From 2c7482486c5e079d3f43cb0cc6954fe6f1f33c22 Mon Sep 17 00:00:00 2001
From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Date: Mon, 15 Aug 2016 10:40:17 +0200
Subject: [PATCH 16/17] virtio: set low features early on load
RH-Author: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-id: <1471257618-19311-2-git-send-email-dgilbert@redhat.com>
Patchwork-id: 71957
O-Subject: [RHEL-7.3 qemu-kvm-rhev PATCH 1/2] virtio: set low features early on load
Bugzilla: 1365747
RH-Acked-by: Marcel Apfelbaum <marcel@redhat.com>
RH-Acked-by: Xiao Wang <jasowang@redhat.com>
RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>
From: "Michael S. Tsirkin" <mst@redhat.com>
virtio migrates the low 32 feature bits twice, the first copy is there
for compatibility but ever since
019a3edbb25f1571e876f8af1ce4c55412939e5d: ("virtio: make features 64bit
wide") it's ignored on load. This is wrong since virtio_net_load tests
self announcement and guest offloads before the second copy including
high feature bits is loaded. This means that self announcement, control
vq and guest offloads are all broken after migration.
Fix it up by loading low feature bits: somewhat ugly since high and low
bits become out of sync temporarily, but seems unavoidable for
compatibility. The right thing to do for new features is probably to
test the host features, anyway.
Fixes: 019a3edbb25f1571e876f8af1ce4c55412939e5d
("virtio: make features 64bit wide")
Cc: qemu-stable@nongnu.org
Reported-by: Robin Geuze <robing@transip.nl>
Tested-by: Robin Geuze <robing@transip.nl>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit 62cee1a28aada2cce4b0e1fb835d8fc830aed7ac)
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
hw/virtio/virtio.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index d5933d1..300ce30 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -1511,6 +1511,16 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id)
}
qemu_get_be32s(f, &features);
+ /*
+ * Temporarily set guest_features low bits - needed by
+ * virtio net load code testing for VIRTIO_NET_F_CTRL_GUEST_OFFLOADS
+ * VIRTIO_NET_F_GUEST_ANNOUNCE and VIRTIO_NET_F_CTRL_VQ.
+ *
+ * Note: devices should always test host features in future - don't create
+ * new dependencies like this.
+ */
+ vdev->guest_features = features;
+
config_len = qemu_get_be32(f);
/*
--
1.8.3.1