gVisor, a security-focused container runtime, faces compatibility hurdles on Raspberry Pi 5 due to a rarely discussed kernel setting. Developers discovered that the default Raspbian OS kernel uses a 39-bit virtual address space (VA), which starves gVisor of memory for its critical shadow page tables. This issue emerged as users attempted to run sandboxed workloads on edge hardware, highlighting trade-offs between embedded system optimization and cloud-native tooling requirements.

The root cause lies in ARM64's virtual memory addressing model. While 48-bit VA configurations (256 TB address space) provide ample room for gVisor's complex memory mappings, Raspbian's 39-bit setup (512 GB) creates contention. The kernel's memory management structures consume ~60% of the available VA space, leaving insufficient headroom for gVisor's userspace kernel emulation and guest memory tracking. This manifests as cryptic "cannot allocate memory in static TLS block" errors during container initialization.

Ubuntu's ARM64 kernel, optimized for server workloads, defaults to 48-bit VA, enabling seamless gVisor operation. By modifying the kernel config to CONFIG_ARM64_VA_BITS_48=y, users can resolve the issue without hardware changes. This adjustment adds negligible overhead while unlocking full isolation benefits for edge deployments.

The runsc binary from Google's gVisor project requires no code changes to work with the updated kernel. Verification via `cat /boot/config-$(uname -r) | grep CONFIG_ARM64_VA_BITS` confirms successful configuration. This technical workaround demonstrates how low-level system settings can gatekeep modern security tools, emphasizing the need for embedded OS vendors to reconsider default kernel parameters for containerized workloads.