linux-kernel - [PATCH hyperv-next v6 06/11] arm64, x86: hyperv: Report the VTL the system boots in

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Message-ID: <20250315001931.631210-7-romank@linux.microsoft.com>
Date: Fri, 14 Mar 2025 17:19:26 -0700
From: Roman Kisel <romank@...ux.microsoft.com>
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Subject: [PATCH hyperv-next v6 06/11] 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@...ux.microsoft.com>
---
 arch/arm64/hyperv/mshyperv.c | 2 ++
 arch/x86/hyperv/hv_vtl.c     | 7 ++++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c
index f251a08ada5b..ecbd2f5c955e 100644
--- a/arch/arm64/hyperv/mshyperv.c
+++ b/arch/arm64/hyperv/mshyperv.c
@@ -110,6 +110,8 @@ 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();
 
diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
index 582fe820e29c..038c896fdd60 100644
--- a/arch/x86/hyperv/hv_vtl.c
+++ b/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;
-- 
2.43.0