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schemas: Introduce disk type NVMe

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There is this class of PCI devices that act like disks: NVMe.
Therefore, they are both PCI devices and disks. While we already
have <hostdev/> (and can assign a NVMe device to a domain
successfully) we don't have disk representation. There are three
problems with PCI assignment in case of a NVMe device:

1) domains with <hostdev/> can't be migrated

2) NVMe device is assigned whole, there's no way to assign only a
   namespace

3) Because hypervisors see <hostdev/> they don't put block layer
   on top of it - users don't get all the fancy features like
   snapshots

NVMe namespaces are way of splitting one continuous NVDIMM memory
into smaller ones, effectively creating smaller NVMe-s (which can
then be partitioned, LVMed, etc.)

Because of all of this the following XML was chosen to model a
NVMe device:

  <disk type='nvme' device='disk'>
    <driver name='qemu' type='raw'/>
    <source type='pci' managed='yes' namespace='1'>
      <address domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
    </source>
    <target dev='vda' bus='virtio'/>
  </disk>

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Cole Robinson <crobinso@redhat.com>
This commit is contained in:
Michal Privoznik 2019-06-03 10:46:18 +02:00
parent 1ee471960b
commit e1b022890e
3 changed files with 147 additions and 1 deletions
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53
docs/formatdomain.html.in
View File

@ -2948,6 +2948,13 @@
&lt;/backingStore&gt;
&lt;target dev='vdd' bus='virtio'/&gt;
&lt;/disk&gt;
&lt;disk type='nvme' device='disk'&gt;
&lt;driver name='qemu' type='raw'/&gt;
&lt;source type='pci' managed='yes' namespace='1'&gt;
&lt;address domain='0x0000' bus='0x01' slot='0x00' function='0x0'/&gt;
&lt;/source&gt;
&lt;target dev='vde' bus='virtio'/&gt;
&lt;/disk&gt;
&lt;/devices&gt;
...</pre>
@ -2961,7 +2968,8 @@
Valid values are "file", "block",
"dir" (<span class="since">since 0.7.5</span>),
"network" (<span class="since">since 0.8.7</span>), or
"volume" (<span class="since">since 1.0.5</span>)
"volume" (<span class="since">since 1.0.5</span>), or
"nvme" (<span class="since">since 6.0.0</span>)
and refer to the underlying source for the disk.
<span class="since">Since 0.0.3</span>
</dd>
@ -3144,6 +3152,43 @@
<span class="since">Since 1.0.5</span>
</p>
</dd>
<dt><code>nvme</code></dt>
<dd>
To specify disk source for NVMe disk the <code>source</code>
element has the following attributes:
<dl>
<dt><code>type</code></dt>
<dd>The type of address specified in <code>address</code>
sub-element. Currently, only <code>pci</code> value is
accepted.
</dd>
<dt><code>managed</code></dt>
<dd>This attribute instructs libvirt to detach NVMe
controller automatically on domain startup (<code>yes</code>)
or expect the controller to be detached by system
administrator (<code>no</code>).
</dd>
<dt><code>namespace</code></dt>
<dd>The namespace ID which should be assigned to the domain.
According to NVMe standard, namespace numbers start from 1,
including.
</dd>
</dl>
The difference between <code>&lt;disk type='nvme'&gt;</code>
and <code>&lt;hostdev/&gt;</code> is that the latter is plain
host device assignment with all its limitations (e.g. no live
migration), while the former makes hypervisor to run the NVMe
disk through hypervisor's block layer thus enabling all
features provided by the layer (e.g. snapshots, domain
migration, etc.). Moreover, since the NVMe disk is unbinded
from its PCI driver, the host kernel storage stack is not
involved (compared to passing say <code>/dev/nvme0n1</code> via
<code>&lt;disk type='block'&gt;</code> and therefore lower
latencies can be achieved.
</dd>
</dl>
With "file", "block", and "volume", one or more optional
sub-elements <code>seclabel</code>, <a href="#seclabel">described
@ -3306,6 +3351,12 @@
initiator IQN needed to access the source via mandatory
attribute <code>name</code>.
</dd>
<dt><code>address</code></dt>
<dd>For disk of type <code>nvme</code> this element
specifies the PCI address of the host NVMe
controller.
<span class="since">Since 6.0.0</span>
</dd>
</dl>
<p>

32
docs/schemas/domaincommon.rng
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@ -1610,6 +1610,7 @@
<ref name="diskSourceDir"/>
<ref name="diskSourceNetwork"/>
<ref name="diskSourceVolume"/>
<ref name="diskSourceNvme"/>
</choice>
</define>
@ -1925,6 +1926,37 @@
</optional>
</define>
<define name="diskSourceNvme">
<attribute name="type">
<value>nvme</value>
</attribute>
<optional>
<element name="source">
<attribute name="type">
<value>pci</value>
</attribute>
<attribute name="namespace">
<ref name="uint32"/>
</attribute>
<optional>
<attribute name="managed">
<ref name="virYesNo"/>
</attribute>
</optional>
<element name="address">
<ref name="pciaddress"/>
</element>
<ref name="diskSourceCommon"/>
<optional>
<ref name="storageStartupPolicy"/>
</optional>
<optional>
<ref name="encryption"/>
</optional>
</element>
</optional>
</define>
<define name="diskTarget">
<data type="string">
<param name="pattern">(ioemu:)?(fd|hd|sd|vd|xvd|ubd)[a-zA-Z0-9_]+</param>

63
tests/qemuxml2argvdata/disk-nvme.xml Normal file
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@ -0,0 +1,63 @@
<domain type='qemu'>
<name>QEMUGuest1</name>
<uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
<memory unit='KiB'>219136</memory>
<currentMemory unit='KiB'>219136</currentMemory>
<vcpu placement='static'>1</vcpu>
<os>
<type arch='i686' machine='pc'>hvm</type>
<boot dev='hd'/>
</os>
<clock offset='utc'/>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>destroy</on_crash>
<devices>
<emulator>/usr/bin/qemu-system-i386</emulator>
<disk type='nvme' device='disk'>
<driver name='qemu' type='raw'/>
<source type='pci' managed='yes' namespace='1'>
<address domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
</source>
<target dev='vda' bus='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
</disk>
<disk type='nvme' device='disk'>
<driver name='qemu' type='raw'/>
<source type='pci' managed='yes' namespace='2'>
<address domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
</source>
<target dev='vdb' bus='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
</disk>
<disk type='nvme' device='disk'>
<driver name='qemu' type='raw'/>
<source type='pci' managed='no' namespace='1'>
<address domain='0x0000' bus='0x02' slot='0x00' function='0x0'/>
</source>
<target dev='vdc' bus='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
</disk>
<disk type='nvme' device='disk'>
<driver name='qemu' type='qcow2' cache='none'/>
<source type='pci' managed='no' namespace='2'>
<address domain='0x0001' bus='0x02' slot='0x00' function='0x0'/>
<encryption format='luks'>
<secret type='passphrase' uuid='0a81f5b2-8403-7b23-c8d6-21ccc2f80d6f'/>
</encryption>
</source>
<target dev='vdd' bus='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
</disk>
<controller type='usb' index='0'>
<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
</controller>
<controller type='pci' index='0' model='pci-root'/>
<controller type='scsi' index='0' model='virtio-scsi'>
<address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
</controller>
<input type='mouse' bus='ps2'/>
<input type='keyboard' bus='ps2'/>
<memballoon model='none'/>
</devices>
</domain>