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answered Oct 12, 2011 at 19:58Its common to use RDTSC to get fine-grained timing information, where the overhead of a virtualization trap would be quite significant. Most common use is to have two RDTSC instructions with a small amount of code between them, taking the difference of the times as the elapsed time (number of cycles) for the code sequence. So even the overhead of pipeline drains/flushes is quite significant.
Also, since all the instruction does is read a continuously running counter, virtualizing it is quite easy -- the hardware only needs to allow saving/relo...
Content Under CC-BY-SA license Timekeeping Virtualization for X86-Based Architectures
WebVMX provides conditional trapping of RDTSC, RDMSR, WRMSR and RDTSCP instructions, which is enough for full virtualization of TSC in any manner. In addition, VMX allows passing through the host TSC plus an additional TSC
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Why is RDTSC a virtualized instruction on modern processors?
WebOct 12, 2011 · Its common to use RDTSC to get fine-grained timing information, where the overhead of a virtualization trap would be quite significant. Most common use is to have two RDTSC instructions with a small amount of code between
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WebOn x86 platforms the rdtsc and rdtscp instructions gave us the ability to access a internal 64-bit hardware time stamp counter TSC (Time Stamp Counter) that is reset to zero at boot time and since then increments at a certain frequency (ideally at the same rate as the processor clock speed), which can be very useful for conducting microbenchmarks.
An introduction to timekeeping in Linux VMs | Opensource.com
- Since the early days of hardware-assisted virtualization, Intel was supplying an option to do TSC offsetting for virtual guests in hardware, which would mean that a guest's rdtsc reading will return a host's TSC value + offset. Unfortunately, this wasn't enough to support migration between different hosts because TSC frequency may differ, so pvcloc...
RDTSC | x86 Instruction Set Reference
WebApr 18, 2019 · Description. Loads the current value of the processor's time-stamp counter into the EDX:EAX registers. The time-stamp counter is contained in a 64-bit MSR. The high-order 32 bits of the MSR are loaded into the EDX register, and the low-order 32 bits are loaded into the EAX register.
Resurrecting anti-virtualization and anti-debugging: Unhooking ...
WebMar 1, 2021 · This is accomplished in ANTI by using the RDTSC instruction and the NtQueryPerformanceCounter Native API function. The RDTSC (Read Time Stamp Counter) instruction returns the current value of the timestamp counter from the processor, while NtQueryPerformanceCounter retrieves the current value of the performance counter.
Clocks, Timers and Virtualization :: silly onions ...
WebJul 12, 2020 · In both Intel VT-x and AMD SVM, the TSC can be fully virtualized by trapping the RDTSC, RDMSR, WRMSR and RDTSCP instructions [5]. Also, it is possible to pass through the host TSC to the virtual machine. Both trapping and
WebIn this paper, we present analysis results for RDTSC usage collected from more than 200,000 malware files. In this analysis, malware programs are searched for closely placed pairs of RDTSCs; then, code fragments surrounding these pairs are extracted.
WebThis feature, referred to as timestamp-counter scaling (TSC scaling), further extends the capability of virtual-machine monitor (VMM) softwa re that employs the TSC-offsetting mechanism by allowing that software finer control over the value of the timestamp counter (TSC) read during guest virtual machine (VM) execution.
__rdtsc | Microsoft Learn
WebAug 2, 2021 · Generates the rdtsc instruction, which returns the processor time stamp. The processor time stamp records the number of clock cycles since the last reset. Syntax unsigned __int64 __rdtsc(); Return value A 64-bit unsigned
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