[PATCH 5/8] i386/kvm: Use x86_iommu_device_get() for per-device IOMMU lookup

[Sairaj Kodilkar <sarunkod@amd.com>]

Currently, kvm_arch_fixup_msi_route() unconditionally uses the default
system IOMMU for interrupt remapping when IOMMU is present. This
approach fails when an IOMMU is attached to a non-system bus and serves
only a subset of devices, because the kernel does not program IRT
(Interrupt Remapping Table) entries for devices outside the IOMMU's
scope.

This patch changes the behavior to perform per-device IOMMU lookup:
- For PCI devices: Use pci_device_get_x86_iommu() to find the specific
  IOMMU serving that device, if any
- For non-PCI devices (IOAPIC): Fall back to the default IOMMU
  only if interrupt remapping is enabled (ioapic_as != address_space_memory)

This ensures MSI route translation occurs only for devices actually
managed by an IOMMU, enabling proper interrupt remapping in configurations
where IOMMUs are attached to arbitrary buses.

NOTE: This patch assumes that only non-PCI device calling is IOAPIC and
checks ioapic_as to determine interrupt remapping.

Signed-off-by: Sairaj Kodilkar <sarunkod@amd.com>
---
 hw/intc/ioapic.c      |  3 ++-
 target/i386/kvm/kvm.c | 15 ++++++++++++---
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/hw/intc/ioapic.c b/hw/intc/ioapic.c
index 1b3f1e824ac4..f1b881ee6118 100644
--- a/hw/intc/ioapic.c
+++ b/hw/intc/ioapic.c
@@ -438,8 +438,9 @@ static void ioapic_machine_done_notify(Notifier *notifier, void *data)
 #ifdef ACCEL_GSI_IRQFD_POSSIBLE
     IOAPICCommonState *s = container_of(notifier, IOAPICCommonState,
                                         machine_done);
+    X86MachineState *x86ms = X86_MACHINE(qdev_get_machine());
 
-    if (accel_irqchip_is_split()) {
+    if (accel_irqchip_is_split() && x86ms->ioapic_as != &address_space_memory) {
         X86IOMMUState *iommu = x86_iommu_get_default();
         if (iommu) {
             /* Register this IOAPIC with IOMMU IEC notifier, so that
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 644c45fb0a02..ffe977ceb418 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -6746,7 +6746,15 @@ uint64_t kvm_swizzle_msi_ext_dest_id(uint64_t address)
 int kvm_arch_fixup_msi_route(struct kvm_irq_routing_entry *route,
                              uint64_t address, uint32_t data, PCIDevice *dev)
 {
-    X86IOMMUState *iommu = x86_iommu_get_default();
+    X86IOMMUState *iommu = NULL;
+    MachineState *ms = MACHINE(qdev_get_machine());
+    X86MachineState *x86ms = X86_MACHINE(ms);
+
+    if (dev) {
+        iommu = x86_iommu_device_get(dev);
+    } else if (x86ms->ioapic_as != &address_space_memory) {
+        iommu = x86_iommu_get_default();
+    }
 
     if (iommu) {
         X86IOMMUClass *class = X86_IOMMU_DEVICE_GET_CLASS(iommu);
@@ -6848,6 +6856,7 @@ int kvm_arch_add_msi_route_post(struct kvm_irq_routing_entry *route,
 {
     static bool notify_list_inited = false;
     MSIRouteEntry *entry;
+    X86IOMMUState *iommu = NULL;
 
     if (!dev) {
         /* These are (possibly) IOAPIC routes only used for split
@@ -6867,13 +6876,13 @@ int kvm_arch_add_msi_route_post(struct kvm_irq_routing_entry *route,
     if (!notify_list_inited) {
         /* For the first time we do add route, add ourselves into
          * IOMMU's IEC notify list if needed. */
-        X86IOMMUState *iommu = x86_iommu_get_default();
+        iommu = x86_iommu_device_get(dev);
         if (iommu) {
             x86_iommu_iec_register_notifier(iommu,
                                             kvm_update_msi_routes_all,
                                             NULL);
+            notify_list_inited = true;
         }
-        notify_list_inited = true;
     }
     return 0;
 }
-- 
2.34.1