LoongArch: KVM: Implement VM related functions

Implement LoongArch VM operations: Init and destroy vm interface,
allocating memory page to save the vm pgd when init vm. Implement
vm check extension, such as getting vcpu number info, memory slots
info, and fpu info. And implement vm status description.
Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Tested-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/kvm/vm.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020-2023 Loongson Technology Corporation Limited
+ */
+
+#include <linux/kvm_host.h>
+#include <asm/kvm_mmu.h>
+
+const struct _kvm_stats_desc kvm_vm_stats_desc[] = {
+	KVM_GENERIC_VM_STATS(),
+	STATS_DESC_ICOUNTER(VM, pages),
+	STATS_DESC_ICOUNTER(VM, hugepages),
+};
+
+const struct kvm_stats_header kvm_vm_stats_header = {
+	.name_size = KVM_STATS_NAME_SIZE,
+	.num_desc = ARRAY_SIZE(kvm_vm_stats_desc),
+	.id_offset =  sizeof(struct kvm_stats_header),
+	.desc_offset = sizeof(struct kvm_stats_header) + KVM_STATS_NAME_SIZE,
+	.data_offset = sizeof(struct kvm_stats_header) + KVM_STATS_NAME_SIZE +
+					sizeof(kvm_vm_stats_desc),
+};
+
+int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
+{
+	int i;
+
+	/* Allocate page table to map GPA -> RPA */
+	kvm->arch.pgd = kvm_pgd_alloc();
+	if (!kvm->arch.pgd)
+		return -ENOMEM;
+
+	kvm_init_vmcs(kvm);
+	kvm->arch.gpa_size = BIT(cpu_vabits - 1);
+	kvm->arch.root_level = CONFIG_PGTABLE_LEVELS - 1;
+	kvm->arch.invalid_ptes[0] = 0;
+	kvm->arch.invalid_ptes[1] = (unsigned long)invalid_pte_table;
+#if CONFIG_PGTABLE_LEVELS > 2
+	kvm->arch.invalid_ptes[2] = (unsigned long)invalid_pmd_table;
+#endif
+#if CONFIG_PGTABLE_LEVELS > 3
+	kvm->arch.invalid_ptes[3] = (unsigned long)invalid_pud_table;
+#endif
+	for (i = 0; i <= kvm->arch.root_level; i++)
+		kvm->arch.pte_shifts[i] = PAGE_SHIFT + i * (PAGE_SHIFT - 3);
+
+	return 0;
+}
+
+void kvm_arch_destroy_vm(struct kvm *kvm)
+{
+	kvm_destroy_vcpus(kvm);
+	free_page((unsigned long)kvm->arch.pgd);
+	kvm->arch.pgd = NULL;
+}
+
+int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
+{
+	int r;
+
+	switch (ext) {
+	case KVM_CAP_ONE_REG:
+	case KVM_CAP_ENABLE_CAP:
+	case KVM_CAP_READONLY_MEM:
+	case KVM_CAP_SYNC_MMU:
+	case KVM_CAP_IMMEDIATE_EXIT:
+	case KVM_CAP_IOEVENTFD:
+	case KVM_CAP_MP_STATE:
+		r = 1;
+		break;
+	case KVM_CAP_NR_VCPUS:
+		r = num_online_cpus();
+		break;
+	case KVM_CAP_MAX_VCPUS:
+		r = KVM_MAX_VCPUS;
+		break;
+	case KVM_CAP_MAX_VCPU_ID:
+		r = KVM_MAX_VCPU_IDS;
+		break;
+	case KVM_CAP_NR_MEMSLOTS:
+		r = KVM_USER_MEM_SLOTS;
+		break;
+	default:
+		r = 0;
+		break;
+	}
+
+	return r;
+}
+
+int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
+{
+	return -ENOIOCTLCMD;
+}