[ovs-dev] [PATCH 2/2] netdev-dpdk: add support for vhost IOMMU feature
Stokes, Ian
ian.stokes at intel.com
Fri Nov 24 08:18:53 UTC 2017
> Hello, Mark.
>
> Thanks for the patch. Few comments:
>
Thanks for the feedback Ilya, great minds :). The feedback is quite timely, from my point of view I'd like to see these issues resolved as quickly as possible. I don't think there's anything 'show stopper' wise in what you've raise, we should be able to correct these adjustments.
@Mark, what do you think?
Ian
> 1. We can not change the RTE_VHOST_USER_IOMMU_SUPPORT flag if device
> already
> registered, i.e. if (dev->vhost_driver_flags & RTE_VHOST_USER_CLIENT)
> != 0.
> IMHO, we should print a warning message in that case and should not
> update
> the device flags and request reconfiguration.
>
> This should be clearly described in commit message and documentation
> that
> vhost-iommu-support can't be changed if device already fully
> initialized.
> It should be clear that this option should be set before or
> simultaneously
> with vhost-server-path.
>
> 2. General style comment for the patch: According to coding style, you
> need to
> use braces for if statements even if there is only one statement in it.
>
> 3. Few more comments inline.
>
> > 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;
>
> This should be done under the mutex.
>
> >
> > 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.
>
> Above comment connected to 'if', but not the 'flags'. I'm suggesting to
> split the comment by moving above line between 'flags' declaration and the
> 'if'.
>
> > + * 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.
> > + */
> > + uint64_t flags = RTE_VHOST_USER_CLIENT
> Anyway, there should be blank line between variable declaration and the
> other code.
>
> > + 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>
> > --
> > 1.9.3
>
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