<div dir="ltr">I did some test for virtio-mem with libvirt upstream version v7.0.0-153-g5ea3ecd07d & qemu-kvm-5.2.0-0.7.rc2.fc34.x86_64 S1. Start domain with memory device 1. Domain configuration- <maxMemory slots='16' unit='KiB'>10485760</maxMemory> <memory unit='KiB'>1572864</memory> <currentMemory unit='KiB'>1572864</currentMemory> ... <cpu mode='host-model' check='partial'> <numa> <cell id='0' cpus='0-3' memory='1048576' unit='KiB'/> </numa> </cpu> ... <memory model='virtio-mem'> <target> <size unit='KiB'>524288</size> <node>0</node> <block unit='KiB'>2048</block> <requested unit='KiB'>393216</requested> </target> <address type='pci' domain='0x0000' bus='0x00' slot='0x0a' function='0x0'/> </memory> #virsh start pc<div> Domain 'pc' started 2. The domain is started and check mem status, the actual size is "1048576" #virsh dommemstat pc actual 1048576 swap_in 0 swap_out 0 major_fault 257 minor_fault 130540 unused 604064 available 761328 usable 578428 last_update 1612325471 disk_caches 49632 hugetlb_pgalloc 0 hugetlb_pgfail 0 rss 460260 3. Then, check the active xml - # virsh dumpxml pc ... <memory unit='KiB'>1572864</memory> <currentMemory unit='KiB'>1048576</currentMemory> .... <memory model='virtio-mem'> <target> <size unit='KiB'>524288</size> <node>0</node> <block unit='KiB'>2048</block> <requested unit='KiB'>393216</requested> <actual unit='KiB'>0</actual> </target> <alias name='virtiomem0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x0a' function='0x0'/> </memory> Question1 : the value of actual is "0". Is it expected? S2. Also, tried to use hugepage to start the domain - <memory model='virtio-mem'> <target> <size unit='KiB'>524288</size> <node>0</node> <block unit='KiB'>2048</block> <requested unit='KiB'>393216</requested> <actual unit='KiB'>0</actual> </target> <alias name='virtiomem0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x0a' function='0x0'/> </memory> #virsh start pc error: Failed to start domain 'pc' error: internal error: process exited while connecting to monitor: 2021-02-03T05:50:33.157836Z qemu-system-x86_64: -object memory-backend-file,id=memvirtiomem0,mem-path=/dev/hugepages/libvirt/qemu/9-pc,size=536870912,host-nodes=0,policy=bind: can't open backing store /dev/hugepages/libvirt/qemu/9-pc for guest RAM: Permission denied </div><div> </div><div>Question 2: any bug here?</div></div> <div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Feb 2, 2021 at 9:44 PM Peter Krempa <<a href="mailto:pkrempa@redhat.com">pkrempa@redhat.com</a>> wrote: </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">On Fri, Jan 22, 2021 at 13:50:21 +0100, Michal Privoznik wrote: > Technically, this is another version of: > > <a href="https://www.redhat.com/archives/libvir-list/2020-December/msg00199.html" rel="noreferrer" target="_blank">https://www.redhat.com/archives/libvir-list/2020-December/msg00199.html</a> > > But since virtio-pmem part is pushed now, I've reworked virtio-mem a bit > and sending it as a new series. > > For curious ones, David summarized behaviour well when implementing > virtio-mem support in kernel: > > <a href="https://lwn.net/Articles/755423/" rel="noreferrer" target="_blank">https://lwn.net/Articles/755423/</a> > > For less curious ones: > > # virsh update-memory $dom --requested-size 4G > > adds additional 4GiB of RAM to guest; > > # virsh update-memory $dom --requested-size 0 > > removes those 4GiB added earlier. > > Patches are also available on my GitLab: > > <a href="https://gitlab.com/MichalPrivoznik/libvirt/-/tree/virtio_mem_v3" rel="noreferrer" target="_blank">https://gitlab.com/MichalPrivoznik/libvirt/-/tree/virtio_mem_v3</a> > Patches 1-7,9-10 (but observe some individual comments, including the rename of the virsh commands): Reviewed-by: Peter Krempa <<a href="mailto:pkrempa@redhat.com" target="_blank">pkrempa@redhat.com</a>> Patch 8 has severe semantic problems. </blockquote></div> <div> </div>-- <div dir="ltr" class="gmail_signature"><div dir="ltr">Thanks & Regards, Jing,Qi </div></div>