[ovs-dev] [PATCH 2/2] netdev-dpdk: add support for vhost IOMMU feature

Kavanagh, Mark B mark.b.kavanagh at intel.com
Fri Nov 24 12:58:27 UTC 2017


>From: Kevin Traynor [mailto:ktraynor at redhat.com]
>Sent: Friday, November 24, 2017 11:31 AM
>To: Kavanagh, Mark B <mark.b.kavanagh at intel.com>; dev at openvswitch.org
>Cc: maxime.coquelin at redhat.com
>Subject: Re: [ovs-dev] [PATCH 2/2] netdev-dpdk: add support for vhost IOMMU
>feature
>
>On 11/16/2017 11:01 AM, Mark Kavanagh wrote:
>> DPDK v17.11 introduces support for the vHost IOMMU feature.
>> This is a security feature, that 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 vhost port option, vhost-iommu-support,
>> to allow enablement of the vhost IOMMU feature:
>>
>>     $ ovs-vsctl add-port br0 vhost-client-1 \
>>         -- set Interface vhost-client-1 type=dpdkvhostuserclient \
>>              options:vhost-server-path=$VHOST_USER_SOCKET_PATH   \
>>              options:vhost-iommu-support=true
>>
>> Note that support for this feature is only implemented for vhost
>> user client ports (since vhost user ports are considered deprecated).
>>
>> Signed-off-by: Mark Kavanagh <mark.b.kavanagh at intel.com>
>> Acked-by: Maxime Coquelin <maxime.coquelin at redhat.com>
>> Acked-by: Ciara Loftus <ciara.loftus at intel.com>
>> ---
>>  Documentation/topics/dpdk/vhost-user.rst | 21 +++++++++++++++++++++
>>  NEWS                                     |  1 +
>>  lib/netdev-dpdk.c                        | 29 ++++++++++++++++++++++++++---
>>  vswitchd/vswitch.xml                     | 10 ++++++++++
>>  4 files changed, 58 insertions(+), 3 deletions(-)
>>
>> diff --git a/Documentation/topics/dpdk/vhost-user.rst
>b/Documentation/topics/dpdk/vhost-user.rst
>> index 5347995..8dff901 100644
>> --- a/Documentation/topics/dpdk/vhost-user.rst
>> +++ b/Documentation/topics/dpdk/vhost-user.rst
>> @@ -250,6 +250,27 @@ Once the vhost-user-client ports have been added to the
>switch, they must be
>>  added to the guest. Like vhost-user ports, there are two ways to do this:
>using
>>  QEMU directly, or using libvirt. Only the QEMU case is covered here.
>>
>> +vhost-user client IOMMU
>> +~~~~~~~~~~~~~~~~~~~~~~~
>> +It is possible to enable IOMMU support for vHost User client ports. This 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 mode
>may
>> +be enabled on the command line::
>> +
>> +    $ ovs-vsctl add-port br0 vhost-client-1 \
>> +        -- set Interface vhost-client-1 type=dpdkvhostuserclient \
>> +             options:vhost-server-path=$VHOST_USER_SOCKET_PATH   \
>> +             options:vhost-iommu-support=true
>> +
>> +.. 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 feaure 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.
>> +
>>  Adding vhost-user-client ports to the guest (QEMU)
>>  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> diff --git a/NEWS b/NEWS
>> index 74e59bf..c15dc24 100644
>> --- a/NEWS
>> +++ b/NEWS
>> @@ -14,6 +14,7 @@ Post-v2.8.0
>>       * Add support for compiling OVS with the latest Linux 4.13 kernel
>>     - DPDK:
>>       * Add support for DPDK v17.11
>> +     * Add support for vHost IOMMU feature
>>
>>  v2.8.0 - 31 Aug 2017
>>  --------------------
>> diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
>> index ed5bf62..2e9633a 100644
>> --- a/lib/netdev-dpdk.c
>> +++ b/lib/netdev-dpdk.c
>> @@ -1424,15 +1424,29 @@ netdev_dpdk_vhost_client_set_config(struct netdev
>*netdev,
>>  {
>>      struct netdev_dpdk *dev = netdev_dpdk_cast(netdev);
>>      const char *path;
>> +    bool iommu_enable;
>> +    bool request_reconfigure = false;
>> +    uint64_t vhost_driver_flags_prev = dev->vhost_driver_flags;
>>
>>      ovs_mutex_lock(&dev->mutex);
>>      if (!(dev->vhost_driver_flags & RTE_VHOST_USER_CLIENT)) {
>>          path = smap_get(args, "vhost-server-path");
>>          if (path && strcmp(path, dev->vhost_id)) {
>>              strcpy(dev->vhost_id, path);
>> -            netdev_request_reconfigure(netdev);
>> +            request_reconfigure = true;
>>          }
>>      }
>> +
>> +    iommu_enable = smap_get_bool(args, "vhost-iommu-support", false);
>> +    if (iommu_enable)
>> +        dev->vhost_driver_flags |= RTE_VHOST_USER_IOMMU_SUPPORT;
>> +    else
>> +        dev->vhost_driver_flags &= ~RTE_VHOST_USER_IOMMU_SUPPORT;
>> +    if (vhost_driver_flags_prev != dev->vhost_driver_flags)
>> +        request_reconfigure = true;
>> +
>> +    if (request_reconfigure)
>> +        netdev_request_reconfigure(netdev);
>>      ovs_mutex_unlock(&dev->mutex);
>>
>>      return 0;
>> @@ -3326,9 +3340,18 @@ netdev_dpdk_vhost_client_reconfigure(struct netdev
>*netdev)
>>       */
>>      if (!(dev->vhost_driver_flags & RTE_VHOST_USER_CLIENT)
>>              && strlen(dev->vhost_id)) {
>> +        /* Enable vhost IOMMU, if it was requested.
>> +         * XXX: the 'flags' variable is required, as not all vhost backend
>> +         * features are currently supported by OvS; in time, it should be
>> +         * possible to invoke rte_vhost_driver_register(), passing
>> +         * dev->vhost_driver_flags directly as a parameter to same.
>> +         */
>
>Can you elaborate on this? I only see vhost_driver_flags used to
>indicate support for client and iommu, so I'm not sure the need for the
>flags variable.

Hey Kevin,

There's also RTE_VHOST_USER_DEQUEUE_ZERO_COPY, which isn't supported yet.

Thanks,
Mark

>
>> +        uint64_t flags = RTE_VHOST_USER_CLIENT;
>> +        if (dev->vhost_driver_flags & RTE_VHOST_USER_IOMMU_SUPPORT)
>> +            flags |= RTE_VHOST_USER_IOMMU_SUPPORT;
>> +
>>          /* Register client-mode device */
>> -        err = rte_vhost_driver_register(dev->vhost_id,
>> -                                        RTE_VHOST_USER_CLIENT);
>> +        err = rte_vhost_driver_register(dev->vhost_id, flags);
>>          if (err) {
>>              VLOG_ERR("vhost-user device setup failure for device %s\n",
>>                       dev->vhost_id);
>> diff --git a/vswitchd/vswitch.xml b/vswitchd/vswitch.xml
>> index c145e1a..a633226 100644
>> --- a/vswitchd/vswitch.xml
>> +++ b/vswitchd/vswitch.xml
>> @@ -2654,6 +2654,16 @@ ovs-vsctl add-port br0 p0 -- set Interface p0
>type=patch options:peer=p1 \
>>          </p>
>>        </column>
>>
>> +      <column name="options" key="vhost-iommu-support"
>> +              type='{"type": "boolean"}'>
>> +        <p>
>> +          The value specifies whether IOMMU support is enabled for a vHost
>User
>> +          client mode device that has been or will be created by QEMU.
>> +          Only supported by dpdkvhostuserclient interfaces. If not
>specified or
>> +          an incorrect value is specified, defaults to 'false'.
>> +        </p>
>> +      </column>
>> +
>>        <column name="options" key="n_rxq_desc"
>>                type='{"type": "integer", "minInteger": 1, "maxInteger":
>4096}'>
>>          <p>
>>



More information about the dev mailing list