build: Add "pmu=off" to default cpu_features option

The user sometimes doesn't care about pmu usage(e.g. perf tool profiling).
But pmu will cost significant overhead on boot time and virtualization
context switch. E.g. on arm64, if guest pmu is enabled, kvm should save
and restore all PMU registers when guest/host switching.

for dmesg comparision:
Before:
[    0.007620] bus: 'platform': driver_probe_device: matched device pmu with driver armv8-pmu
[    0.007622] bus: 'platform': really_probe: probing driver armv8-pmu with device pmu
[    0.036282] hw perfevents: enabled with armv8_pmuv3 PMU driver, 7 counters available
[    0.036285] driver: 'armv8-pmu': driver_bound: bound to device 'pmu'
[    0.036295] bus: 'platform': really_probe: bound device pmu to driver armv8-pmu

After:
[    0.007935] bus: 'platform': driver_probe_device: matched device alarmtimer with driver alarmtimer
[    0.007937] bus: 'platform': really_probe: probing driver alarmtimer with device alarmtimer
[    0.007940] driver: 'alarmtimer': driver_bound: bound to device 'alarmtimer'
[    0.007944] bus: 'platform': really_probe: bound device alarmtimer to driver alarmtimer

Because s390 doest support "pmu=off", keep the default CPUFEATURES to be ""
instead of "pmu=off".

Fixes: #2576
Signed-off-by: Jia He <[email protected]>

Makefile

@@ -398,6 +398,7 @@ USER_VARS += KERNELTYPE_ACRN
 USER_VARS += KERNELTYPE_CLH
 USER_VARS += FIRMWAREPATH
 USER_VARS += MACHINEACCELERATORS
+USER_VARS += CPUFEATURES
 USER_VARS += DEFMACHINETYPE_CLH
 USER_VARS += KERNELPARAMS
 USER_VARS += LIBEXECDIR
@@ -604,6 +605,7 @@ $(GENERATED_FILES): %: %.in $(MAKEFILE_LIST) VERSION .git-commit
 		-e "s|@INITRDPATH@|$(INITRDPATH)|g" \
 		-e "s|@FIRMWAREPATH@|$(FIRMWAREPATH)|g" \
 		-e "s|@MACHINEACCELERATORS@|$(MACHINEACCELERATORS)|g" \
+		-e "s|@CPUFEATURES@|$(CPUFEATURES)|g" \
 		-e "s|@FIRMWAREPATH_CLH@|$(FIRMWAREPATH_CLH)|g" \
 		-e "s|@DEFMACHINETYPE_CLH@|$(DEFMACHINETYPE_CLH)|g" \
 		-e "s|@KERNELPARAMS@|$(KERNELPARAMS)|g" \

arch/amd64-options.mk

@@ -8,6 +8,7 @@
 MACHINETYPE := pc
 KERNELPARAMS :=
 MACHINEACCELERATORS :=
+CPUFEATURES := pmu=off
 
 QEMUCMD := qemu-system-x86_64
 

arch/arm64-options.mk

@@ -8,6 +8,7 @@
 MACHINETYPE := virt
 KERNELPARAMS :=
 MACHINEACCELERATORS :=
+CPUFEATURES := pmu=off
 
 QEMUCMD := qemu-system-aarch64
 

arch/ppc64le-options.mk

@@ -8,5 +8,7 @@
 MACHINETYPE := pseries
 KERNELPARAMS :=
 MACHINEACCELERATORS :=
+CPUFEATURES := pmu=off
+
 KERNELTYPE := uncompressed #This architecture must use an uncompressed kernel.
 QEMUCMD := qemu-system-ppc64le

arch/s390x-options.mk

@@ -8,5 +8,6 @@
 MACHINETYPE := s390-ccw-virtio
 KERNELPARAMS :=
 MACHINEACCELERATORS :=
+CPUFEATURES :=
 
 QEMUCMD := qemu-system-s390x