On Tue, Jan 14, 2020 at 12:30:02AM +0100, Rafael J. Wysocki wrote: > On Mon, Jan 13, 2020 at 10:50 PM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote: > > > > On Mon, Jan 13, 2020 at 1:43 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > > > > On Mon, Jan 13, 2020 at 11:43:18AM +0000, Singh, Balbir wrote: > > > > For your original comment, just wanted to clarify the following: > > > > > > > > 1. After hibernation, the machine can be resumed on a different but compatible > > > > host (these are VM images hibernated) > > > > 2. This means the clock between host1 and host2 can/will be different > > > > > > > > In your comments are you making the assumption that the host(s) is/are the > > > > same? Just checking the assumptions being made and being on the same page with > > > > them. > > > > > > I would expect this to be the same problem we have as regular suspend, > > > after power off the TSC will have been reset, so resume will have to > > > somehow bridge that gap. I've no idea if/how it does that. > > > > In general, this is done by timekeeping_resume() and the only special > > thing done for the TSC appears to be the tsc_verify_tsc_adjust(true) > > call in tsc_resume(). > > And I forgot about tsc_restore_sched_clock_state() that gets called > via restore_processor_state() on x86, before calling > timekeeping_resume(). > In this case tsc_verify_tsc_adjust(true) this does nothing as feature bit X86_FEATURE_TSC_ADJUST is not available to guest. I am no expert in this area, but could this be messing things up? Thanks, Anchal
