Hi everyone, I have an interesting issue with DAX and KVM - I'm trying to boot a VM with its memory mapped to a DAX-mounted file (kernel 4.9).
The use case is a bit wacky but I'm trying to recreate something similar to what clearlinux[1] described (although they don't use this method anymore). When mapping the memory to a regular ext4 file, the VM boots fine. But when mapping to ext4+dax, the VM won't boot or perhaps boots extremely slowly. In both cases the FS is on a memory pmem device. Here's a snippet of how I load things: mkfs.ext4 /dev/pmem0 mount /dev/pmem0 /mnt fallocate -l 512M /mnt/mem qemu-system-x86_64 -nodefconfig -nodefaults \ -drive if=virtio,file=centos7.qcow2,index=0,media=disk \ --enable-kvm -serial telnet:localhost:4443,server,nowait \ -device sga -m 512 -smp 1,sockets=1,cores=1,threads=1 \ -object memory-backend-file,prealloc=yes,mem-path=/mnt/mem,share=on,size=512M,id=ram \ -numa node,nodeid=0,cpus=0,memdev=ram \ -net nic,model=virtio,vlan=0 \ -net user,vlan=0,hostname=vm,hostfwd=tcp:127.0.0.1:8001-:22 \ -name test -monitor telnet:localhost:4444,server,nowait I use a headless host so I usually connect to the VM with 'telnet localhost 4443'. The above works and the VM boots in seconds. When adding '-o dax' to the mount command, I can catch the grub menu during boot but it gets stuck. Sometimes if I wait about 20 minutes, I see some kernel boot messages appear, but no errors. Any thoughts? Regards, Yigal [1] https://lwn.net/Articles/644675/ _______________________________________________ Linux-nvdimm mailing list [email protected] https://lists.01.org/mailman/listinfo/linux-nvdimm
