arm64, x86: hyperv: Report the VTL the system boots in

The hyperv guest code might run in various Virtual Trust Levels.

Report the level when the kernel boots in the non-default (0)
one.

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/20250428210742.435282-7-romank@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20250428210742.435282-7-romank@linux.microsoft.com>

Author: romank-msft

arch/arm64/hyperv/mshyperv.c

@@ -118,6 +118,8 @@ static int __init hyperv_init(void)
 	if (ms_hyperv.priv_high & HV_ACCESS_PARTITION_ID)
 		hv_get_partition_id();
 	ms_hyperv.vtl = get_vtl();
+	if (ms_hyperv.vtl > 0) /* non default VTL */
+		pr_info("Linux runs in Hyper-V Virtual Trust Level %d\n", ms_hyperv.vtl);
 
 	ms_hyperv_late_init();
 

arch/x86/hyperv/hv_vtl.c

@@ -55,7 +55,12 @@ static void  __noreturn hv_vtl_restart(char __maybe_unused *cmd)
 
 void __init hv_vtl_init_platform(void)
 {
-	pr_info("Linux runs in Hyper-V Virtual Trust Level\n");
+	/*
+	 * This function is a no-op if the VTL mode is not enabled.
+	 * If it is, this function runs if and only the kernel boots in
+	 * VTL2 which the x86 hv initialization path makes sure of.
+	 */
+	pr_info("Linux runs in Hyper-V Virtual Trust Level %d\n", ms_hyperv.vtl);
 
 	x86_platform.realmode_reserve = x86_init_noop;
 	x86_platform.realmode_init = x86_init_noop;