smt: Do not disable SMT in virtual machines

Processors in virtual machines are *virtual*. Therefore this
only degrades the performance of the guest, but does not increase
it's security.

This patch always leaves SMT enabled in all virtual environments.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>
Signed-off-by: Arne Fitzenreiter <arne_f@ipfire.org>

src/initscripts/system/smt

@@ -20,6 +20,11 @@ case "${1}" in
 			exit 0
 		fi 2>/dev/null
 
+		# Do not disable SMT inside virtual machines
+		if [ -d "/sys/hypervisor" ]; then
+			exit 0
+		fi
+
 		# Disable SMT when the processor is vulnerable to Foreshadow or Fallout/ZombieLoad/RIDL
 		for vuln in l1tf mds; do
 			if [ -r "/sys/devices/system/cpu/vulnerabilities/${vuln}" ] && \