pci-assign: Use PCI-2.3-based shared legacy interrupts

index 5f5bde1..30e05f1 100644
@@ -404,12 +404,18 @@ static uint8_t pci_find_cap_offset(PCIDevice *d, uint8_t cap)
     return 0;
 }
 
+static uint32_t calc_assigned_dev_id(uint16_t seg, uint8_t bus, uint8_t devfn)
+{
+    return (uint32_t)seg << 16 | (uint32_t)bus << 8 | (uint32_t)devfn;
+}
+
 static void assigned_dev_pci_write_config(PCIDevice *d, uint32_t address,
                                           uint32_t val, int len)
 {
     int fd;
     ssize_t ret;
     AssignedDevice *pci_dev = container_of(d, AssignedDevice, dev);
+    struct kvm_assigned_pci_dev assigned_dev_data;
 
     DEBUG("(%x.%x): address=%04x val=0x%08x len=%d\n",
           ((d->devfn >> 3) & 0x1F), (d->devfn & 0x7),

@@ -417,6 +423,17 @@ static void assigned_dev_pci_write_config(PCIDevice *d, uint32_t address,
 
     if (address == 0x4) {
         pci_default_write_config(d, address, val, len);
+        pci_dev->intx_masked = val & PCI_COMMAND_INTX_DISABLE;
+#ifdef KVM_CAP_PCI_2_3
+        memset(&assigned_dev_data, 0, sizeof(assigned_dev_data));
+        assigned_dev_data.assigned_dev_id  =
+            calc_assigned_dev_id(pci_dev->h_segnr, pci_dev->h_busnr,
+                                 pci_dev->h_devfn);
+        if (pci_dev->intx_masked) {
+            assigned_dev_data.flags = KVM_DEV_ASSIGN_MASK_INTX;
+        }
+        kvm_assign_set_intx_mask(kvm_context, &assigned_dev_data);
+#endif
         /* Continue to program the card */
     }
 

@@ -494,6 +511,10 @@ do_log:
         else if (address == 6)
             val &= ~0x10;
     }
+    if (address == PCI_COMMAND) {
+        val &= ~PCI_COMMAND_INTX_DISABLE;
+        val |= pci_dev->intx_masked;
+    }
 
     return val;
 }

@@ -824,11 +845,6 @@ static void free_assigned_device(AssignedDevice *dev)
     }
 }
 
-static uint32_t calc_assigned_dev_id(uint16_t seg, uint8_t bus, uint8_t devfn)
-{
-    return (uint32_t)seg << 16 | (uint32_t)bus << 8 | (uint32_t)devfn;
-}
-
 static void assign_failed_examine(AssignedDevice *dev)
 {
     char name[PATH_MAX], dir[PATH_MAX], driver[PATH_MAX] = {}, *ns;

@@ -919,6 +935,11 @@ static int assign_device(AssignedDevice *dev)
                 "cause host memory corruption if the device issues DMA write "
                 "requests!\n");
     }
+#ifdef KVM_CAP_PCI_2_3
+    if (dev->features & ASSIGNED_DEVICE_USE_PCI_2_3_MASK) {
+        assigned_dev_data.flags |= KVM_DEV_ASSIGN_PCI_2_3;
+    }
+#endif /* KVM_CAP_PCI_2_3 */
 
     r = kvm_assign_pci_device(kvm_context, &assigned_dev_data);
     if (r < 0) {

@@ -981,8 +1002,8 @@ static int assign_irq(AssignedDevice *dev)
     if (r < 0) {
         fprintf(stderr, "Failed to assign irq for \"%s\": %s\n",
                 dev->dev.qdev.id, strerror(-r));
-        fprintf(stderr, "Perhaps you are assigning a device "
-                "that shares an IRQ with another device?\n");
+        fprintf(stderr, "If the assigned device shares an IRQ with another "
+                "device, try host_pci_2_3=on.\n");
         return r;
     }
 

@@ -1554,6 +1575,8 @@ static PCIDeviceInfo assign_info = {
                         ASSIGNED_DEVICE_USE_IOMMU_BIT, true),
         DEFINE_PROP_BIT("prefer_msi", AssignedDevice, features,
                         ASSIGNED_DEVICE_PREFER_MSI_BIT, true),
+        DEFINE_PROP_BIT("host_pci_2_3", AssignedDevice, features,
+                        ASSIGNED_DEVICE_USE_PCI_2_3_BIT, false),
         DEFINE_PROP_STRING("configfd", AssignedDevice, configfd_name),
         DEFINE_PROP_END_OF_LIST(),
     },

index c94a730..71ba94c 100644
@@ -76,15 +76,18 @@ typedef struct {
 
 #define ASSIGNED_DEVICE_USE_IOMMU_BIT	0
 #define ASSIGNED_DEVICE_PREFER_MSI_BIT	1
+#define ASSIGNED_DEVICE_USE_PCI_2_3_BIT	2
 
 #define ASSIGNED_DEVICE_USE_IOMMU_MASK	(1 << ASSIGNED_DEVICE_USE_IOMMU_BIT)
 #define ASSIGNED_DEVICE_PREFER_MSI_MASK	(1 << ASSIGNED_DEVICE_PREFER_MSI_BIT)
+#define ASSIGNED_DEVICE_USE_PCI_2_3_MASK (1 << ASSIGNED_DEVICE_USE_PCI_2_3_BIT)
 
 typedef struct AssignedDevice {
     PCIDevice dev;
     PCIHostDevice host;
     uint32_t features;
     int intpin;
+    uint32_t intx_masked;
     uint8_t debug_flags;
     AssignedDevRegion v_addrs[PCI_NUM_REGIONS - 1];
     PCIDevRegions real_device;

index 471306b..8157b4f 100644
@@ -740,6 +740,14 @@ int kvm_deassign_pci_device(kvm_context_t kvm,
 }
 #endif
 
+#ifdef KVM_CAP_PCI_2_3
+int kvm_assign_set_intx_mask(kvm_context_t kvm,
+                             struct kvm_assigned_pci_dev *assigned_dev)
+{
+    return kvm_vm_ioctl(kvm_state, KVM_ASSIGN_SET_INTX_MASK, assigned_dev);
+}
+#endif
+
 int kvm_reinject_control(kvm_context_t kvm, int pit_reinject)
 {
 #ifdef KVM_CAP_REINJECT_CONTROL

index 0f3fb50..7f26f1a 100644
@@ -631,6 +631,9 @@ int kvm_assign_set_msix_entry(kvm_context_t kvm,
                               struct kvm_assigned_msix_entry *entry);
 #endif
 
+int kvm_assign_set_intx_mask(kvm_context_t kvm,
+                             struct kvm_assigned_pci_dev *assigned_dev);
+
 #else                           /* !CONFIG_KVM */
 
 typedef struct kvm_context *kvm_context_t;