Timer access from user mode through a shared memory page

A computer system, comprising:

• at least one physical processor;
• a computer-readable medium encoded with computer-executable instructions implementing a hypervisor, the hypervisor emulating an emulated processor having a time stamp counter;
• and
• a computer-readable medium encoded with computer-executable instructions implementing a computer operating system executing on the emulated processor;
• and
• a computer-readable medium encoded with computer-executable instructions implementing a user mode component executing on the computer operating system that performs a method of computing a normalized reference time, the method comprising:
• operating the at least one physical processor to execute the computer-executable instructions of the user mode component the operating comprising:
• reading a timer value from the time stamp counter from the emulated processor;
• obtaining through an interface with the hypervisor a scale factor and an offset;
• and
• calculating the normalized reference time by applying the offset and the scale factor to the value obtained from the time stamp counter.

A computer-readable medium encoded with computer-executable instructions, that when executed on a computer, the computer comprising an operating system executing on a hypervisor, the hypervisor emulating an emulated processor having a time stamp counter, performs a method of computing a normalized reference time in a user-level component executing on the operating system, the method comprising:

• operating the at least one physical processor to execute the computer-executable instructions of the user mode component, the operating comprising:
• reading a timer value from the time stamp counter from the emulated processor;
• obtaining through an interface with a kernel of the operating system a scale factor and an offset;
• and
• calculating the normalized reference time by applying the offset and the scale factor to the value obtained from the time stamp counter.