Re: [Qemu-devel] QEMU News

[renzo@cs.unibo.it (Renzo Davoli)]

[-- Attachment #1: Type: text/plain, Size: 619 bytes --]

On Wed, Mar 31, 2004 at 09:14:54PM +0200, Fabrice Bellard wrote:
> - Timer API for the device drivers (similar to the Linux kernel timers). 
> It will enable the use of a virtual cycle counter to have a fully 
> deterministic emulation (useful for debugging).

There is a bug. On a P4 I have got a SIGFPE.
The fix is here attached. 
The asm call inside cpu_get_real_ticks (file vl.c) must be defined
volatile.
It seems that otherwise somewhere (gcc?) a code optimization instead
of evaluating twice the same instruction takes the former output value,
thus the count of tick per seconds results to be zero.

ciao
	renzo

[-- Attachment #2: vl.c.patch --]
[-- Type: text/plain, Size: 266 bytes --]

--- vl.c.orig	2004-04-01 10:44:57.000000000 +0200
+++ vl.c	2004-04-01 10:38:25.000000000 +0200
@@ -341,7 +341,7 @@
 int64_t cpu_get_real_ticks(void)
 {
     int64_t val;
-    asm("rdtsc" : "=A" (val));
+    asm volatile ("rdtsc" : "=A" (val));
     return val;
 }