From 689a30f211939282ce6de9d3597c0fc6ad674a6e Mon Sep 17 00:00:00 2001
From: Laszlo Ersek <lersek@redhat.com>
Date: Fri, 26 Jul 2019 11:29:51 +0100
Subject: [PATCH 13/14] tap: set vhostfd passed from qemu cli to non-blocking

RH-Author: Laszlo Ersek <lersek@redhat.com>
Message-id: <20190726112951.11834-2-lersek@redhat.com>
Patchwork-id: 89734
O-Subject: [RHEL-8.1.0 qemu-kvm PATCH 1/1] tap: set vhostfd passed from qemu cli to non-blocking
Bugzilla: 1732642
RH-Acked-by: Xiao Wang <jasowang@redhat.com>
RH-Acked-by: Stefano Garzarella <sgarzare@redhat.com>
RH-Acked-by: John Snow <jsnow@redhat.com>

From: Brijesh Singh <brijesh.singh@amd.com>

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: qemu-stable@nongnu.org
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
(cherry picked from commit d542800d1edc62f63f8a29cfa6bdd1a9536ae11c)
Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
---
 net/tap.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/tap.c b/net/tap.c
index 2b3a36f..89c4e19 100644
--- a/net/tap.c
+++ b/net/tap.c
@@ -40,6 +40,7 @@
 #include "qemu-common.h"
 #include "qemu/cutils.h"
 #include "qemu/error-report.h"
+#include "qemu/sockets.h"
 
 #include "net/tap.h"
 
@@ -693,6 +694,7 @@ static void net_init_tap_one(const NetdevTapOptions *tap, NetClientState *peer,
                 }
                 return;
             }
+            qemu_set_nonblock(vhostfd);
         } else {
             vhostfd = open("/dev/vhost-net", O_RDWR);
             if (vhostfd < 0) {
-- 
1.8.3.1