virtio: improve virtqueue mapping error messages

Improve error reporting when virtqueue ring mapping fails by including a
device identifier in the error message.

Introduce a helper qdev_get_printable_name() in qdev-core, which returns
either:

 - the device ID, if explicitly provided (e.g. -device ...,id=foo)
 - the QOM path from qdev_get_dev_path(dev) otherwise
 - "<unknown device>" as a fallback when no identifier is present

This makes it easier to identify which device triggered the error in
multi-device setups or when debugging complex guest configurations.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/230
Buglink: https://bugs.launchpad.net/qemu/+bug/1919021
Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Alessandro Ratti <alessandro@0x65c.net>
Message-Id: <20250924093138.559872-2-alessandro@0x65c.net>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 12 insertions, 3 deletions

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index de89e8104a..d38aafe5eb 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -257,7 +257,10 @@ void virtio_init_region_cache(VirtIODevice *vdev, int n)
     len = address_space_cache_init(&new->desc, vdev->dma_as,
                                    addr, size, packed);
     if (len < size) {
-        virtio_error(vdev, "Cannot map desc");
+        virtio_error(vdev,
+                "Failed to map descriptor ring for device %s: "
+                "invalid guest physical address or corrupted queue setup",
+                qdev_get_printable_name(DEVICE(vdev)));
         goto err_desc;
     }
 
@@ -265,7 +268,10 @@ void virtio_init_region_cache(VirtIODevice *vdev, int n)
     len = address_space_cache_init(&new->used, vdev->dma_as,
                                    vq->vring.used, size, true);
     if (len < size) {
-        virtio_error(vdev, "Cannot map used");
+        virtio_error(vdev,
+                "Failed to map used ring for device %s: "
+                "possible guest misconfiguration or insufficient memory",
+                qdev_get_printable_name(DEVICE(vdev)));
         goto err_used;
     }
 
@@ -273,7 +279,10 @@ void virtio_init_region_cache(VirtIODevice *vdev, int n)
     len = address_space_cache_init(&new->avail, vdev->dma_as,
                                    vq->vring.avail, size, false);
     if (len < size) {
-        virtio_error(vdev, "Cannot map avail");
+        virtio_error(vdev,
+                "Failed to map avalaible ring for device %s: "
+                "possible queue misconfiguration or overlapping memory region",
+                qdev_get_printable_name(DEVICE(vdev)));
         goto err_avail;
     }