x86/hyperv: Add VTL mode callback for restarting the system

The kernel runs as a firmware in the VTL mode, and the only way
to restart in the VTL mode on x86 is to triple fault. Thus, one
has to always supply "reboot=t" on the kernel command line in the
VTL mode, and missing that renders rebooting not working.

Define the machine restart callback to always use the triple
fault to provide the robust configuration by default.

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Link: https://lore.kernel.org/r/20250227214728.15672-3-romank@linux.microsoft.com


Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20250227214728.15672-3-romank@linux.microsoft.com>