LoongArch: KVM: Add irqfd support

Enable the KVM_IRQ_ROUTING/KVM_IRQCHIP/KVM_MSI configuration items,
add the KVM_CAP_IRQCHIP capability, and implement the query interface
of the in-kernel irqchip.

Signed-off-by: Xianglai Li <lixianglai@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/kvm/irqfd.c

@@ -0,0 +1,89 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2024 Loongson Technology Corporation Limited
+ */
+
+#include <linux/kvm_host.h>
+#include <trace/events/kvm.h>
+#include <asm/kvm_pch_pic.h>
+
+static int kvm_set_pic_irq(struct kvm_kernel_irq_routing_entry *e,
+		struct kvm *kvm, int irq_source_id, int level, bool line_status)
+{
+	/* PCH-PIC pin (0 ~ 64) <---> GSI (0 ~ 64) */
+	pch_pic_set_irq(kvm->arch.pch_pic, e->irqchip.pin, level);
+
+	return 0;
+}
+
+/*
+ * kvm_set_msi: inject the MSI corresponding to the
+ * MSI routing entry
+ *
+ * This is the entry point for irqfd MSI injection
+ * and userspace MSI injection.
+ */
+int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
+		struct kvm *kvm, int irq_source_id, int level, bool line_status)
+{
+	if (!level)
+		return -1;
+
+	pch_msi_set_irq(kvm, e->msi.data, level);
+
+	return 0;
+}
+
+/*
+ * kvm_set_routing_entry: populate a kvm routing entry
+ * from a user routing entry
+ *
+ * @kvm: the VM this entry is applied to
+ * @e: kvm kernel routing entry handle
+ * @ue: user api routing entry handle
+ * return 0 on success, -EINVAL on errors.
+ */
+int kvm_set_routing_entry(struct kvm *kvm,
+			struct kvm_kernel_irq_routing_entry *e,
+			const struct kvm_irq_routing_entry *ue)
+{
+	switch (ue->type) {
+	case KVM_IRQ_ROUTING_IRQCHIP:
+		e->set = kvm_set_pic_irq;
+		e->irqchip.irqchip = ue->u.irqchip.irqchip;
+		e->irqchip.pin = ue->u.irqchip.pin;
+
+		if (e->irqchip.pin >= KVM_IRQCHIP_NUM_PINS)
+			return -EINVAL;
+
+		return 0;
+	case KVM_IRQ_ROUTING_MSI:
+		e->set = kvm_set_msi;
+		e->msi.address_lo = ue->u.msi.address_lo;
+		e->msi.address_hi = ue->u.msi.address_hi;
+		e->msi.data = ue->u.msi.data;
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+int kvm_arch_set_irq_inatomic(struct kvm_kernel_irq_routing_entry *e,
+		struct kvm *kvm, int irq_source_id, int level, bool line_status)
+{
+	switch (e->type) {
+	case KVM_IRQ_ROUTING_IRQCHIP:
+		pch_pic_set_irq(kvm->arch.pch_pic, e->irqchip.pin, level);
+		return 0;
+	case KVM_IRQ_ROUTING_MSI:
+		pch_msi_set_irq(kvm, e->msi.data, level);
+		return 0;
+	default:
+		return -EWOULDBLOCK;
+	}
+}
+
+bool kvm_arch_intc_initialized(struct kvm *kvm)
+{
+	return kvm_arch_irqchip_in_kernel(kvm);
+}