Allow customizing root and read-write kernel command line options

Author: gsingh93

Makefile

@@ -333,6 +333,8 @@ INITRD ?=
 RDINIT ?= /sbin/init
 QEMU_KERNEL_IMAGE ?= $(KERNEL_IMAGE)
 ECHR ?= 1
+ROOT ?= /dev/vda
+RW ?= rw
 
 QEMU_ARGS := \
   -m $(MEM) \
@@ -353,7 +355,7 @@ ifneq ($(INITRD),)
   QEMU_ARGS += -initrd $(INITRD)
 else
   QEMU_ARGS += -drive file=$(ROOTFS),if=virtio,format=$(ROOTFS_FORMAT)
-  QEMU_EXTRA_KERNEL_CMDLINE += root=/dev/vda rw
+  QEMU_EXTRA_KERNEL_CMDLINE += root=$(ROOT) $(RW)
 endif
 
 ifeq ($(GDB),1)
@@ -364,7 +366,7 @@ ifeq ($(ARCH),x86_64)
   QEMU_BIN := qemu-system-x86_64
   QEMU_ARGS += \
     -cpu kvm64,+smep,+smap \
-    -append "8250.nr_uarts=1 console=ttyS0 selinux=0 kpti no5lvl $(QEMU_EXTRA_KERNEL_CMDLINE)"
+    -append "console=ttyS0 selinux=0 kpti no5lvl $(QEMU_EXTRA_KERNEL_CMDLINE)"
 
   # We can't use KVM with GitHub Actions CI
   ifneq ($(CI),true)