13.0-CURRENT: Cannot probe medium sector size

[Trond Endrestøl]

I have a non-vital VM on XenServer 7.6, running:

FreeBSD freebsd-head-zfs.FQDN 13.0-CURRENT FreeBSD 13.0-CURRENT #0 r340244: Thu Nov  8 12:47:24 CET 2018     root at freebsd-head-zfs.FQDN:/usr/obj/usr/src/amd64.amd64/sys/XENGUEST  amd64 1300003 1300003

The boot disks are partitioned as shown below:

$ gpart show -p ada0 ada1 ada2
=>      40  33554352    ada0  GPT  (16G)
        40      1024  ada0p1  freebsd-boot  (512K)
      1064  33553320  ada0p2  freebsd-zfs  (16G)
  33554384         8          - free -  (4.0K)

=>      40  33554352    ada1  GPT  (16G)
        40      1024  ada1p1  freebsd-boot  (512K)
      1064  33553320  ada1p2  freebsd-zfs  (16G)
  33554384         8          - free -  (4.0K)

=>      40  33554352    ada2  GPT  (16G)
        40      1024  ada2p1  freebsd-boot  (512K)
      1064  33553320  ada2p2  freebsd-zfs  (16G)
  33554384         8          - free -  (4.0K)

Before and while presenting the boot loader's menu, the screen is 
filled with:

Cannot probe medium sector size

See https://ximalas.info/~trond/13.0-CURRENT-r340244-Cannot-probe-medium-sector-size/13.0-CURRENT-r340244-Cannot-probe-medium-sector-size.png

The system is bootable. It's been like this for a long time, but I 
figured it's time to do something, if possible.

Are there any chance of silencing these messages?
Are the partitions misaligned?
Does XenServer convey the necessary information?

The same issue holds true for non-UEFI systems running under recent 
versions of VirtualBox. (XenServer supports only BIOS/legacy boot firmware.)

-- 
Trond.