config-wsl: enable CMAC, ZSTD firmware, and MediaTek USB Bluetooth

Start with arch/x86/configs/config-wsl and compare it with the referenced diff or current linux-msft-wsl-6.18.y configuration. Confirm the three requested settings are changed as specified: built-in CMAC, ZSTD firmware compression, and MediaTek USB Bluetooth support. Done means the x86 WSL configuration contains those changes without expanding the request to firmware loading or the arm64 config.

Is your feature request related to a problem? Please describe.

Yes. Using several USB Bluetooth dongles in WSL2 (attached via usbipd) is blocked by the default WSL2 kernel config in three ways:

• MediaTek USB BT controllers have no driver. CONFIG_BT_HCIBTUSB_MTK is not set, so btusb has no MediaTek support and the controller never initializes.
• Compressed firmware can't be read. Current linux-firmware ships blobs as .zst, but CONFIG_FW_LOADER_COMPRESS_ZSTD is not set, so the direct loader can't decompress them. CONFIG_FW_LOADER_COMPRESS_XZ is enabled, but linux-firmware has moved to zstd.
• CMAC crypto fails to load on demand. CONFIG_CRYPTO_CMAC=m. BT LE Secure Connections allocates cmac(aes), which triggers a kernel-side request_module(). On WSL2 that runs through usermodehelper in the init namespace, which cannot reach the distro's /sbin/modprobe or /lib/modules, so the module never loads and the controller logs Unable to create CMAC crypto context.

Describe the solution you'd like

Three config-only changes to arch/x86/configs/config-wsl (diff: https://github.com/microsoft/WSL2-Linux-Kernel/compare/linux-msft-wsl-6.18.y...intercreate:upstream-config-cmac-zstd-mtkbt):

Describe alternatives you've considered

• CONFIG_EXTRA_FIRMWARE: must be listed per-file and stored uncompressed so it doesn't scale to arbitrary dongles.
• Carrying a downstream fork with these enabled: works as a stopgap and is what we're doing today, but the fix belongs in the shipped config so every WSL2 user benefits.

Additional context

• Diff / branch: https://github.com/microsoft/WSL2-Linux-Kernel/compare/linux-msft-wsl-6.18.y...intercreate:upstream-config-cmac-zstd-mtkbt
• Tested with Intel, Realtek (RTL8761BU), and MediaTek Bluetooth devices attached via usbipd.
• Scope: this only opens the config path. It does not fix WSL2's separate inability to load firmware from the distro's /lib/firmware while running in the init namespace.
• Same change applies to arch/arm64/configs/config-wsl-arm64 for parity if wanted; this request covers x86.