x86: Add support for m5ops through a memory mapped interface

In order to support m5ops in virtualized environments, we need to use
a memory mapped interface. This changeset adds support for that by
reserving 0xFFFF0000-0xFFFFFFFF and mapping those to the generic IPR
interface for m5ops. The mapping is done in the
X86ISA::TLB::finalizePhysical() which means that it just works for all
of the CPU models, including virtualized ones.

util/m5/Makefile.x86

@@ -31,7 +31,7 @@ CC=gcc
 AS=as
 LD=ld
 
-CFLAGS=-O2 
+CFLAGS=-O2 -DM5OP_ADDR=0xFFFF0000
 OBJS=m5.o m5op_x86.o
 
 all: m5

util/m5/m5.c

@@ -51,10 +51,15 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
 #include <unistd.h>
 
 #include "m5op.h"
 
+void *m5_mem = NULL;
+
 char *progname;
 char *command = "unspecified";
 void usage();
@@ -315,6 +320,26 @@ usage()
     exit(1);
 }
 
+static void
+map_m5_mem()
+{
+#ifdef M5OP_ADDR
+    int fd;
+
+    fd = open("/dev/mem", O_RDWR | O_SYNC);
+    if (fd == -1) {
+        perror("Can't open /dev/mem");
+        exit(1);
+    }
+
+    m5_mem = mmap(NULL, 0x10000, PROT_READ | PROT_WRITE, MAP_SHARED, fd, M5OP_ADDR);
+    if (!m5_mem) {
+        perror("Can't mmap /dev/mem");
+        exit(1);
+    }
+#endif
+}
+
 int
 main(int argc, char *argv[])
 {
@@ -322,6 +347,8 @@ main(int argc, char *argv[])
     if (argc < 2)
         usage(1);
 
+    map_m5_mem();
+
     command = argv[1];
 
     argv += 2;

util/m5/m5op_x86.S

@@ -32,6 +32,24 @@
 
 #include "m5ops.h"
 
+#ifdef M5OP_ADDR
+/* Use the memory mapped m5op interface */
+#define TWO_BYTE_OP(name, number)         \
+        .globl name;                      \
+        .func name;                       \
+name:                                     \
+        mov m5_mem, %r11;                 \
+        mov $number, %rax;                \
+        shl $8, %rax;                     \
+        mov 0(%r11, %rax, 1), %rax;       \
+        ret;                              \
+        .endfunc;
+
+#else
+/* Use the magic instruction based m5op interface. This does not work
+ * in virtualized environments.
+ */
+
 #define TWO_BYTE_OP(name, number)         \
         .globl name;                      \
         .func name;                       \
@@ -41,6 +59,8 @@ name:                                     \
         ret;                              \
         .endfunc;
 
+#endif
+
 TWO_BYTE_OP(arm, arm_func)
 TWO_BYTE_OP(quiesce, quiesce_func)
 TWO_BYTE_OP(quiesceNs, quiescens_func)