On 04/19/2010 12:54 AM, Avi Kivity wrote:
On 04/19/2010 01:51 PM, Peter Zijlstra wrote:
Right, so on x86 we have:
X86_FEATURE_CONSTANT_TSC, which only states that TSC is frequency
independent, not that it doesn't stop in C states and similar fun
stuff.
X86_FEATURE_TSC_RELIABLE, which IIRC should indicate the TSC is
constant
and synced between cores.
Sockets and boards too? (IOW, how reliable is TSC_RELIABLE)?
Not sure, IIRC we clear that when the TSC sync test fails, eg when we
mark the tsc clocksource unusable.
Worrying. By the time we detect this the guest may already have
gotten confused by clocks going backwards.
Upstream, we are marking the TSC unstable preemptively when hardware
which will eventually sync test is detected, so this should be fine.
Zach
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