Lines Matching refs:time

19 time introduces a new set of challenges because it introduces a multiplexed
20 division of time beyond the control of the guest CPU.
183 time clock.  The original device is now obsolete, and usually emulated by the
197 The RTC will update the current time fields by battery power even while the
198 system is off.  The current time fields should not be read while an update is
293 time source which is independent of local variation (as there is only one HPET
308 not considered important at this time as no known operating system does this.
314 The TSC or time stamp counter is relatively simple in theory; it counts
316 time.  In practice, due to a number of problems, it is the most complicated
362 As touched on already, CPUs which arrive later than the boot time of the system
376 cause the CPU clocks, and thus the TSCs to drift over time.  Depending on the
378 error, and may accumulate over time.
403 may be staggered or slewed, at some points in time, the TSC rate may not be
405 not be a stable time source, and must be calibrated against a known, stable,
406 external clock to be a usable source of time.
460 challenges arise.  The most obvious problem is that time is now shared between
466 at any time.  This causes problems as the passage of real time, the injection
468 synchronized with real time.
480 time by counting periodic interrupts.  These interrupts may come from the PIT
483 time may fall behind.  This is especially problematic if a high interrupt rate
488 to simply ignore it.  Guests which have a separate time source for tracking
489 'wall clock' or 'real time' may not need any adjustment of their interrupts to
490 maintain proper time.  If this is not sufficient, it may be necessary to inject
500 Windows uses periodic RTC clocking as a means of keeping time internally, and
501 thus requires interrupt slewing to keep proper time.  It does use a low enough
507 As the highest precision time source available, the cycle counter of the CPU
522 accurate time stamp counter reading may therefore not always be available, and
530 when using results of the TSC when measured against another time source.  As
536 fluctuates - from (T-1.. T+10).  Thus, any time calculated from a TSC, but
538 Re-calibrating this computation may actually cause time, as computed after the
539 calibration, to go backwards, compared with time computed before the
542 This problem is particularly pronounced with an internal time source in Linux,
543 the kernel time, which is expressed in the theoretically high resolution
554 First, the migration itself may take time, during which interrupts cannot be
555 delivered, and after which, the guest time may need to be caught up.  NTP may
563 faster clock cannot be made visible to a guest without the potential of time
579 paravirtualized scheduler clock, which reveals the true amount of CPU time for
586 misinterpretation of the passage of real time.  Usually, these warnings are
596 adequately virtualized without a full real-time operating system, which would
605 In addition to the above problems, time information will inevitably leak to the
607 time.  This may allow the guest to infer the presence of a hypervisor (as in a
610 problems would require completely isolated virtual time which may not track
611 real time any longer.  This may be useful in certain security or QA contexts,