Re: [Libguestfs] virt-p2v VM testing bitrot?

On Wed, Aug 24, 2022 at 05:25:50PM +0200, Laszlo Ersek wrote: > On 08/24/22 16:13, Richard W.M. Jones wrote: >> On Wed, Aug 24, 2022 at 04:12:04PM +0200, Laszlo Ersek wrote: >>> I've started looking into RHBZ 1590721 for virt-p2v. >>> >>> For p2v development, quick local testing is helpful. "make >>> run-virt-p2v-directly" seems to be working great; however, the VM-based >>> test methods seem to have developed problems, since I last looked. >>> >>> Namely: >>> >>> - "make run-virt-p2v-in-a-vm" boots quickly, but the GUI does not come up. >>> >>> - "make run-virt-p2v-in-an-nvme-vm" boots *incredibly slowly*. I >>> checked, and the host CPU utilization during guest boot was around 20% >>> (and KVM was enabled). I don't understand how or why, but exposing the >>> "physical machine" disk over NVMe slows guest boot to a crawl -- it >>> looks strangely "IO-bound". I don't recall this from the time I added >>> this Makefile target! >>> >>> Do these symptoms look familiar? >> >> Yes I had noticed this. I did look at it briefly but couldn't work >> out what was going wrong. > > Thanks for confirming! > > I think I've found something, at least in relation to the first issue > (i.e., run-virt-p2v-in-a-vm booting quickly, but not launching the p2v > service). The problem seems to be the following: > > - Both the "physical machine" disk (fedora.img) and the bootable p2v > disk (virt-p2v.img) are based on Fedora 35. The former because of commit > 3b59d4acb82f ("Use fedora-35 as the test physical machine", 2022-05-10), > the latter because my host system runs Fedora 35, and so > virt-p2v-make-disk picks F35. > > - Consequently, both the "hd0" drive and the "usb0" drive are based on > the same Fedora 35 virt-builder template. > > - The grub command line (part of *both* images) specifies the *same* > kernel parameter "root=UUID=fae2...". > > - This filesystem UUID exists *twice* in the virtual machine however, > once in "hd0" and another time in "usb0" -- duplicate UUID. > > - The guest kernel ends up mounting / loading the root filesystem from > "hd0", that is, the "physical machine" Fedora 35 image, which does not > have anything injected that's related to p2v. Ah yes, I remember being extremely confused by why it was booting the wrong guest, and also I remember this exact bug having happened long ago in the past. Can we re-randomize the file system UUID of one of them when creating the test disks?