An issue was discovered in the Linux kernel before 5.9. arch/x86/kvm/svm/sev.c allows attackers to cause a denial of service (soft lockup) by triggering destruction of a large SEV VM (which requires unregistering many encrypted regions), aka CID-7be74942f184.
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.9
https://lists.debian.org/debian-lts-announce/2021/07/msg00015.html