openvswitch/0003-netdev-dpdk-vHost-IOMMU-support.patch

From 99aa592dd03c15e9857cfc9c93cc31a8a660af7e Mon Sep 17 00:00:00 2001
From: Mark Kavanagh <mark.b.kavanagh@intel.com>
Date: Fri, 8 Dec 2017 10:53:47 +0000
Subject: [PATCH 3/3] netdev-dpdk: vHost IOMMU support

DPDK v17.11 introduces support for the vHost IOMMU feature.
This is a security feature, which restricts the vhost memory
that a virtio device may access.

This feature also enables the vhost REPLY_ACK protocol, the
implementation of which is known to work in newer versions of
QEMU (i.e. v2.10.0), but is buggy in older versions (v2.7.0 -
v2.9.0, inclusive). As such, the feature is disabled by default
in (and should remain so), for the aforementioned older QEMU
verions. Starting with QEMU v2.9.1, vhost-iommu-support can
safely be enabled, even without having an IOMMU device, with
no performance penalty.

This patch adds a new global config option, vhost-iommu-support,
that controls enablement of the vhost IOMMU feature:

    ovs-vsctl set Open_vSwitch . other_config:vhost-iommu-support=true

This value defaults to false; to enable IOMMU support, this field
should be set to true when setting other global parameters on init
(such as "dpdk-socket-mem", for example). Changing the value at
runtime is not supported, and requires restarting the vswitch daemon.

Signed-off-by: Mark Kavanagh <mark.b.kavanagh@intel.com>
Acked-by: Kevin Traynor <ktraynor@redhat.com>
Signed-off-by: Ian Stokes <ian.stokes@intel.com>
---
 Documentation/topics/dpdk/vhost-user.rst | 28 ++++++++++++++++++++++++++++
 lib/dpdk-stub.c                          |  6 ++++++
 lib/dpdk.c                               | 12 ++++++++++++
 lib/dpdk.h                               |  3 +++
 lib/netdev-dpdk.c                        | 14 ++++++++++----
 vswitchd/vswitch.xml                     | 15 +++++++++++++++
 6 files changed, 74 insertions(+), 4 deletions(-)

diff --git a/Documentation/topics/dpdk/vhost-user.rst b/Documentation/topics/dpdk/vhost-user.rst
index d383a16e3..9286f8ac6 100644
--- a/Documentation/topics/dpdk/vhost-user.rst
+++ b/Documentation/topics/dpdk/vhost-user.rst
@@ -273,6 +273,34 @@ One benefit of using this mode is the ability for vHost ports to 'reconnect' in
 event of the switch crashing or being brought down. Once it is brought back up,
 the vHost ports will reconnect automatically and normal service will resume.
 
+vhost-user-client IOMMU Support
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+vhost IOMMU is a feature which restricts the vhost memory that a virtio device
+can access, and as such is useful in deployments in which security is a
+concern.
+
+IOMMU support may be enabled via a global config value,
+```vhost-iommu-support```. Setting this to true enables vhost IOMMU support for
+all vhost ports when/where available::
+
+    $ ovs-vsctl set Open_vSwitch . other_config:vhost-iommu-support=true
+
+The default value is false.
+
+.. important::
+
+    Changing this value requires restarting the daemon.
+
+.. important::
+
+    Enabling the IOMMU feature also enables the vhost user reply-ack protocol;
+    this is known to work on QEMU v2.10.0, but is buggy on older versions
+    (2.7.0 - 2.9.0, inclusive). Consequently, the IOMMU feature is disabled by
+    default (and should remain so if using the aforementioned versions of
+    QEMU). Starting with QEMU v2.9.1, vhost-iommu-support can safely be
+    enabled, even without having an IOMMU device, with no performance penalty.
+
 .. _dpdk-testpmd:
 
 DPDK in the Guest
diff --git a/lib/dpdk-stub.c b/lib/dpdk-stub.c
index daef7291f..36021807c 100644
--- a/lib/dpdk-stub.c
+++ b/lib/dpdk-stub.c
@@ -48,3 +48,9 @@ dpdk_get_vhost_sock_dir(void)
 {
     return NULL;
 }
+
+bool
+dpdk_vhost_iommu_enabled(void)
+{
+    return false;
+}
diff --git a/lib/dpdk.c b/lib/dpdk.c
index 8da6c3244..6710d10fc 100644
--- a/lib/dpdk.c
+++ b/lib/dpdk.c
@@ -41,6 +41,7 @@ VLOG_DEFINE_THIS_MODULE(dpdk);
 static FILE *log_stream = NULL;       /* Stream for DPDK log redirection */
 
 static char *vhost_sock_dir = NULL;   /* Location of vhost-user sockets */
+static bool vhost_iommu_enabled = false; /* Status of vHost IOMMU support */
 
 static int
 process_vhost_flags(char *flag, const char *default_val, int size,
@@ -345,6 +346,11 @@ dpdk_init__(const struct smap *ovs_other_config)
         vhost_sock_dir = sock_dir_subcomponent;
     }
 
+    vhost_iommu_enabled = smap_get_bool(ovs_other_config,
+                                        "vhost-iommu-support", false);
+    VLOG_INFO("IOMMU support for vhost-user-client %s.",
+               vhost_iommu_enabled ? "enabled" : "disabled");
+
     argv = grow_argv(&argv, 0, 1);
     argc = 1;
     argv[0] = xstrdup(ovs_get_program_name());
@@ -482,6 +488,12 @@ dpdk_get_vhost_sock_dir(void)
     return vhost_sock_dir;
 }
 
+bool
+dpdk_vhost_iommu_enabled(void)
+{
+    return vhost_iommu_enabled;
+}
+
 void
 dpdk_set_lcore_id(unsigned cpu)
 {
diff --git a/lib/dpdk.h b/lib/dpdk.h
index 673a1f17e..dc58d968a 100644
--- a/lib/dpdk.h
+++ b/lib/dpdk.h
@@ -17,6 +17,8 @@
 #ifndef DPDK_H
 #define DPDK_H
 
+#include <stdbool.h>
+
 #ifdef DPDK_NETDEV
 
 #include <rte_config.h>
@@ -35,5 +37,6 @@ struct smap;
 void dpdk_init(const struct smap *ovs_other_config);
 void dpdk_set_lcore_id(unsigned cpu);
 const char *dpdk_get_vhost_sock_dir(void);
+bool dpdk_vhost_iommu_enabled(void);
 
 #endif /* dpdk.h */
diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
index b93aa2354..3082fd668 100644
--- a/lib/netdev-dpdk.c
+++ b/lib/netdev-dpdk.c
@@ -3259,6 +3259,7 @@ netdev_dpdk_vhost_client_reconfigure(struct netdev *netdev)
 {
     struct netdev_dpdk *dev = netdev_dpdk_cast(netdev);
     int err;
+    uint64_t vhost_flags = 0;
 
     ovs_mutex_lock(&dev->mutex);
 
@@ -3269,16 +3270,21 @@ netdev_dpdk_vhost_client_reconfigure(struct netdev *netdev)
      */
     if (!(dev->vhost_driver_flags & RTE_VHOST_USER_CLIENT)
             && strlen(dev->vhost_id)) {
-        /* Register client-mode device */
-        err = rte_vhost_driver_register(dev->vhost_id,
-                                        RTE_VHOST_USER_CLIENT);
+        /* Register client-mode device. */
+        vhost_flags |= RTE_VHOST_USER_CLIENT;
+
+        /* Enable IOMMU support, if explicitly requested. */
+        if (dpdk_vhost_iommu_enabled()) {
+            vhost_flags |= RTE_VHOST_USER_IOMMU_SUPPORT;
+        }
+        err = rte_vhost_driver_register(dev->vhost_id, vhost_flags);
         if (err) {
             VLOG_ERR("vhost-user device setup failure for device %s\n",
                      dev->vhost_id);
             goto unlock;
         } else {
             /* Configuration successful */
-            dev->vhost_driver_flags |= RTE_VHOST_USER_CLIENT;
+            dev->vhost_driver_flags |= vhost_flags;
             VLOG_INFO("vHost User device '%s' created in 'client' mode, "
                       "using client socket '%s'",
                       dev->up.name, dev->vhost_id);
diff --git a/vswitchd/vswitch.xml b/vswitchd/vswitch.xml
index 074535b58..8f646059f 100644
--- a/vswitchd/vswitch.xml
+++ b/vswitchd/vswitch.xml
@@ -344,6 +344,21 @@
         </p>
       </column>
 
+      <column name="other_config" key="vhost-iommu-support"
+              type='{"type": "boolean"}'>
+        <p>
+          vHost IOMMU is a security feature, which restricts the vhost memory
+          that a virtio device may access. vHost IOMMU support is disabled by
+          default, due to a bug in QEMU implementations of the vhost REPLY_ACK
+          protocol, (on which vHost IOMMU relies) prior to v2.9.1. Setting this
+          value to <code>true</code> enables vHost IOMMU support for vHost User
+          Client ports in OvS-DPDK, starting from DPDK v17.11.
+        </p>
+        <p>
+          Changing this value requires restarting the daemon.
+        </p>
+      </column>
+
       <column name="other_config" key="n-handler-threads"
               type='{"type": "integer", "minInteger": 1}'>
         <p>
-- 
2.15.1