diff --git a/hw/vfio_pci.c b/hw/vfio_pci.c
index 7c27834..5178ccc 100644
--- a/hw/vfio_pci.c
+++ b/hw/vfio_pci.c
@@ -561,8 +561,9 @@ static int vfio_enable_vectors(VFIODevice *vdev, bool msix)
     return ret;
 }
 
-static int vfio_msix_vector_use(PCIDevice *pdev,
-                                unsigned int nr, MSIMessage msg)
+static int vfio_msix_vector_do_use(PCIDevice *pdev, unsigned int nr,
+                                   MSIMessage msg, bool try_kvm,
+                                   IOHandler *handler)
 {
     VFIODevice *vdev = DO_UPCAST(VFIODevice, pdev, pdev);
     VFIOMSIVector *vector;
@@ -586,7 +587,7 @@ static int vfio_msix_vector_use(PCIDevice *pdev,
      * Attempt to enable route through KVM irqchip,
      * default to userspace handling if unavailable.
      */
-    vector->virq = kvm_irqchip_add_msi_route(kvm_state, msg);
+    vector->virq = try_kvm ? kvm_irqchip_add_msi_route(kvm_state, msg) : -1;
     if (vector->virq < 0 ||
         kvm_irqchip_add_irqfd_notifier(kvm_state, &vector->interrupt,
                                        vector->virq) < 0) {
@@ -595,7 +596,7 @@ static int vfio_msix_vector_use(PCIDevice *pdev,
             vector->virq = -1;
         }
         qemu_set_fd_handler(event_notifier_get_fd(&vector->interrupt),
-                            vfio_msi_interrupt, NULL, vector);
+                            handler, NULL, vector);
     }
 
     /*
@@ -638,6 +639,12 @@ static int vfio_msix_vector_use(PCIDevice *pdev,
     return 0;
 }
 
+static int vfio_msix_vector_use(PCIDevice *pdev,
+                                unsigned int nr, MSIMessage msg)
+{
+    return vfio_msix_vector_do_use(pdev, nr, msg, true, vfio_msi_interrupt);
+}
+
 static void vfio_msix_vector_release(PCIDevice *pdev, unsigned int nr)
 {
     VFIODevice *vdev = DO_UPCAST(VFIODevice, pdev, pdev);
@@ -696,6 +703,22 @@ static void vfio_enable_msix(VFIODevice *vdev)
 
     vdev->interrupt = VFIO_INT_MSIX;
 
+    /*
+     * Some communication channels between VF & PF or PF & fw rely on the
+     * physical state of the device and expect that enabling MSI-X from the
+     * guest enables the same on the host.  When our guest is Linux, the
+     * guest driver call to pci_enable_msix() sets the enabling bit in the
+     * MSI-X capability, but leaves the vector table masked.  We therefore
+     * can't rely on a vector_use callback (from request_irq() in the guest)
+     * to switch the physical device into MSI-X mode because that may come a
+     * long time after pci_enable_msix().  This code enables vector 0 with
+     * triggering to userspace, then immediately release the vector, leaving
+     * the physical device with no vectors enabled, but MSI-X enabled, just
+     * like the guest view.
+     */
+    vfio_msix_vector_do_use(&vdev->pdev, 0, (MSIMessage) { 0, 0 }, false, NULL);
+    vfio_msix_vector_release(&vdev->pdev, 0);
+
     if (msix_set_vector_notifiers(&vdev->pdev, vfio_msix_vector_use,
                                   vfio_msix_vector_release)) {
         error_report("vfio: msix_set_vector_notifiers failed\n");