The tag backend is not supported for user/direct/hostdev network when you try to define them inside the domain XML. So, other ways to include devices cannot be permitted too. But the attach-device command is wrongly adding unsupported features. This commit fixes this bug. After the patch: virsh # attach-device rhel7.4 backend.xml error: Failed to attach device from backend.xml error: unsupported configuration: Custom tap device path is not supported for: user Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1480251 Signed-off-by: Julio Faracco <jcfaracco(a)gmail.com&gt; --- src/qemu/qemu_domain.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c index 9dab6b2..bee44d1 100644 --- a/src/qemu/qemu_domain.c +++ b/src/qemu/qemu_domain.c @@ -3622,6 +3622,16 @@ qemuDomainDeviceDefValidateNetwork(const virDomainNetDef *net) return -1; } + if (net->type == VIR_DOMAIN_NET_TYPE_DIRECT || + net->type == VIR_DOMAIN_NET_TYPE_HOSTDEV) { + if (net->backend.tap) { + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, + _("Custom tap device path is not supported for: %s"), + virDomainNetTypeToString(net->type)); + return -1; + } + } + if (STREQ_NULLABLE(net->model, "virtio")) { if (net->driver.virtio.rx_queue_size & (net->driver.virtio.rx_queue_size - 1)) { virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", -- 2.7.4