[Qemu-devel] [PATCH] icount: disable icount with multiprocessor guests

[Paolo Bonzini <pbonzini@redhat.com>]

If -icount is enabled with multiprocessor guests, all CPUs increment
the same counter, which then basically runs too fast by a factor of
smp_cpus.  This makes little sense and complicates further a feature
whose implementation is pretty obscure already.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 cpus.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/cpus.c b/cpus.c
index 6fb2bc8..e74166e 100644
--- a/cpus.c
+++ b/cpus.c
@@ -401,6 +401,11 @@ void configure_icount(const char *option)
         return;
     }
 
+    if (smp_cpus > 1) {
+        fprintf(stderr, "-icount is not allowed with SMP guests\n");
+        exit(1);
+    }
+
     icount_warp_timer = timer_new_ns(QEMU_CLOCK_REALTIME,
                                           icount_warp_rt, NULL);
     if (strcmp(option, "auto") != 0) {
-- 
1.8.3.1