A lot of people copy libvirt's command line from ps -ef and then wonder why the VM isn't working correctly. Let's be kind and tell them what they should do instead.
Without this patch, if you run with an invalid -net tap,fd=X, the guest still runs and we poll 100% on a bad file descriptor. With this patch, you get: qemu: -net tap,fd=42: invalid fd= for tap network device. If you're copying from libvirt, use `virsh dom2xml-to-native' instead qemu: -net tap,fd=42: Device 'tap' could not be initialized Signed-off-by: Anthony Liguori <aligu...@us.ibm.com> --- v1 -> v2 - Remove garbage from unclean commit (spotted by Alex Graf) diff --git a/net/tap.c b/net/tap.c index 0147dab..45b1fb6 100644 --- a/net/tap.c +++ b/net/tap.c @@ -405,6 +405,8 @@ int net_init_tap(QemuOpts *opts, Monitor *mon, const char *name, VLANState *vlan int fd, vnet_hdr = 0; if (qemu_opt_get(opts, "fd")) { + int flags; + if (qemu_opt_get(opts, "ifname") || qemu_opt_get(opts, "script") || qemu_opt_get(opts, "downscript") || @@ -418,6 +420,11 @@ int net_init_tap(QemuOpts *opts, Monitor *mon, const char *name, VLANState *vlan return -1; } + if (fcntl(fd, F_GETFL, &flags) == -1) { + error_report("invalid fd= for tap network device. If you're copying from libvirt, use `virsh dom2xml-to-native' instead"); + return -1; + } + fcntl(fd, F_SETFL, O_NONBLOCK); vnet_hdr = tap_probe_vnet_hdr(fd); -- 1.7.0.4