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Re: [Xen-devel] Could you please answer some questions regarding Solaris PVHVM pvclock support.

ä 2014/2/27 21:03, Stefano Stabellini åé:
>I guest linux guest will do the same thing, rdtsc() fetch current timestamp 
from current running vCPU, TSC out-of-sync issue is still there.
>It seems to me pvclock finally fix the time drift issue just because the 
workaround enforced as above, right?
First you should know that TSC is not always guaranteed to be
synchronized across multiple processors, especially on older systems.
On "TSC-safe" systems, Xen would export a consistent TSC to guests, by
setting the vtsc offset and scale appropriately.

Is there a easy way to check whether the system is "TSC-safe"? Do you mean "X86_FEATURE_TSC_RELIABLE" bit in "boot_cpu_data.x86_capability"?


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