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@xxxxxxxxxx>
---
docs/formatdomain.html.in | 57 +++++++++++++++++++++++--
docs/schemas/domaincommon.rng | 32 ++++++++++++++
tests/qemuxml2argvdata/disk-nvme.xml | 63 ++++++++++++++++++++++++++++
3 files changed, 149 insertions(+), 3 deletions(-)
create mode 100644 tests/qemuxml2argvdata/disk-nvme.xml
diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
index 93991aa3d1..ad116ff509 100644
--- a/docs/formatdomain.html.in
+++ b/docs/formatdomain.html.in
@@ -2934,6 +2934,13 @@
</backingStore>
<target dev='vdd' bus='virtio'/>
</disk>
+ <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='vde' bus='virtio'/>
+ </disk>
</devices>
...</pre>
@@ -2947,7 +2954,8 @@
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 5.6.0</span>)
and refer to the underlying source for the disk.
<span class="since">Since 0.0.3</span>
</dd>
@@ -3130,6 +3138,43 @@
<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><disk type='nvme'></code>
+ and <code><hostdev/></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><disk type='block'></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
@@ -3292,11 +3337,17 @@
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 5.6.0</span>
+ </dd>
</dl>
<p>
- For a "file" or "volume" disk type which represents a cdrom or floppy
- (the <code>device</code> attribute), it is possible to define
+ For a "file" or "volume" disk type which represents a cdrom or
+ floppy (the <code>device</code> attribute), it is possible to define
policy what to do with the disk if the source file is not accessible.
(NB, <code>startupPolicy</code> is not valid for "volume" disk unless
the specified storage volume is of "file" type). This is done by the
diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
index 40eb4a2d75..4871a4c4d4 100644
--- a/docs/schemas/domaincommon.rng
+++ b/docs/schemas/domaincommon.rng
@@ -1603,6 +1603,7 @@
<ref name="diskSourceDir"/>
<ref name="diskSourceNetwork"/>
<ref name="diskSourceVolume"/>
+ <ref name="diskSourceNvme"/>
</choice>
</define>
@@ -1918,6 +1919,37 @@
</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>
diff --git a/tests/qemuxml2argvdata/disk-nvme.xml b/tests/qemuxml2argvdata/disk-nvme.xml
new file mode 100644
index 0000000000..66b2d8450e
--- /dev/null
+++ b/tests/qemuxml2argvdata/disk-nvme.xml
@@ -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-i686</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>
--
2.21.0
--
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