Merge tag 'for_upstream' of https://git.kernel.org/pub/scm/virt/kvm/m…

…st/qemu into staging

virtio: bugfix

A last minute fix for a use of a vector after it's released.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

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* tag 'for_upstream' of https://git.kernel.org/pub/scm/virt/kvm/mst/qemu:
  virtio-pci: fix use of a released vector

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/virtio/virtio-pci.c

@@ -1424,6 +1424,38 @@ static int virtio_pci_add_mem_cap(VirtIOPCIProxy *proxy,
     return offset;
 }
 
+static void virtio_pci_set_vector(VirtIODevice *vdev,
+                                  VirtIOPCIProxy *proxy,
+                                  int queue_no, uint16_t old_vector,
+                                  uint16_t new_vector)
+{
+    bool kvm_irqfd = (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
+        msix_enabled(&proxy->pci_dev) && kvm_msi_via_irqfd_enabled();
+
+    if (new_vector == old_vector) {
+        return;
+    }
+
+    /*
+     * If the device uses irqfd and the vector changes after DRIVER_OK is
+     * set, we need to release the old vector and set up the new one.
+     * Otherwise just need to set the new vector on the device.
+     */
+    if (kvm_irqfd && old_vector != VIRTIO_NO_VECTOR) {
+        kvm_virtio_pci_vector_release_one(proxy, queue_no);
+    }
+    /* Set the new vector on the device. */
+    if (queue_no == VIRTIO_CONFIG_IRQ_IDX) {
+        vdev->config_vector = new_vector;
+    } else {
+        virtio_queue_set_vector(vdev, queue_no, new_vector);
+    }
+    /* If the new vector changed need to set it up. */
+    if (kvm_irqfd && new_vector != VIRTIO_NO_VECTOR) {
+        kvm_virtio_pci_vector_use_one(proxy, queue_no);
+    }
+}
+
 int virtio_pci_add_shm_cap(VirtIOPCIProxy *proxy,
                            uint8_t bar, uint64_t offset, uint64_t length,
                            uint8_t id)
@@ -1570,7 +1602,8 @@ static void virtio_pci_common_write(void *opaque, hwaddr addr,
         } else {
             val = VIRTIO_NO_VECTOR;
         }
-        vdev->config_vector = val;
+        virtio_pci_set_vector(vdev, proxy, VIRTIO_CONFIG_IRQ_IDX,
+                              vdev->config_vector, val);
         break;
     case VIRTIO_PCI_COMMON_STATUS:
         if (!(val & VIRTIO_CONFIG_S_DRIVER_OK)) {
@@ -1610,7 +1643,7 @@ static void virtio_pci_common_write(void *opaque, hwaddr addr,
         } else {
             val = VIRTIO_NO_VECTOR;
         }
-        virtio_queue_set_vector(vdev, vdev->queue_sel, val);
+        virtio_pci_set_vector(vdev, proxy, vdev->queue_sel, vector, val);
         break;
     case VIRTIO_PCI_COMMON_Q_ENABLE:
         if (val == 1) {