feature/qemu-config - Add config parameter to Makefile

Makefile

@@ -1,6 +1,13 @@
 K=kernel
 U=user
 
+# 128M is the default for xv6 - Warning no trailing space after the number
+RAM=128
+# 3 is the default for xv6
+CPUCOUNT=3
+
+
+
 OBJS = \
   $K/entry.o \
   $K/start.o \
@@ -59,6 +66,8 @@ OBJDUMP = $(TOOLPREFIX)objdump
 CFLAGS = -Wall -Werror -O -fno-omit-frame-pointer -ggdb -gdwarf-2
 CFLAGS += -MD
 CFLAGS += -mcmodel=medany
+CFLAGS += -DMAXMEM=$(RAM)
+CFLAGS += -DNCPU=$(CPUCOUNT)
 # CFLAGS += -ffreestanding -fno-common -nostdlib -mno-relax
 CFLAGS += -fno-common -nostdlib
 CFLAGS += -fno-builtin-strncpy -fno-builtin-strncmp -fno-builtin-strlen -fno-builtin-memset
@@ -160,10 +169,10 @@ QEMUGDB = $(shell if $(QEMU) -help | grep -q '^-gdb'; \
 	then echo "-gdb tcp::$(GDBPORT)"; \
 	else echo "-s -p $(GDBPORT)"; fi)
 ifndef CPUS
-CPUS := 3
+CPUS := $(CPUCOUNT)
 endif
 
-QEMUOPTS = -machine virt -bios none -kernel $K/kernel -m 128M -smp $(CPUS) -nographic
+QEMUOPTS = -machine virt -bios none -kernel $K/kernel -m $(RAM)M -smp $(CPUS) -nographic
 QEMUOPTS += -global virtio-mmio.force-legacy=false
 QEMUOPTS += -drive file=fs.img,if=none,format=raw,id=x0
 QEMUOPTS += -device virtio-blk-device,drive=x0,bus=virtio-mmio-bus.0

kernel/entry.S

@@ -1,3 +1,4 @@
+#include "param.h"
         # qemu -kernel loads the kernel at 0x80000000
         # and causes each hart (i.e. CPU) to jump there.
         # kernel.ld causes the following code to
@@ -7,10 +8,10 @@
 _entry:
         # set up a stack for C.
         # stack0 is declared in start.c,
-        # with a 4096-byte stack per CPU.
-        # sp = stack0 + (hartid * 4096)
+        # with a CPUSTACKSIZE-kilobytes stack per CPU as definied in param.h.
+        # sp = stack0 + ((hartid + 1) * CPUSTACKSIZE)
         la sp, stack0
-        li a0, 1024*4
+        li a0, 1024 * CPUSTACKSIZE
         csrr a1, mhartid
         addi a1, a1, 1
         mul a0, a0, a1

kernel/kalloc.c

@@ -28,6 +28,8 @@ kinit()
 {
   initlock(&kmem.lock, "kmem");
   freerange(end, (void*)PHYSTOP);
+  // Output the start and end of Memory to see if change to RAM parameter in Makefile has an effect
+  printf("kinit: Memory start addr: %p,  Memory end addr:%p\n",end, (void*)PHYSTOP);
 }
 
 void

kernel/memlayout.h

@@ -37,7 +37,7 @@
 // for use by the kernel and user pages
 // from physical address 0x80000000 to PHYSTOP.
 #define KERNBASE 0x80000000L
-#define PHYSTOP (KERNBASE + 128*1024*1024)
+#define PHYSTOP (KERNBASE + MAXMEM*1024*1024)
 
 // map the trampoline page to the highest address,
 // in both user and kernel space.

kernel/param.h

@@ -1,5 +1,5 @@
+#define CPUSTACKSIZE  4 // Stacksize in KB per CPU - Currently leave on 4 KB this is xv6 default
 #define NPROC        64  // maximum number of processes
-#define NCPU          8  // maximum number of CPUs
 #define NOFILE       16  // open files per process
 #define NFILE       100  // open files per system
 #define NINODE       50  // maximum number of active i-nodes
@@ -13,3 +13,6 @@
 #define MAXPATH      128   // maximum file path name
 #define USERSTACK    1     // user stack pages
 
+// Defined in Makefile, so it is dynamic based on the config for qemu
+//#define NCPU          8  // maximum number of CPUs
+//#define MAXMEM       128   // max Memory in megabyte

kernel/start.c

@@ -8,7 +8,7 @@ void main();
 void timerinit();
 
 // entry.S needs one stack per CPU.
-__attribute__ ((aligned (16))) char stack0[4096 * NCPU];
+__attribute__ ((aligned (16))) char stack0[1024 * CPUSTACKSIZE * NCPU];
 
 // entry.S jumps here in machine mode on stack0.
 void