor extension available\n");

	if (kvm_riscv_nacl_available()) {
		rc = 0;
		slist[0] = '\0';
		if (kvm_riscv_nacl_sync_csr_available()) {
			if (rc)
				strcat(slist, ", ");
			strcat(slist, "sync_csr");
			rc++;
		}
		if (kvm_riscv_nacl_sync_hfence_available()) {
			if (rc)
				strcat(slist, ", ");
			strcat(slist, "sync_hfence");
			rc++;
		}
		if (kvm_riscv_nacl_sync_sret_available()) {
			if (rc)
				strcat(slist, ", ");
			strcat(slist, "sync_sret");
			rc++;
		}
		if (kvm_riscv_nacl_autoswap_csr_available()) {
			if (rc)
				strcat(slist, ", ");
			strcat(slist, "autoswap_csr");
			rc++;
		}
		kvm_info("using SBI nested acceleration with %s\n",
			 (rc) ? slist : "no features");
	}

	kvm_info("highest G-stage page table mode is %s\n", str);

	kvm_info("VMID %ld bits available\n", kvm_riscv_gstage_vmid_bits());

	kvm_riscv_setup_vendor_features();

	kvm_riscv_v_init();

	kvm_register_perf_callbacks();

	/* Register CPU PM notifier for CPU idle non-retention states */
	if (IS_ENABLED(CONFIG_CPU_PM)) {
		rc = cpu_pm_register_notifier(&kvm_riscv_cpu_pm_nb);
		if (rc) {
			kvm_err("Failed to register CPU PM notifier: %d\n", rc);
			goto err_teardown;
		}
	}

	rc = kvm_init(sizeof(struct kvm_vcpu), 0, THIS_MODULE);
	if (rc)
		goto err_unregister_cpu_pm;

	if (kvm_riscv_aia_available())
		kvm_info("AIA available with %d guest external interrupts\n",
			 atomic_read(&kvm_riscv_aia_nr_hgei));

	return 0;

err_unregister_cpu_pm:
	if (IS_ENABLED(CONFIG_CPU_PM))
		cpu_pm_unregister_notifier(&kvm_riscv_cpu_pm_nb);
err_teardown:
	kvm_riscv_teardown();
	return rc;
}
module_init(riscv_kvm_init);

static void __exit riscv_kvm_exit(void)
{
	kvm_exit();

	/* Unregister CPU PM notifier */
	if (IS_ENABLED(CONFIG_CPU_PM))
		cpu_pm_unregister_notifier(&kvm_riscv_cpu_pm_nb);

	kvm_riscv_teardown();
}
module_exit(riscv_kvm_exit);