What happens if a Pass Through Disk/Partition changed size?

[mio19]

I used this command to attach a disk to my vm

qm set 100 -scsi7 /dev/disk/by-id/ata-HUH721010ALE601_7JHDJ6RC-part1,backup=0,replicate=0,cache=writeback,iothread=1

There is a "size" parameter visible in gui and config

scsi7: /dev/disk/by-id/ata-HUH721010ALE601_7JHDJ6RC-part1,backup=0,cache=writeback,iothread=1,replicate=0,size=8766219600K

Recently I decided to recreate part2 and I enlarged part1. Right after I powered up the vm I remembered that there is the "size" param. I killed the vm and re-attached the partition. Then I told the filesystem in vm to resize. After this everything seems working perfectly.

Why could the vm start normally with a pass through disk/partition with a mismatched size? What could potentially happen during the period?

 

[LnxBil]

Why could the vm start normally with a pass through disk/partition with a mismatched size? What could potentially happen during the period?

AFAIK, this is only relevant for the GUI, the disk size is not passed through to the QEMU/KVM process as you can see if you inspect the command line arguments to the kvm process.