From 5e6f9314331c0abedecd54f1a21806bcc9daafe1 Mon Sep 17 00:00:00 2001
From: Kroese <kroese@users.noreply.github.com>
Date: Fri, 14 Mar 2025 14:16:10 +0100
Subject: [PATCH] feat: Detect clock source (#923)

---
 src/proc.sh | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/src/proc.sh b/src/proc.sh
index 34d8013..56b2466 100644
--- a/src/proc.sh
+++ b/src/proc.sh
@@ -9,6 +9,23 @@ set -Eeuo pipefail
 : "${CPU_MODEL:=""}"
 : "${DEF_MODEL:="qemu64"}"
 
+CLOCKSOURCE="tsc"
+[[ "${ARCH,,}" == "arm64" ]] && CLOCKSOURCE="arch_sys_counter"
+CLOCK="/sys/devices/system/clocksource/clocksource0/current_clocksource"
+
+if [ ! -f "$CLOCK" ]; then
+  warn "file \"$CLOCK\" cannot not found?"
+else
+  result=$(<"$CLOCK")
+  case "${result,,}" in
+    "${CLOCKSOURCE,,}" ) ;;
+    "kvm-clock" ) info "Nested KVM virtualization detected.." ;;
+    "hyperv_clocksource_tsc_page" ) info "Nested Hyper-V virtualization detected.." ;;
+    "hpet" ) warn "unsupported clock source detected: '$result'. Please set host clock source to '$CLOCKSOURCE'" ;;
+    *) warn "unexpected clock source detected: '$result'. Please set host clock source to '$CLOCKSOURCE'" ;;
+  esac
+fi
+
 if [[ "${ARCH,,}" != "amd64" ]]; then
   KVM="N"
   warn "your CPU architecture is ${ARCH^^} and cannot provide KVM acceleration for x64 instructions, this will cause a major loss of performance."
@@ -60,16 +77,6 @@ if [[ "$KVM" != [Nn]* ]]; then
     CPU_FEATURES+=",migratable=no"
   fi
 
-  CLOCK="/sys/devices/system/clocksource/clocksource0/current_clocksource"
-  if [ -f "$CLOCK" ]; then
-    result=$(<"$CLOCK")
-    if [[ "${result,,}" != "tsc" ]]; then
-      warn "unexpected clocksource: $result"
-    fi
-  else
-    warn "file \"$CLOCK\" cannot not found?"
-  fi
-
   if grep -qw "svm" <<< "$flags"; then
 
     # AMD processor