On 04/24/2010 12:31 AM, Zachary Amsden wrote:
On 04/22/2010 11:34 PM, Avi Kivity wrote:
On 04/23/2010 04:44 AM, Zachary Amsden wrote:
Or apply this patch.
time-warp.patch
diff -rup a/time-warp-test.c b/time-warp-test.c
--- a/time-warp-test.c 2010-04-15 16:30:13.955981607 -1000
+++ b/time-warp-test.c 2010-04-15 16:35:37.777982377 -1000
@@ -91,7 +91,7 @@ static inline unsigned long long __rdtsc
{
DECLARE_ARGS(val, low, high);
- asm volatile("cpuid; rdtsc" : EAX_EDX_RET(val, low, high));
+ asm volatile("cpuid; rdtsc" : EAX_EDX_RET(val, low, high) ::
"ebx", "ecx");
Plus, replace cpuid by lfence/mfence. cpuid will trap.
Does lfence / mfence actually serialize? I thought there was some
great confusion about that not being the case on all AMD processors,
and possibly not at all on Intel.
They don't.
A trap, however is a great way to serialize.
I think, there is no serializing instruction which can be used from
userspace which does not trap, at least, I don't know one off the top
of my head.
iret.
--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.
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