From fec618a3fdcc88fa50089edb5748a6554ac49070 Mon Sep 17 00:00:00 2001
From: Maxime Coquelin <maxime.coquelin@redhat.com>
Date: Wed, 13 Dec 2017 09:51:06 +0100
Subject: [PATCH 1/6] vhost: prevent features to be changed while device is
 running

As section 2.2 of the Virtio spec states about features
negotiation:
"During device initialization, the driver reads this and tells
the device the subset that it accepts. The only way to
renegotiate is to reset the device."

This patch implements a check to prevent illegal features change
while the device is running.

One exception is the VHOST_F_LOG_ALL feature bit, which is enabled
when live-migration is initiated. But this feature is not negotiated
with the Virtio driver, but directly with the Vhost master.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Acked-by: Yuanhan Liu <yliu@fridaylinux.org>
(cherry picked from commit 07f8db29b8833378dd506f3e197319f8b669aed9)
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 dpdk-17.11/lib/librte_vhost/vhost_user.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/dpdk-17.11/lib/librte_vhost/vhost_user.c b/dpdk-17.11/lib/librte_vhost/vhost_user.c
index f4c7ce462..545dbcb2b 100644
--- a/dpdk-17.11/lib/librte_vhost/vhost_user.c
+++ b/dpdk-17.11/lib/librte_vhost/vhost_user.c
@@ -183,7 +183,22 @@ vhost_user_set_features(struct virtio_net *dev, uint64_t features)
 		return -1;
 	}
 
-	if ((dev->flags & VIRTIO_DEV_RUNNING) && dev->features != features) {
+	if (dev->flags & VIRTIO_DEV_RUNNING) {
+		if (dev->features == features)
+			return 0;
+
+		/*
+		 * Error out if master tries to change features while device is
+		 * in running state. The exception being VHOST_F_LOG_ALL, which
+		 * is enabled when the live-migration starts.
+		 */
+		if ((dev->features ^ features) & ~(1ULL << VHOST_F_LOG_ALL)) {
+			RTE_LOG(ERR, VHOST_CONFIG,
+				"(%d) features changed while device is running.\n",
+				dev->vid);
+			return -1;
+		}
+
 		if (dev->notify_ops->features_changed)
 			dev->notify_ops->features_changed(dev->vid, features);
 	}
-- 
2.14.3

