efi: Implement reset_system for Cloud Hypervisor - #424
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The ResetSystem runtime service was intentionally left as a no-op to force Linux to use ACPI for shutdown. However, Windows calls ResetSystem(EfiResetShutdown) as its final shutdown step and does not fall back to ACPI when the call returns. This causes the Cloud Hypervisor process to hang indefinitely after Windows shuts down. Write the appropriate value to Cloud Hypervisor's shutdown I/O port (0x600) based on the reset type: - EfiResetShutdown: SLP_TYP=5 + SLP_EN (triggers VM exit) - EfiResetCold/Warm: reboot value (triggers VM reset) The service is split into two phases because EFI applications like shim call ResetSystem during early boot when MOK state import fails (set_variable returns UNSUPPORTED). Writing to the shutdown port there made VMs either shut down on Cloud Hypervisor or hang on QEMU during boot. So reset_system_boot keeps the old no-op behavior during boot services, and the port I/O only becomes active after ExitBootServices. fixup_at_virtual remaps reset_system to its virtual address rather than not_available, so ResetSystem still works after SetVirtualAddressMap, which Windows needs to shut down on Cloud Hypervisor. Linux guests are unaffected as they use ACPI directly. Fixes: cloud-hypervisor#422 Signed-off-by: CMGS <ilskdw@gmail.com>
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Implement the EFI
ResetSystemruntime service to write to Cloud Hypervisor'sAcpiShutdownDeviceI/O port (0x600).The function was intentionally left as a no-op to force Linux to use ACPI for shutdown. Linux does fall back correctly, but Windows calls
ResetSystem(EfiResetShutdown)as its final shutdown step and does not fall back to ACPI. This causes the Cloud Hypervisor process to hang indefinitely after Windows shuts down.On x86_64, write the appropriate value based on reset type:
EfiResetShutdown: SLP_TYP=5 + SLP_EN → triggers VM exitEfiResetCold/EfiResetWarm: reboot value → triggers VM resetOn other architectures (aarch64, riscv64), the function remains a no-op — these platforms use PSCI for shutdown/reboot.
shutdown /s /t 0Linux guests are unaffected.
Fixes: #422
Signed-off-by: CMGS ilskdw@gmail.com