VM blocked on humongus amounts of disk read

[os19000]

Problem occurring since updating to 6.1.36 from 6.1.34

running condition tested for reproduction:

• on a old windows 10 host install, run old or new Linux guests (both EFI, and non EFI) that were working on 6.1.34
• on a fresh windows 10 host install (21H2), with the same scenarios.

steps to reproduce:

• from a system without VirtualBox installed, or with VirtualBox 6.1.34 installed:
  • install or update to 6.1.36,
  • try to run any linux guest

observed behavior:

• at startup a 19GB vdi guest generates a 100 second read @ 600+ MB/s (so about 60GB read) blocking the guest execution for the whole time,
• after logging in, a second wave of read is triggered (about 30s, so 20GB),
• and on shutdown the read is also triggered for about 90 seconds rendering the whole process very cumbersome and sluggish.
• note: using the menu to insert guest additions CD also triggers a read freeze.

[os19000]

machine log

[os19000]

problem solved itself after this morning's windows update.