Except for the fact that with a compromised host, the virtual OS is still completely separated from the host and thus, it is independent of any malware installed in the host. The only things that could possibly affect the installed virtual OS would be a bruteforce of the keys, a very thorough but impractical analysis of the keys in SDRAM, both of which are totally useless if there's a strong key involved, i.e., a live key with a GPG-generated 512bit key.
You can never underestimate the power of:
dd if=/dev/urandom bs=512 count=4 | gpg -symmetric -a ./key.gpg
This can of course be extended and used as a failsafe; setting your [hopefully LUKS] partition to read the key from the USB, in addition to a [hopefully strong] password phrase could be considered effective.