In the Linux kernel before 6.6.7, an untrusted VMM can trigger int80 syscall handling at any given point. This is related to arch/x86/coco/tdx/tdx.c and arch/x86/mm/mem_encrypt_amd.c.
https://ahoi-attacks.github.io/
https://cdn.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.6.7