Hi Michal,
The domain xml is attached.
Regards,
Jing Qi
On Wed, Sep 15, 2021 at 7:14 PM Michal Prívozník <mprivozn@xxxxxxxxxx> wrote:
On 9/14/21 3:05 PM, David Hildenbrand wrote:
> On 13.09.21 16:52, Michal Privoznik wrote:
>> Nothing special is happening here. All important changes were
>> done when for 'virtio-pmem' (adjusting the code to put virtio
>> memory on PCI bus, generating alias using
>> qemuDomainDeviceAliasIndex(). The only bit that might look
>> suspicious is no prealloc for virtio-mem. But if you think about
>> it, the whole purpose of this device is to change amount of
>> memory exposed to guest on the fly. There is no point in locking
>> the whole backend in memory.
>
> Do I understand correctly that we'll always try setting "reserve=off",
> and "prealloc=off"? That would be awesome :)
prealloc=off would be set (almost) unconditionally for all
memory-backend-* objects that are associated with virtio-mem device. And
if QEMU is new enough to have .reserve attribute then reserve=off is set
too.
>
> I do wonder if we want to warn or bail out if "priv->memPrealloc" is set
> but we are temporarily not able to support it -- as discussed, because
> virtio-mem in QEMU yet has to be taught about it.
priv->memPrealloc might not be what you think it is. The fact whether
immediate allocation was requested is stored in def->mem.allocation; and
priv->memPrealloc is just there to track whether -mem-prealloc what
already put onto (paritally) generated cmd line and thus the rest of
generators must refrain from setting prealloc=on.
Codewise speaking, if you'd look at qemuBuildCommandLine() (this is
where cmd line generation happens) then you'd see
qemuBuildMemCommandLine() being called first and only after that
qemuBuildMemoryDeviceCommandLine() being called second.
The former is responsible for generating generic memory for guest (e.g.
-m XX -mem-prealloc -mem-path ... which is the old style, nowadays a
combination of -machine memory-backend= + -object memory-backend-* is
generated).
Long story short, if priv->memPrealloc isn't true at this point, then
libvirt doesn't have to set prealloc=off explicitly, because off is the
default.
>
> FYI: QEMU will bail out if "reserve=off,prealloc=on" is set in combination.
Yeah, this combination should never happen.
Michal
Thanks & Regards,
Jing,Qi
Jing,Qi
<domain type='kvm' id='12'>
<name>pc</name>
<uuid>bb508b28-d57b-44bd-9e9c-a134cef24b60</uuid>
<maxMemory slots='16' unit='KiB'>8388608</maxMemory>
<memory unit='KiB'>1179648</memory>
<currentMemory unit='KiB'>1179648</currentMemory>
<memoryBacking>
<allocation mode='immediate'/>
</memoryBacking>
<vcpu placement='static'>2</vcpu>
<resource>
<partition>/machine</partition>
</resource>
<os>
<type arch='x86_64' machine='pc-i440fx-5.0'>hvm</type>
<boot dev='hd'/>
</os>
<features>
<acpi/>
<apic/>
<vmport state='off'/>
</features>
<cpu mode='custom' match='exact' check='full'>
<model fallback='forbid'>qemu64</model>
<feature policy='require' name='x2apic'/>
<feature policy='require' name='hypervisor'/>
<feature policy='require' name='lahf_lm'/>
<feature policy='disable' name='svm'/>
<numa>
<cell id='0' cpus='0-1' memory='1048576' unit='KiB' discard='yes'/>
</numa>
</cpu>
<clock offset='utc'>
<timer name='rtc' tickpolicy='catchup'/>
<timer name='pit' tickpolicy='delay'/>
<timer name='hpet' present='no'/>
</clock>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>destroy</on_crash>
<pm>
<suspend-to-mem enabled='no'/>
<suspend-to-disk enabled='no'/>
</pm>
<devices>
<emulator>/usr/bin/qemu-system-x86_64</emulator>
<disk type='file' device='disk'>
<driver name='qemu' type='qcow2'/>
<source file='/var/lib/libvirt/images/Fedora-Cloud-Base-Rawhide-20210605.n.0.x86_64.qcow2' index='1'/>
<backingStore/>
<target dev='vda' bus='virtio'/>
<alias name='virtio-disk0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x08' function='0x0'/>
</disk>
<controller type='usb' index='0' model='ich9-ehci1'>
<alias name='usb'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x7'/>
</controller>
<controller type='usb' index='0' model='ich9-uhci1'>
<alias name='usb'/>
<master startport='0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0' multifunction='on'/>
</controller>
<controller type='usb' index='0' model='ich9-uhci2'>
<alias name='usb'/>
<master startport='2'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x1'/>
</controller>
<controller type='usb' index='0' model='ich9-uhci3'>
<alias name='usb'/>
<master startport='4'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x2'/>
</controller>
<controller type='pci' index='0' model='pci-root'>
<alias name='pci.0'/>
</controller>
<controller type='ide' index='0'>
<alias name='ide'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
</controller>
<controller type='virtio-serial' index='0'>
<alias name='virtio-serial0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
</controller>
<controller type='scsi' index='0' model='virtio-scsi'>
<alias name='scsi0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x09' function='0x0'/>
</controller>
<serial type='pty'>
<source path='/dev/pts/1'/>
<target type='isa-serial' port='0'>
<model name='isa-serial'/>
</target>
<alias name='serial0'/>
</serial>
<console type='pty' tty='/dev/pts/1'>
<source path='/dev/pts/1'/>
<target type='serial' port='0'/>
<alias name='serial0'/>
</console>
<channel type='spicevmc'>
<target type='virtio' name='com.redhat.spice.0' state='disconnected'/>
<alias name='channel0'/>
<address type='virtio-serial' controller='0' bus='0' port='1'/>
</channel>
<input type='tablet' bus='usb'>
<alias name='input0'/>
<address type='usb' bus='0' port='1'/>
</input>
<input type='mouse' bus='ps2'>
<alias name='input1'/>
</input>
<input type='keyboard' bus='ps2'>
<alias name='input2'/>
</input>
<graphics type='spice' port='5900' autoport='yes' listen='127.0.0.1'>
<listen type='address' address='127.0.0.1'/>
<image compression='off'/>
</graphics>
<sound model='ich6'>
<alias name='sound0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
</sound>
<audio id='1' type='spice'/>
<video>
<model type='qxl' ram='65536' vram='65536' vgamem='16384' heads='1' primary='yes'/>
<alias name='video0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
</video>
<redirdev bus='usb' type='spicevmc'>
<alias name='redir0'/>
<address type='usb' bus='0' port='2'/>
</redirdev>
<redirdev bus='usb' type='spicevmc'>
<alias name='redir1'/>
<address type='usb' bus='0' port='3'/>
</redirdev>
<memballoon model='virtio'>
<alias name='balloon0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
</memballoon>
<memory model='virtio-mem'>
<source>
<nodemask>0</nodemask>
<pagesize unit='KiB'>2048</pagesize>
</source>
<target>
<size unit='KiB'>131072</size>
<node>0</node>
<block unit='KiB'>2048</block>
<requested unit='KiB'>131072</requested>
<current unit='KiB'>131072</current>
</target>
<alias name='virtiomem0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
</memory>
</devices>
<seclabel type='dynamic' model='selinux' relabel='yes'>
<label>system_u:system_r:svirt_t:s0:c339,c343</label>
<imagelabel>system_u:object_r:svirt_image_t:s0:c339,c343</imagelabel>
</seclabel>
<seclabel type='dynamic' model='dac' relabel='yes'>
<label>+107:+107</label>
<imagelabel>+107:+107</imagelabel>
</seclabel>
</domain>
