libvirt/tests/qemuxml2argvdata/memory-hotplug-nvdimm-pmem.x86_64-latest.args
Michal Privoznik bf14a9be1e qemu: Don't prealloc mem for real NVDIMMs
Currently, we configure QEMU to prealloc memory almost by
default. Well, by default for NVDIMMs, hugepages and if user
asked us to (via memoryBacking <allocation mode="immediate"/>).

However, when guest's NVDIMM is backed by real life NVDIMM this
approach is not the best. In this case users should put <pmem/>
into the <memory/> device <source/>, like this:

  <memory model='nvdimm' access='shared'>
    <source>
      <path>/dev/pmem0</path>
      <pmem/>
    </source>
  </memory>

Instructing QEMU to do prealloc in this case means that each
page of the NVDIMM is "touched" (the first byte is read and
written back - see QEMU commit v2.9.0-rc1~26^2) which cripples
device wear.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1894053
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
2021-01-05 13:19:22 +01:00

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LC_ALL=C \
PATH=/bin \
HOME=/tmp/lib/domain--1-QEMUGuest1 \
USER=test \
LOGNAME=test \
XDG_DATA_HOME=/tmp/lib/domain--1-QEMUGuest1/.local/share \
XDG_CACHE_HOME=/tmp/lib/domain--1-QEMUGuest1/.cache \
XDG_CONFIG_HOME=/tmp/lib/domain--1-QEMUGuest1/.config \
QEMU_AUDIO_DRV=none \
/usr/bin/qemu-system-i386 \
-name guest=QEMUGuest1,debug-threads=on \
-S \
-object secret,id=masterKey0,format=raw,\
file=/tmp/lib/domain--1-QEMUGuest1/master-key.aes \
-machine pc,accel=tcg,usb=off,dump-guest-core=off,nvdimm=on \
-cpu qemu64 \
-m size=219136k,slots=16,maxmem=1099511627776k \
-overcommit mem-lock=off \
-smp 2,sockets=2,dies=1,cores=1,threads=1 \
-object memory-backend-ram,id=ram-node0,size=224395264 \
-numa node,nodeid=0,cpus=0-1,memdev=ram-node0 \
-object memory-backend-file,id=memnvdimm0,mem-path=/tmp/nvdimm,share=no,\
size=536870912,pmem=yes \
-device nvdimm,node=0,memdev=memnvdimm0,id=nvdimm0,slot=0 \
-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
-display none \
-no-user-config \
-nodefaults \
-chardev socket,id=charmonitor,fd=1729,server,nowait \
-mon chardev=charmonitor,id=monitor,mode=control \
-rtc base=utc \
-no-shutdown \
-no-acpi \
-boot strict=on \
-device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 \
-blockdev '{"driver":"host_device","filename":"/dev/HostVG/QEMUGuest1",\
"node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap"}' \
-blockdev '{"node-name":"libvirt-1-format","read-only":false,"driver":"raw",\
"file":"libvirt-1-storage"}' \
-device ide-hd,bus=ide.0,unit=0,drive=libvirt-1-format,id=ide0-0-0,bootindex=1 \
-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3 \
-sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,\
resourcecontrol=deny \
-msg timestamp=on