accel/accel-irq: add generic begin_route_changes

A generic accel_irqchip_begin_route_change() fn has been introduced for
usage in the MSHV accelerator. It replaces the respective kvm_ fn.

Signed-off-by: Magnus Kulke <magnuskulke@linux.microsoft.com>
Link: https://lore.kernel.org/r/20260417105618.3621-6-magnuskulke@linux.microsoft.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

accel/accel-irq.c

@@ -10,6 +10,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/error-report.h"
 #include "hw/pci/msi.h"
 
 #include "system/kvm.h"
@@ -104,3 +105,23 @@ int accel_irqchip_remove_irqfd_notifier_gsi(EventNotifier *n, int virq)
     }
     return -ENOSYS;
 }
+
+inline AccelRouteChange accel_irqchip_begin_route_changes(void)
+{
+#ifdef CONFIG_MSHV_IS_POSSIBLE
+    if (mshv_msi_via_irqfd_enabled()) {
+        return (AccelRouteChange) {
+            .accel = ACCEL(mshv_state),
+            .changes = 0,
+        };
+    }
+#endif
+    if (kvm_enabled()) {
+        return (AccelRouteChange) {
+            .accel = ACCEL(kvm_state),
+            .changes = 0,
+        };
+    }
+    error_report("can't initiate route change, no accel irqchip available");
+    abort();
+}

hw/misc/ivshmem-pci.c

@@ -26,7 +26,7 @@
 #include "hw/core/qdev-properties-system.h"
 #include "hw/pci/msi.h"
 #include "hw/pci/msix.h"
-#include "system/kvm.h"
+#include "system/accel-irq.h"
 #include "migration/blocker.h"
 #include "migration/vmstate.h"
 #include "qemu/error-report.h"
@@ -430,7 +430,7 @@ static void ivshmem_add_kvm_msi_virq(IVShmemState *s, int vector,
     IVSHMEM_DPRINTF("ivshmem_add_kvm_msi_virq vector:%d\n", vector);
     assert(!s->msi_vectors[vector].pdev);
 
-    c = kvm_irqchip_begin_route_changes(kvm_state);
+    c = accel_irqchip_begin_route_changes();
     ret = kvm_irqchip_add_msi_route(&c, vector, pdev);
     if (ret < 0) {
         error_setg(errp, "kvm_irqchip_add_msi_route failed");

hw/vfio/pci.c

@@ -38,6 +38,7 @@
 #include "qemu/module.h"
 #include "qemu/range.h"
 #include "qemu/units.h"
+#include "system/accel-irq.h"
 #include "system/kvm.h"
 #include "system/runstate.h"
 #include "pci.h"
@@ -688,7 +689,7 @@ static int vfio_msix_vector_do_use(PCIDevice *pdev, unsigned int nr,
             if (vdev->defer_kvm_irq_routing) {
                 vfio_pci_add_kvm_msi_virq(vdev, vector, nr, true);
             } else {
-                vfio_route_change = kvm_irqchip_begin_route_changes(kvm_state);
+                vfio_route_change = accel_irqchip_begin_route_changes();
                 vfio_pci_add_kvm_msi_virq(vdev, vector, nr, true);
                 kvm_irqchip_commit_route_changes(&vfio_route_change);
                 vfio_connect_kvm_msi_virq(vector, nr);
@@ -789,7 +790,7 @@ void vfio_pci_prepare_kvm_msi_virq_batch(VFIOPCIDevice *vdev)
 {
     assert(!vdev->defer_kvm_irq_routing);
     vdev->defer_kvm_irq_routing = true;
-    vfio_route_change = kvm_irqchip_begin_route_changes(kvm_state);
+    vfio_route_change = accel_irqchip_begin_route_changes();
 }
 
 void vfio_pci_commit_kvm_msi_virq_batch(VFIOPCIDevice *vdev)

hw/virtio/virtio-pci.c

@@ -869,7 +869,7 @@ static int kvm_virtio_pci_vq_vector_use(VirtIOPCIProxy *proxy,
     int ret;
 
     if (irqfd->users == 0) {
-        AccelRouteChange c = kvm_irqchip_begin_route_changes(kvm_state);
+        AccelRouteChange c = accel_irqchip_begin_route_changes();
         ret = accel_irqchip_add_msi_route(&c, vector, &proxy->pci_dev);
         if (ret < 0) {
             return ret;

include/system/accel-irq.h

@@ -25,6 +25,7 @@ static inline bool accel_irqchip_is_split(void)
     return mshv_msi_via_irqfd_enabled() || kvm_irqchip_is_split();
 }
 
+AccelRouteChange accel_irqchip_begin_route_changes(void);
 int accel_irqchip_add_msi_route(AccelRouteChange *c, int vector,
                                 PCIDevice *dev);
 int accel_irqchip_update_msi_route(int vector, MSIMessage msg, PCIDevice *dev);

include/system/kvm.h

@@ -476,14 +476,6 @@ int kvm_irqchip_update_msi_route(KVMState *s, int virq, MSIMessage msg,
                                  PCIDevice *dev);
 void kvm_irqchip_commit_routes(KVMState *s);
 
-static inline AccelRouteChange kvm_irqchip_begin_route_changes(KVMState *s)
-{
-    return (AccelRouteChange) {
-        .accel = ACCEL(s),
-        .changes = 0,
-    };
-}
-
 static inline void kvm_irqchip_commit_route_changes(AccelRouteChange *c)
 {
     if (c->changes) {

target/i386/kvm/kvm.c

@@ -32,6 +32,7 @@
 #include "vmsr_energy.h"
 #include "system/system.h"
 #include "system/hw_accel.h"
+#include "system/accel-irq.h"
 #include "system/kvm_int.h"
 #include "system/runstate.h"
 #include "system/ramblock.h"
@@ -6678,7 +6679,7 @@ void kvm_arch_init_irq_routing(KVMState *s)
     kvm_gsi_routing_allowed = true;
 
     if (kvm_irqchip_is_split()) {
-        AccelRouteChange c = kvm_irqchip_begin_route_changes(s);
+        AccelRouteChange c = accel_irqchip_begin_route_changes();
         int i;
 
         /* If the ioapic is in QEMU and the lapics are in KVM, reserve