KVM: x86: Move IRQ mask notifier infrastructure to I/O APIC emulation

Move the IRQ mask logic to ioapic.c as KVM's only user is its in-kernel
I/O APIC emulation.  In addition to encapsulating more I/O APIC specific
code, trimming down irq_comm.c helps pave the way for removing it entirely.

Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20250611213557.294358-18-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: sean-jc

arch/x86/include/asm/kvm_host.h

@@ -1427,9 +1427,6 @@ struct kvm_arch {
 	struct delayed_work kvmclock_update_work;
 	struct delayed_work kvmclock_sync_work;
 
-	/* reads protected by irq_srcu, writes by irq_lock */
-	struct hlist_head mask_notifier_list;
-
 #ifdef CONFIG_KVM_HYPERV
 	struct kvm_hv hyperv;
 #endif
@@ -2039,19 +2036,6 @@ int load_pdptrs(struct kvm_vcpu *vcpu, unsigned long cr3);
 int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa,
 			  const void *val, int bytes);
 
-struct kvm_irq_mask_notifier {
-	void (*func)(struct kvm_irq_mask_notifier *kimn, bool masked);
-	int irq;
-	struct hlist_node link;
-};
-
-void kvm_register_irq_mask_notifier(struct kvm *kvm, int irq,
-				    struct kvm_irq_mask_notifier *kimn);
-void kvm_unregister_irq_mask_notifier(struct kvm *kvm, int irq,
-				      struct kvm_irq_mask_notifier *kimn);
-void kvm_fire_mask_notifiers(struct kvm *kvm, unsigned irqchip, unsigned pin,
-			     bool mask);
-
 extern bool tdp_enabled;
 
 u64 vcpu_tsc_khz(struct kvm_vcpu *vcpu);

arch/x86/kvm/i8254.h

@@ -8,6 +8,8 @@
 
 #include <uapi/asm/kvm.h>
 
+#include "ioapic.h"
+
 #ifdef CONFIG_KVM_IOAPIC
 struct kvm_kpit_channel_state {
 	u32 count; /* can be 65536 */

arch/x86/kvm/i8259.c

@@ -31,6 +31,8 @@
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/bitops.h>
+
+#include "ioapic.h"
 #include "irq.h"
 
 #include <linux/kvm_host.h>

arch/x86/kvm/ioapic.c

@@ -310,6 +310,42 @@ void kvm_arch_post_irq_ack_notifier_list_update(struct kvm *kvm)
 	kvm_make_scan_ioapic_request(kvm);
 }
 
+void kvm_register_irq_mask_notifier(struct kvm *kvm, int irq,
+				    struct kvm_irq_mask_notifier *kimn)
+{
+	struct kvm_ioapic *ioapic = kvm->arch.vioapic;
+
+	mutex_lock(&kvm->irq_lock);
+	kimn->irq = irq;
+	hlist_add_head_rcu(&kimn->link, &ioapic->mask_notifier_list);
+	mutex_unlock(&kvm->irq_lock);
+}
+
+void kvm_unregister_irq_mask_notifier(struct kvm *kvm, int irq,
+				      struct kvm_irq_mask_notifier *kimn)
+{
+	mutex_lock(&kvm->irq_lock);
+	hlist_del_rcu(&kimn->link);
+	mutex_unlock(&kvm->irq_lock);
+	synchronize_srcu(&kvm->irq_srcu);
+}
+
+void kvm_fire_mask_notifiers(struct kvm *kvm, unsigned irqchip, unsigned pin,
+			     bool mask)
+{
+	struct kvm_ioapic *ioapic = kvm->arch.vioapic;
+	struct kvm_irq_mask_notifier *kimn;
+	int idx, gsi;
+
+	idx = srcu_read_lock(&kvm->irq_srcu);
+	gsi = kvm_irq_map_chip_pin(kvm, irqchip, pin);
+	if (gsi != -1)
+		hlist_for_each_entry_rcu(kimn, &ioapic->mask_notifier_list, link)
+			if (kimn->irq == gsi)
+				kimn->func(kimn, mask);
+	srcu_read_unlock(&kvm->irq_srcu, idx);
+}
+
 static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val)
 {
 	unsigned index;
@@ -710,6 +746,7 @@ int kvm_ioapic_init(struct kvm *kvm)
 		return -ENOMEM;
 	spin_lock_init(&ioapic->lock);
 	INIT_DELAYED_WORK(&ioapic->eoi_inject, kvm_ioapic_eoi_inject_work);
+	INIT_HLIST_HEAD(&ioapic->mask_notifier_list);
 	kvm->arch.vioapic = ioapic;
 	kvm_ioapic_reset(ioapic);
 	kvm_iodevice_init(&ioapic->dev, &ioapic_mmio_ops);

arch/x86/kvm/ioapic.h

@@ -86,8 +86,24 @@ struct kvm_ioapic {
 	struct delayed_work eoi_inject;
 	u32 irq_eoi[IOAPIC_NUM_PINS];
 	u32 irr_delivered;
+
+	/* reads protected by irq_srcu, writes by irq_lock */
+	struct hlist_head mask_notifier_list;
+};
+
+struct kvm_irq_mask_notifier {
+	void (*func)(struct kvm_irq_mask_notifier *kimn, bool masked);
+	int irq;
+	struct hlist_node link;
 };
 
+void kvm_register_irq_mask_notifier(struct kvm *kvm, int irq,
+				    struct kvm_irq_mask_notifier *kimn);
+void kvm_unregister_irq_mask_notifier(struct kvm *kvm, int irq,
+				      struct kvm_irq_mask_notifier *kimn);
+void kvm_fire_mask_notifiers(struct kvm *kvm, unsigned irqchip, unsigned pin,
+			     bool mask);
+
 #ifdef DEBUG
 #define ASSERT(x)  							\
 do {									\

arch/x86/kvm/irq_comm.c

@@ -161,39 +161,6 @@ int kvm_arch_set_irq_inatomic(struct kvm_kernel_irq_routing_entry *e,
 	return -EWOULDBLOCK;
 }
 
-void kvm_register_irq_mask_notifier(struct kvm *kvm, int irq,
-				    struct kvm_irq_mask_notifier *kimn)
-{
-	mutex_lock(&kvm->irq_lock);
-	kimn->irq = irq;
-	hlist_add_head_rcu(&kimn->link, &kvm->arch.mask_notifier_list);
-	mutex_unlock(&kvm->irq_lock);
-}
-
-void kvm_unregister_irq_mask_notifier(struct kvm *kvm, int irq,
-				      struct kvm_irq_mask_notifier *kimn)
-{
-	mutex_lock(&kvm->irq_lock);
-	hlist_del_rcu(&kimn->link);
-	mutex_unlock(&kvm->irq_lock);
-	synchronize_srcu(&kvm->irq_srcu);
-}
-
-void kvm_fire_mask_notifiers(struct kvm *kvm, unsigned irqchip, unsigned pin,
-			     bool mask)
-{
-	struct kvm_irq_mask_notifier *kimn;
-	int idx, gsi;
-
-	idx = srcu_read_lock(&kvm->irq_srcu);
-	gsi = kvm_irq_map_chip_pin(kvm, irqchip, pin);
-	if (gsi != -1)
-		hlist_for_each_entry_rcu(kimn, &kvm->arch.mask_notifier_list, link)
-			if (kimn->irq == gsi)
-				kimn->func(kimn, mask);
-	srcu_read_unlock(&kvm->irq_srcu, idx);
-}
-
 bool kvm_arch_can_set_irq_routing(struct kvm *kvm)
 {
 	return irqchip_in_kernel(kvm);

arch/x86/kvm/x86.c

@@ -12676,7 +12676,6 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 	if (ret)
 		goto out_uninit_mmu;
 
-	INIT_HLIST_HEAD(&kvm->arch.mask_notifier_list);
 	atomic_set(&kvm->arch.noncoherent_dma_count, 0);
 
 	raw_spin_lock_init(&kvm->arch.tsc_write_lock);