[patch 17/18] KVM: x86: require matched TSC offsets for master clock

2012-11-19 Thread Marcelo Tosatti
With master clock, a pvclock clock read calculates: ret = system_timestamp + [ (rdtsc + tsc_offset) - tsc_timestamp ] Where 'rdtsc' is the host TSC. system_timestamp and tsc_timestamp are unique, one tuple per VM: the master clock. Given a host with synchronized TSCs, its obvious that guest

[patch 17/18] KVM: x86: require matched TSC offsets for master clock

2012-11-14 Thread Marcelo Tosatti
With master clock, a pvclock clock read calculates: ret = system_timestamp + [ (rdtsc + tsc_offset) - tsc_timestamp ] Where 'rdtsc' is the host TSC. system_timestamp and tsc_timestamp are unique, one tuple per VM: the master clock. Given a host with synchronized TSCs, its obvious that guest