[libvirt] [PATCH 3/3] conf: formatter/parser/RNG/docs for hostdev <driver name='kvm|vfio'/>
Eric Blake
eblake at redhat.com
Tue Apr 23 23:34:12 UTC 2013
On 04/23/2013 10:45 AM, Laine Stump wrote:
> A domain's <interface> or <hostdev>, as well as a <network>'s
> <forward>, can now have an optional <driver name='kvm|vfio'/>
> element. As of this patch, there is no functionality behind this new
> knob - this patch adds support to the domain and network
> formatter/parser, and to the RNG and documentation.
>
> When then backend is added, legacy KVM PCI device assignment will
s/then/the/
> continue to be used when no driver name is specified (or if <driver
> name='kvm'/> is specified), but if driver name is 'vfio', the new UEFI
> Secure Boot compatible VFIO device assignment will be used.
>
> Note that the parser doesn't automatically insert the current default
> value of this setting. This is done on purpose because the two
> possibilities are functionally equivalent from the guest's point of
> view, and we want to be able to automatically start using vfio as the
> default (even for existing domains) at some time in the future. This
> is similar to what was done with the "vhost" driver option in
> <interface>.
Yes, leaving an unspecified element as hypervisor default has worked for
us in the past, especially when the choice of host driver should not be
guest-visible.
> ---
> docs/formatdomain.html.in | 42 ++++++++++++++++++++++-
> docs/formatnetwork.html.in | 15 ++++++++
> docs/schemas/domaincommon.rng | 79 ++++++++++++++++++++++++++++---------------
> docs/schemas/network.rng | 11 ++++++
> src/conf/domain_conf.c | 36 ++++++++++++++++++++
> src/conf/domain_conf.h | 11 ++++++
> 6 files changed, 166 insertions(+), 28 deletions(-)
>
> diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
> index 888c005..0e5b00c 100644
> --- a/docs/formatdomain.html.in
> +++ b/docs/formatdomain.html.in
> @@ -2340,7 +2340,22 @@
> the device as can be found with the <code>lspci</code> or
> with <code>virsh
> nodedev-list</code>. <a href="#elementsAddress">See above</a> for
> - more details on the address element.
> + more details on the address element.</dd>
> + <dt><code>driver</code></dt>
> + <dd>
> + PCI devices can have an optional <code>driver</code>
> + subelement that specifies which backend driver to use for PCI
> + device assignment. Use the <code>name</code> attribute to
> + select either "vfio" (for the new VFIO device assignment
> + backend, which is compatible with UEFI SecureBoot) or "kvm"
> + (for the legacy device assignment handled directly by the KVM
> + kernel module)<span class="since">Since 1.0.5 (QEMU and KVM
> + only, requires kernel 3.6 or newer)</span>. Currently, "kvm"
> + is the default used by libvirt when not explicitly provided,
> + but since the two are functionally equivalent, this default
> + could be changed in the future with no impact to domains that
> + don't specify anything.
IIRC, we have talked about managing host devices across all hypervisors,
since it is a shared host resource. If that's true, then what happens if
LXC wants to start using a driver? Or should LXC only use vfio and
never use kvm? Also, didn't you say that xen used yet another driver,
in which case we should consider listing that in the RNG.
> + device assignment performed directly by the kvm kernel module
> + (the default is currently "kvm", but is subject to change).
> + <span class="since">Since 1.0.5 (QEMU and KVM only, requires kernel 3.6 or newer)</span>
Long line (several times).
> +++ b/docs/schemas/domaincommon.rng
> @@ -1923,28 +1923,40 @@
> </optional>
> <optional>
> <element name="driver">
> - <optional>
> - <attribute name="name">
> - <choice>
> - <value>qemu</value>
> - <value>vhost</value>
> - </choice>
> - </attribute>
> - </optional>
> - <optional>
> - <attribute name="txmode">
> - <choice>
> - <value>iothread</value>
> - <value>timer</value>
> - </choice>
> - </attribute>
> - </optional>
> - <optional>
> - <ref name="ioeventfd"/>
> - </optional>
> - <optional>
> - <ref name="event_idx"/>
> - </optional>
> + <choice>
> + <group>
> + <attribute name="name">
> + <choice>
> + <value>kvm</value>
> + <value>vfio</value>
> + </choice>
> + </attribute>
> + </group>
> + <group>
> + <optional>
> + <attribute name="name">
> + <choice>
> + <value>qemu</value>
> + <value>vhost</value>
So for define='interface-options', we are extending the exiting <driver>
so that there are now four values for <driver name=.../>, but only the
two older options allow other attributes.
Can the two ever overlap, or are we safe in that kvm/vfio are for
hostdev interface passthrough, while qemu/vhost is for emulation, so the
two types of driver choices never make sense at once?
> + </choice>
> + </attribute>
> + </optional>
> + <optional>
> + <attribute name="txmode">
> + <choice>
> + <value>iothread</value>
> + <value>timer</value>
> + </choice>
> + </attribute>
> + </optional>
> + <optional>
> + <ref name="ioeventfd"/>
> + </optional>
> + <optional>
> + <ref name="event_idx"/>
> + </optional>
> + </group>
> + </choice>
> <empty/>
> </element>
> </optional>
> @@ -3084,14 +3096,27 @@
> <attribute name="type">
> <value>pci</value>
> </attribute>
> - <element name="source">
> + <interleave>
> <optional>
> - <ref name="startupPolicy"/>
> + <element name="driver">
> + <attribute name="name">
> + <choice>
> + <value>kvm</value>
> + <value>vfio</value>
> + </choice>
> + </attribute>
> + <empty/>
Whereas for define='hostdevsubsyspci', we are completely adding a new
subelement, with only two choices for the new attribute.
> + </element>
> </optional>
> - <element name="address">
> - <ref name="pciaddress"/>
> + <element name="source">
> + <optional>
> + <ref name="startupPolicy"/>
> + </optional>
> + <element name="address">
> + <ref name="pciaddress"/>
> + </element>
> </element>
> - </element>
> + </interleave>
> </define>
>
> <define name="hostdevsubsysusb">
> diff --git a/docs/schemas/network.rng b/docs/schemas/network.rng
> index 6c3fae2..493edae 100644
> --- a/docs/schemas/network.rng
> +++ b/docs/schemas/network.rng
> @@ -149,6 +149,17 @@
> </attribute>
> </element>
> </optional>
> + <optional>
> + <element name="driver">
> + <attribute name="name">
> + <choice>
> + <value>kvm</value>
> + <value>vfio</value>
> + </choice>
> + </attribute>
> + <empty/>
> + </element>
> + </optional>
> </interleave>
Looks okay to me.
I'm not sure if we are ready to push this without more patches in the
series, but at least I think the XML is on the right track.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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