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Re: cpu_counter_serializing() vs. QEMU

On 6/20/13 7:26 PM, Masao Uebayashi wrote:
Intel(R) 64 and IA-32 Architectures Software Developer’s Manual
Volume 3 (3A, 3B & 3C): System Programming Guide

     TSC flag - A feature bit that indicates the availability of the
time-stamp counter.
     The counter is available in an if the function CPUID.1:EDX.TSC[bit 4] = 1.

We're already doing this check - I think the problem stems from the fact that QEMU doesn't implement the MSR - it *does* seem to implement rdtsc, though, which seems to be a non-serializing version. Are you suggesting we should disable TSC entirely for QEMU? How will this affect non-serializing uses?

On Fri, Jun 21, 2013 at 7:10 AM, Jeff Rizzo <riz%tastylime.net@localhost> wrote:

- is testing (cpu_feature[0] & CPUID_MSR) the right test?  Only some MSRs
are implemented.
I don't think so.

Should we be inventing some new test for "partial TSC support"? Should we just disable TSC in QEMU entirely?


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