Make it easy to change the number of CPUs

diff --git a/Makefile b/Makefile
index 37924e228c78ca4012807d1adb0929942276697b..30cec7c4444f4cddb462c7081b93f048b541b695 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -179,7 +179,10 @@ GDBPORT = $(shell expr `id -u` % 5000 + 25000)
 QEMUGDB = $(shell if $(QEMU) -help | grep -q '^-gdb'; \
        then echo "-gdb tcp::$(GDBPORT)"; \
        else echo "-s -p $(GDBPORT)"; fi)
-QEMUOPTS = -smp 2 -hdb fs.img xv6.img
+ifndef CPUS
+CPUS := 2
+endif
+QEMUOPTS = -hdb fs.img xv6.img -smp $(CPUS)
 
 qemu: fs.img xv6.img
        $(QEMU) -serial mon:stdio $(QEMUOPTS)