Index: vl.c
===================================================================
RCS file: /cvsroot/qemu/qemu/vl.c,v
retrieving revision 1.197
diff -u -r1.197 vl.c
--- vl.c	27 Jun 2006 21:02:43 -0000	1.197
+++ vl.c	11 Jul 2006 21:07:35 -0000
@@ -23,6 +23,7 @@
  */
 #include "vl.h"
 
+#include <err.h>
 #include <unistd.h>
 #include <fcntl.h>
 #include <signal.h>
@@ -157,6 +158,10 @@
 int acpi_enabled = 1;
 int fd_bootchk = 1;
 
+#if !(defined TARGET_I386) || !(defined __linux__)
+#define USE_RDTSC
+#endif
+
 /***********************************************************/
 /* x86 ISA bus support */
 
@@ -515,7 +520,33 @@
 
 #elif defined(__i386__)
 
-int64_t cpu_get_real_ticks(void)
+#ifndef USE_RDTSC
+#include <unistd.h>
+#include <sys/io.h>
+#define ACPI_PM_TMR_FREQ 3579545
+
+static uint32_t acpi_prev_ticks;
+static uint32_t acpi_max_ticks;
+static uint32_t acpi_pm_tmr_addr;
+static int64_t acpi_old_ticks;
+
+static int64_t acpi_get_ticks(void)
+{
+    uint32_t ticks = inl_p (acpi_pm_tmr_addr);
+    uint32_t prev = acpi_prev_ticks;
+
+    acpi_prev_ticks = ticks;
+    if (ticks < prev)
+        ticks += (acpi_max_ticks - prev);
+    acpi_old_ticks += ticks;
+    return acpi_old_ticks;
+}
+int64_t (*cpu_get_real_ticks)(void);
+#else
+#define cpu_get_real_ticks rdtsc_get_ticks
+#endif
+
+static int64_t rdtsc_get_ticks(void)
 {
 #ifdef _WIN32
     LARGE_INTEGER ti;
@@ -5597,6 +5628,97 @@
 
 #define MAX_NET_CLIENTS 32
 
+#ifdef USE_RDTSC
+#define acpi_calibrate_ticks cpu_calibrate_ticks
+#else
+static void acpi_calibrate_ticks(void)
+{
+    int fd;
+    ssize_t nread;
+    uint32_t flags;
+    off_t off;
+    int err;
+    uid_t uid;
+
+    uid = getuid ();
+    if (uid == (uid_t) -1) {
+        warn ("could not get user id");
+        goto std_calibrate1;
+    }
+
+    err = setuid (0);
+    if (err) {
+        warn ("could not setuid 0");
+        goto std_calibrate1;
+    }
+
+    fd = open ("/proc/acpi/fadt", O_RDONLY);
+    if (fd < 0) {
+        warn ("could not open fadt");
+        goto std_calibrate;
+    }
+
+    off = lseek (fd, 76, SEEK_SET);
+    if (off - 76) {
+        warn ("could not seek");
+        goto std_calibrate;
+    }
+
+    nread = read (fd, &acpi_pm_tmr_addr, 4);
+    if (nread - 4) {
+        warn ("could not read pm timer io port address nread=%d", nread);
+        goto std_calibrate;
+    }
+
+    off = lseek (fd, 112, SEEK_SET);
+    if (off - 112) {
+        warn ("could not seek");
+        goto std_calibrate;
+    }
+
+    nread = read (fd, &flags, 4);
+    if (nread - 4) {
+        warn ("could not read pm timer facp flags nread=%d", nread);
+        goto std_calibrate;
+    }
+
+    if (!(flags & (1 << 8)))
+        acpi_max_ticks = (1 << 24) - 1;
+    else
+        acpi_max_ticks = ~0U;
+
+    err = close (fd);
+    if (err)
+        warn ("could not close fadt");
+
+    if (iopl (3)) {
+        warn ("could not change iopl");
+        goto std_calibrate2;
+    }
+
+    err = setuid (uid);
+    if (err)
+        warn ("could not restore uid");
+
+    ticks_per_sec = ACPI_PM_TMR_FREQ;
+    cpu_get_real_ticks = &acpi_get_ticks;
+    return;
+
+ std_calibrate:
+    err = close (fd);
+    if (err)
+        warn ("could not close fadt");
+ std_calibrate2:
+    err = setuid (uid);
+    if (err)
+        warn ("could not restore uid");
+ std_calibrate1:
+    fprintf (stderr, "falling back on rdtsc clock\n");
+    cpu_get_real_ticks = &rdtsc_get_ticks;
+    cpu_calibrate_ticks();
+}
+#endif
+
 int main(int argc, char **argv)
 {
 #ifdef CONFIG_GDBSTUB
@@ -6128,7 +6250,7 @@
     register_savevm("ram", 0, 1, ram_save, ram_load, NULL);
 
     init_ioports();
-    cpu_calibrate_ticks();
+    acpi_calibrate_ticks();
 
     /* terminal init */
     if (nographic) {