A guest boot hangs while probing the network interface when iommu_platform=on is used.
The following qemu cli hangs without this patch: # $QEMU \ -netdev tap,fd=3,id=hostnet0,vhost=on,vhostfd=4 3<>/dev/tap67 4<>/dev/host-net \ -device virtio-net-pci,netdev=hostnet0,id=net0,iommu_platform=on,disable-legacy=on \ ... Commit: c471ad0e9bd46 (vhost_net: device IOTLB support) took care of setting vhostfd to non-blocking when QEMU opens /dev/host-net but if the fd is passed from qemu cli then we need to ensure that fd is set to non-blocking. Fixes: c471ad0e9bd46 "vhost_net: device IOTLB support" Cc: Michael S. Tsirkin <m...@redhat.com> Cc: Jason Wang <jasow...@redhat.com> Signed-off-by: Brijesh Singh <brijesh.si...@amd.com> --- net/tap.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/tap.c b/net/tap.c index 2b3a36f9b50d..8c026fbf95cd 100644 --- a/net/tap.c +++ b/net/tap.c @@ -693,6 +693,7 @@ static void net_init_tap_one(const NetdevTapOptions *tap, NetClientState *peer, } return; } + fcntl(vhostfd, F_SETFL, O_NONBLOCK); } else { vhostfd = open("/dev/vhost-net", O_RDWR); if (vhostfd < 0) { -- 2.14.3